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Messenger RNA is a powerful, if fickle, component of life’s building blocks — a workhorse of the cell that is also truly just a messenger, unstable and prone to degrade.

. In 1990,

That same year, a team at the University of Wisconsin startled the scientific world with a paper that showed it was possible to inject a snippet of messenger RNA into mice and turn their muscle cells into factories, creating proteins on demand.

If custom-designed RNA snippets could be used to turn cells into bespoke protein factories, messenger RNA could become a powerful medical tool. It could encode fragments of virus to teach the immune system to defend against pathogens. It could also create whole proteins that are missing or damaged in people with devastating genetic diseases, such as cystic fibrosis.

In 2005, the pair discovered a way to modify RNA, chemically tweaking one of the letters of its code, so it didn’t trigger an inflammatory response. Deborah Fuller, a scientist who works on RNA and DNA vaccines at the University of Washington, said that work deserves a Nobel Prize.

messenger RNA posed a bigger challenge than other targets.“It’s tougher — it’s a much bigger molecule, it’s much more unstable,”

Unlike fields that were sparked by a single powerful insight, Sahin said that the recent success of messenger RNA vaccines is a story of countless improvements that turned an alluring biological idea into a beneficial technology.

“This is a field which benefited from hundreds of inventions,” said Sahin, who noted that when he started BioNTech in 2008, he cautioned investors that the technology would not yield a product for at least a decade. He kept his word: Until the coronavirus sped things along, BioNTech projected the launch of its first commercial project in 2023.

“It’s new to you,” Fuller said. “But for basic researchers, it’s been long enough. . . . Even before covid, everyone was talking: RNA, RNA, RNA.”

All vaccines are based on the same underlying idea: training the immune system to block a virus. Old-fashioned vaccines do this work by injecting dead or weakened viruses

ewer vaccines use distinctive bits of the virus, such as proteins on their surface, to teach the lesson. The latest genetic techniques, like messenger RNA, don’t take as long to develop because those virus bits don’t have to be generated in a lab. Instead, the vaccine delivers a genetic code that instructs cells to build those characteristic proteins themselves.

Severe acute respiratory syndrome had emerged in 2003. Middle East respiratory syndrome (MERS) broke out in 2012. It seemed clear to Graham and Jason McLellan, a structural biologist now at the University of Texas at Austin, that new coronaviruses were jumping into people on a 10-year-clock and it might be time to brace for the next one.

That infection opened Graham’s eyes to an opportunity. HKU1 was merely a nuisance, as opposed to a deadly pneumonia; that meant it would be easier to work with in the lab, since researchers wouldn’t have to don layers of protective gear and work in a pressurized laboratory.

They wanted the immune system to learn to recognize the thumb tack spike, so McLellan tasked a scientist in his laboratory with identifying genetic mutations that could anchor the protein into the right configuration. It was a painstaking process for Nianshuang Wang, who now works at a biotechnology company, Regeneron Pharmaceuticals. After trying hundreds of genetic mutations, he found two that worked. Five journals rejected the finding, questioning its significance, before it was published in 2017.

Last winter, when Graham heard rumblings of a new coronavirus in China, he brought the team back together. Once its genome was shared online by Chinese scientists, the laboratories in Texas and Maryland designed a vaccine, utilizing the stabilizing mutations and the knowledge they had gained from years of basic research — a weekend project thanks to the dividends of all that past work.

Graham needed a technology that could deliver it into the body — and had already been working with Moderna, using its messenger RNA technology to create a vaccine against a different bat virus, Nipah, as a dress rehearsal for a real pandemic. Moderna and NIH set the Nipah project aside and decided to go forward with a coronavirus vaccine.

On Jan. 13, Moderna’s Moore came into work and found her team already busy translating the stabilized spike protein into their platform. The company could start making the vaccine almost right away because of its experience manufacturing experimental cancer vaccines, which involves taking tumor samples and developing personalized vaccines in 45 days.

At BioNTech, Sahin said that even in the early design phases of its vaccine candidates, he incorporated the slight genetic changes designed in Graham’s lab that would make the spike look more like the real thing. At least two other companies would incorporate that same spike.

If all goes well with regulators, the coronavirus vaccines have the makings of a pharmaceutical industry fairy tale. The world faced an unparalleled threat, and companies leaped into the fight. Pfizer plowed $2 billion into the effort. Massive infusions of government cash helped remove the financial risks for Moderna.

But the world will also owe their existence to many scientists outside those companies, in government and academia who pursued ideas they thought were important even when the world doubted them

“They’re using the technology that [Kariko] and I developed,” he said. “We feel like it’s our vaccine, and we are incredibly excited — at how well it’s going, and how it’s going to be used to get rid of this pandemic.”

As executives become billionaires, many scientists think it is fair to earn money from their inventions that can help them do more important work. But McLellan’s laboratory at the University of Texas is proud to have licensed an even more potent version of their spike protein, royalty-free, to be incorporated into a vaccine for low and middle income countries.

Some of those scientists will receive remuneration, since their inventions are licensed and integrated into the products that could save the world.

“People hear about [vaccine progress] and think someone just thought about it that night. The amount of work — it’s really a beautiful story of fundamental basic research,” Fauci said. “It was chancy, in the sense that [the vaccine technology] was new. We were aware there would be pushback. The proof in the pudding is a spectacular success.”

The Vaccine Research Center, where Graham is deputy director, was the brainchild of Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases. It was created in 1997 to bring together scientists and physicians from different disciplines to defeat diseases, with a heavy focus on HIV.

the pandemic wasn’t a sudden eureka moment — it was a catalyst that helped ignite lines of research that had been moving forward for years, far outside the spotlight of a global crisis.

“Sometimes, I feel like we’re practicing in the 1950s,” said Dr. Eric Ball, a pediatrician in southern Orange County, where some schools report that 50 to 60 percent of their kindergartners are not fully vaccinated and that 20 to 40 percent of parents have sought a personal beliefs exemption to vaccination requirements. “It’s very frustrating. It’s hard to see a kid suffer for something that’s entirely preventable.”

Dr. Ball said he spent many days trying to persuade parents to vaccinate their children. He tries to alleviate their concerns. He shows parents his own children’s vaccine records. But it has not worked, and lately, as worries and anger over this outbreak have spread, some families who support vaccines have said they do not want to be in the same waiting room as unvaccinated families. The clinic where Dr. Ball works has treated unvaccinated children for years, but its staff is meeting next week to discuss a ban.“Our patients are really scared,” Dr. Ball said. “Our nightmare would be for someone to show up at our door with the measles.”

Norm Warren, the manager of the supermarket in Kearny, Gordon’s IGA, has changed his thinking toward those who do not vaccinate their children.“Before, I thought, ‘If you think your child will become autistic, fine.’ But now they’re pushing their beliefs on everybody, and I feel differently,“ he said. “How many lives have been saved by vaccination?“

Members of the anti-vaccine movement said the public backlash had terrified many parents. “People are now afraid they’re going to be jailed,” said Barbara Loe Fisher, the president of the National Vaccine Information Center, a clearinghouse for resisters. “I can’t believe what I’m seeing. It’s gotten so out of hand, and it’s gotten so vicious.”

In San Geronimo, Calif., a mostly rural community of rolling hills and oak trees about 30 miles north of San Francisco, 40 percent of the students walking into Lagunitas Elementary School have not been inoculated against measles, according to the school’s figures. Twenty-five percent have not been vaccinated for polio. In all, the state says that 58 percent of Lagunitas kindergartners do not have up-to-date vaccine records.

“A lot of people here have personal beliefs that are faith based,” said John Carroll, the school superintendent, who sent a letter home to parents last week encouraging them to vaccinate their children. The faith, Mr. Carroll said, is not so much religious as it is a belief that “they raise their children in a natural, organic environment” and are suspicious of pharmaceutical companies and big business.

Some parents forgo shots altogether. Others split vaccine doses or stretch out their timeline, worried about somehow overwhelming their children’s immune system. Kelly McMenimen, a Lagunitas parent, said she “meditated on it a lot” before deciding not to vaccinate her son Tobias, 8, against even “deadly or deforming diseases.” She said she did not want “so many toxins” entering the slender body of a bright-eyed boy who loves math and geography.

Tobias has endured chickenpox and whooping cough, though Ms. McMenimen said the latter seemed more like a common cold. She considered a tetanus shot after he cut himself on a wire fence but decided against it: “He has such a strong immune system.”

“It’s good to explore alternatives rather than go with the panic of everyone around you,” she said. “Vaccines don’t feel right for me and my family.”

An overwhelming majority of American adults (88%) say the benefits of the measles, mumps and rubella (MMR) vaccine outweigh the risks, according to a new Pew Research Center survey.And last year, 14 states proposed eliminating religious exemptions for vaccines -- a marked increase from years past, according to the American Academy of Pediatrics.

"When you choose not to vaccinate, you're putting your child at risk of disease, but you're also putting other people at risk," O'Leary said.

"We need to have the ability in our country, if we find a commercial pharmaceutical product is not as safe and effective as we're being told it is, we should have the right to make informed consent to use the product," she said.

"When vaccination rates fall, we see disease, and people suffer. Protecting children in schools is a worthy goal of government, regardless of political affiliation," he said. "There's really no good reason to exempt your child from vaccination -- only medical."

"Science is really on the side of vaccinations," said O'Leary, who is an associate professor of pediatrics at the University of Colorado School of Medicine. "They're one of the best public health interventions in history in terms of the numbers of lives saved. The benefits far outweigh the risk."

New York, California and Washington state took action after massive measles outbreaks in 2019, a year that saw the highest reported measles cases since the disease was declared eliminated nationwide in 2000.

Many of the religious exemption laws are not new. Several states first passed them in the 1960s and 1970s, thanks to an influx of lobbyists from the Christian Science Church, which doesn't ban members from using vaccines but encourages healing through prayer.

Supporters of vaccine exemptions see laws like those passed in New York and Washington as "fundamentally a threat to their ability to make informed consent about vaccinations," said Fisher, president of the National Vaccine Information Center.

Proponents on both sides of the debate have found allies across the political spectrum. Republican lawmakers have sponsored stricter bills, and Democratic governors have drawn the line at mandating vaccines.

"It's a tough balance, but you're using a public -- and private -- resource in conjunction with lots of other kids," Harris told CNN. "There are other venues where they can be educated, they can still have their freedom, but they're not going into a public school and spread their disease."

The agency cites the results of a study in Germany and clinical trials in the U.K. and Spain as supporting the safety of vaccine interchangeability.

As of late May, 50.6% of Canada's population had received at least one vaccination shot — but only 4.6% of the population was fully vaccinated.

"Different vaccine products have been used to complete a vaccine series for influenza, hepatitis A, and others to complete a vaccine series for influenza, hepatitis A, and others."

"Basically, all vaccines work by showing people's immune systems something that looks like an invading virus but really isn't. If the real virus ever comes along, their immune systems will recognize it and be prepared to fight it off.

"Using two different vaccines is a bit like giving the immune system two pictures of the virus, maybe one face-on and one in profile."

"Individuals who have received one dose of the Pfizer-BioNTech or Moderna COVID-19 vaccine should receive a second dose of the same vaccine to complete the vaccination series," the spokesperson added.

“Please be assured that YOU ARE SAFE after vaccine from what matters — disease and spreading.”

The risks for vaccinated people are still not zero, because almost nothing in the real world is zero risk. A tiny percentage of people may have allergic reactions

the evidence so far suggests that the vaccines are akin to a cure.

The Moderna and Pfizer vaccines — the only two approved in the U.S. — are among the best vaccines ever created, with effectiveness rates of about 95 percent after two doses.

That’s on par with the vaccines for chickenpox and measles.

The Moderna and Pfizer vaccines are “essentially 100 percent effective against serious disease,” Dr. Paul Offit, the director of the Vaccine Education Center at Children’s Hospital of Philadelphia, said. “It’s ridiculously encouraging.”

“It’s going to save your life — that’s where the emphasis has to be right now,”

“We’re underselling the vaccine,”

Right now, public discussion of the vaccines is full of warnings about their limitations: They’re not 100 percent effective. Even vaccinated people may be able to spread the virus. And people shouldn’t change their behavior once they get their shots.

These warnings have a basis in truth, just as it’s true that masks are imperfect.

It summarized and condemned the scientific and medical fraud that the British researcher Andrew Wakefield perpetrated. Years earlier, he had falsely linked the measles, mumps, and rubella (MMR) vaccine to autism. The editorial lamented that “the damage to public health continues, fuelled by unbalanced media reporting and an ineffective response from government, researchers, journals, and the medical profession.”

Reporters also seek to ensure that viewers, listeners, or readers understand that measles can afflict a victim more powerfully than does a mere passing ailment.

Measles doesn’t spread in most U.S. communities because people are protected by “herd immunity,” meaning that 92% to 94% of the population is vaccinated or immune. That level of protection makes it hard for one case of measles to spread even from one unvaccinated person to another without direct contact.

a study that “found that only 51 percent of Americans were confident that vaccines are safe and effective, which is similar to the proportion who believe that houses can be haunted by ghosts.”

In some parts of California, resistance to vaccinations including the MMR shot is stronger than ever, despite cases of measles hitting five US states.

“Vaccines are a great idea, but they are poisoning us, adding things that kick in later in life so they can sell us more drugs.”

Health professionals say those claims are unfounded or vastly overstated.

Large outbreaks in the U.S. of the highly infectious disease have become more common in the past two years, even though measles hasn’t been indigenous since 2000, according to the Centers for Disease Control and Prevention.

the outbreak “should worry and enrage the public.” It indicted the anti-vaxxers’ “ignorant and self-absorbed rejection of science” and declared, “Getting vaccinated is good for the health of the inoculated person and also part of one’s public responsibility to help protect the health of others.”

“It’s wrong,” the editors emphasized, “to allow public health to be threatened while everyone else waits for these science-denying parents to open their eyes.”

“It’s because these people are highly educated and they get on the Internet and read things and think they can figure things out better than their physician.”

linked vaccination opposition to the “political left, which has long been suspicious of the lobbying power of the pharmaceutical industry and its influence on government regulators, and also the fringe political right, which has at different times seen vaccination, fluoridisation and other public-health initiatives as attempts by big government to impose tyrannical limits on personal freedom.”

Attempts to increase concerns about communicable diseases or correct false claims about vaccines may be especially likely to be counterproductive.

“attempting balance by giving vaccine skeptics and pro-vaccine advocates equal weight in news stories leads people to believe the evidence for and against vaccination is equally strong.”

A recent edition of the Washington Post carried a letter defending anti-vaxxers as “people who generally are pro-science and highly educated, who have high incomes and who have studied this issue carefully before coming to the conclusion that the risk to their children is greater than the slim possibility of contracting a childhood disease that [in many cases leaves] little or no residual consequences.”

anecdotal evidence suggests that some journalists, rather than omitting anti-vaxxers’ views, prefer to expose them and then oppose them.

“unwarranted fear . . . an assault on one of the greatest public-health inventions in world history.”

Regulatory review and approval. If a medication or drug is proven safe and effective in clinical trials, the U.S. Food and Drug Administration gets involved to evaluate the vaccine and administer an approval. The International Federation of Pharmaceutical Manufacturers and Associations reports that, typically, 1 in 10 experimental vaccines make it all the way through regulatory approval.

Each one of those steps can take years, and a potential vaccine can get stalled indefinitely at any one of them.

Because of the lengthy timeline associated with vaccine development, nearly three dozen companies and academic institutions around the world are now directing resources towards the search

There's not a whole lot that can be done to speed up the process and still arrive at a safe and effective vaccine. Currently, most medical and public health experts say we're at least 12 to 18 months away from having a usable vaccine against COVID-19.

While these new approaches could speed a vaccine to market, it does raise some ethical questions about safety. It's also unclear just yet whether the rush will result in an effective vaccine faster

"In the beginning of the process, the research usually involves searching through tons of sources of data to uncover opportunities that may not be so obvious.

The trial will assess "safety and antibody production, meaning that testing various doses' safety and whether these doses are producing an immune response. This phase 1 trial is not studying the effectiveness of the vaccine in preventing coronavirus infection. That will come at a later phase of the research,

But the sense of urgency surrounding the need for a safe, effective vaccine to prevent COVID-19 is driving public health officials, private pharmaceutical companies and others to work as quickly as they can to find a solution. The sooner these vaccines and other medications can be tested, the sooner we might have a viable vaccine that can halt a global pandemic that shows few signs of slowing on its own. But right now, experts say that it will take at least a year and likely longer before such a vaccine is available

"At this point, the Oxford researchers have no idea whether they have something or not," Offit said. "You just get so tired of this 'science by press release.' "

There are currently 10 vaccines in human clinical trials worldwide, according to the World Health Organization. Four of the teams are in the United States: Moderna, Pfizer, Inovio and Novavax.

Moderna CEO Stéphane Bancel referred to the results as "positive interim Phase 1 data" and that "the Moderna team continues to focus on moving as fast as safely possible to start our pivotal Phase 3 study in July."

Moderna is collaborating on its vaccine development with the National Institute of Allergy and Infectious Diseases. Dr. Anthony Fauci, the director of NIAID, said while Moderna's numbers were limited, "it was good news" and he was "cautiously optimistic" about the vaccine.

Inovio and Moderna have said they expect their large-scale clinical trials, known as Phase 3 trials, to last around six months. Pfizer hasn't given a timetable for its Phase 3 trial.

"I've not seen anyone wrap up a Phase 3 trial in a month to six weeks," said Dr. Saad Omer, a Yale University infectious disease expert who's done clinical trials on polio, pertussis and influenza vaccines. "We need to benchmark this against realistic expectations."

"As vaccine researchers like to say, mice lie and monkeys exaggerate," Offit said.

One big stumbling block for any vaccine trial is that Covid-19 infection rates in many areas of the world are flattening out or declining.

The Oxford vaccine uses what's called an adenovirus vector. Adenoviruses cause the common cold, but in this case, the adenoviruses are weakened and modified to deliver genetic material that codes for a protein from the novel coronavirus. The body then produces that protein and, ideally, develops an immune response to it.

"Compared to previous vaccines, this method is more robust, more versatile, and yet, equally efficient," according to the blog, which notes that the Bill & Melinda Gates Foundation invested $53 million in a German biotech company that specializes in RNA vaccines.

Inovio's technology uses a brief electrical pulse to deliver plasmids, or small pieces of genetic information, into human cells. Inovio says those cells then produce the vaccine, which leads to an immune response.

On April 19, the BBC's Andrew Marr said he asked Gilbert "if it's guaranteed that a workable vaccine can actually be produced."

"Nobody can be absolutely sure it's possible. That's why we have to do trials. We have to find out. I think the prospects are very good, but it's clearly not completely certain,"

"It certainly worked in monkeys," Oxford's Hill told CNN's Burnett May 15. "That was quite an impressive impact and that was our first try, if you like, with a standard dose, a single dose of vaccine."

"I buy that this is a pandemic and we may need to show progress and show steps, and I'm OK with making forecasts if decision makers want that, but do it with a level of uncertainty, because that's what's warranted," said Omer, director of the Yale Institute for Global Health.

"Now researchers can't wait to step out to the microphone -- and there are so many microphones out there -- to say, 'I've got it! This looks really good!' " Offit said.

The guilt I felt about this compelled me to objectively review the literature on mRNA vaccines. Not being an expert in virology or biochemistry, I realized I had to quickly master unfamiliar words like “transfection” and concepts about gene sequences. Slowly, the information I was devouring started changing my beliefs.

I learned that research into using mRNA for vaccinations and cancer therapies has been ongoing for the past 30 years. Trial and error have refined this modality so that it was almost fully fledged by the time Covid hit

The mRNA from the vaccine is broken down quickly in our cells, and the coronavirus spike protein is expressed only transiently on the cell surface.

Furthermore, this type of vaccine is harnessing a technique that viruses already use.

It was humbling to have to change my mind. As I booked my vaccination time slot, I realized how lucky I am to have access to all this research, as well as the training to understand it.

As medical professionals, we cannot afford to be paternalistic and trust that people will follow advice without all the facts. This is especially true in Australia, where the vast majority of us have never witnessed firsthand the ravages that this disease can inflict.

Like all new converts, I am now a true believer: I’d like everyone to be vaccinated. But autonomy is a precious tenet of a free society, and I’m glad the ethicists have advised against mandating the vaccine

just hope that with more robust discussion and the wider dissemination of scientific knowledge, we may sway people like me — who have what may be valid reservations — to get the vaccine.

“It’s the anxiety, the frustration, the difficulty people have in scheduling appointments — which we are making with a very limited supply of vaccine that comes in — in quantities that we don’t know until it arrives,”

At least 28 states and Washington, D.C., have begun vaccinating older people, a New York Times survey shows, in many cases marking a shift in earlier plans that had put medical workers and nursing home residents at the front of the line for Covid-19 inoculations.

Other states have decided to remain focused exclusively on vaccinating health care workers and nursing home residents before opening up to a wider swath of the public.

Life will return to normal only when society as a whole gains enough protection against the coronavirus. Once countries authorize a vaccine, they’ll only be able to vaccinate a few percent of their citizens at most in the first couple months.

Tens of thousands of people have already received the vaccines, and none of them have reported any serious health problems.

“I couldn’t hug her,” Ms. Johnson said. “We didn’t share food. We each brought our own sandwich. It was just surreal.”

Alaska became the first state to make vaccinations available to all adults over the age of 16 earlier this month, followed by Mississippi. Several others have since followed suit, including Arizona, Utah, Indiana, Georgia and West Virginia.

Other states are moving to make more groups eligible ahead of schedule, based on age or underlying conditions.

According to a map released by the White House COVID-19 Response Team on Friday, four states have yet to confirm plans to expand eligibility ahead of the May 1 deadline: New York, Wyoming, Arkansas and South Carolina, where officials have said they are not on track to hit that threshold until May 3.

Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, said at the briefing that the country has seen an uptick in case counts and hospital admissions, with the most recent 7-day averages showing about 57,000 cases and 4,700 hospitalizations per day, and hospitalizations hovering around 1,000.

The U.S. is administering 2.5 million shots a day at its current pace, Zients said, adding that vaccine makers are "setting and hitting targets." Some 27 million doses went to states, tribes and territories this week.

Johnson & Johnson has accelerated production of its single-shot vaccine and is on track to deliver 11 million doses next week.

patients will not be able to choose which of the two vaccines they get.

the one produced by Bharat Biotech is being deployed prematurely. It still has yet to clear phase three clinical trials, and efficacy data isn't expected until March

Bharat Biotech's founder & chairman, Krishna Ella, told a Jan. 4 news conference his company's vaccine is "200% safe."

But there's a difference between giving an experimental drug to someone who is already sick, and giving a vaccine to someone who is healthy, says public health activist Dinesh Thakur.

Making vaccines — or least, mass-producing them — is something India is actually famous for. It's the world's largest vaccine producer, nicknamed 'the pharmacy to the world.'

She and others emphasized the apparent lack of severe health repercussions from reinfection — and the lack of evidence that reinfection is common.

Nearly 4 percent of people who had a previous infection were reinfected, an almost identical rate to those with no history of infection.

“Basically, it’s saying vaccination actually needs to be better than natural immunity. But vaccination is better than natural immunity.”

The study backs up recent laboratory data from South African researchers analyzing blood plasma from recovered patients. Nearly half of the plasma samples had no detectable ability to block the variant from infecting cells in a laboratory dish

The good news is that vaccine trials from Johnson & Johnson and Novavax show that vaccines can work — even against the B.1.351 variant, and particularly in preventing severe illness.

Novavax did not provide a breakdown of mild, moderate and severe cases, but severe cases of covid-19 were rare in the trial, suggesting that reinfection is unlikely to send people to the hospital.

“It is not surprising to see reinfection in individuals who are convalescent. And it would not be surprising to see infection in people who are vaccinated, especially a few months out from vaccine,”

“The key is not whether people get reinfected, it’s whether they get sick enough to be hospitalized.

“If the data holds true, it means we will need to walk the public back on the idea of how close we are to the finish line for ending this pandemic.”

Projections created by data scientist Youyang Gu — whose pandemic models have been cited by the Centers for Disease Control and Prevention — suggest that about 65 percent of America’s population will reach immunity by June 1. But built into that 65 percent is roughly 20 percent having immunity from past infections only.

In a separate study, scientists at Rockefeller University in New York took blood plasma from people who had been vaccinated and found that vaccine-generated antibodies were largely able to block mutations found on the B.1.351 variant.

I think the fact that we … now have data from two vaccines indicating that we can prevent serious disease, even against the new variant, is hopeful,”

A future concern needing close monitoring is whether the reformulation of vaccines to keep up with the evolving virus could drive the virus to continue evolving.

There is also a concern that subpar immunity could allow new resistant variants to emerge. That possibility, Nussenzweig said, is one reason that people should get both doses of a vaccine, on time.

“Usually by four to six weeks, there’s not much left,” said Deepta Bhattacharya, an immunologist at the University of Arizona. But germinal centers stimulated by the mRNA vaccines are “still going, months into it, and not a lot of decline in most people.”

The broader the range and the longer these cells have to practice, the more likely they are to be able to thwart variants of the virus that may emerge.

“Everyone always focuses on the virus evolving — this is showing that the B cells are doing the same thing,” said Marion Pepper, an immunologist at the University of Washington in Seattle. “And it’s going to be protective against ongoing evolution of the virus, which is really encouraging.”

Dr. Ellebedy’s team found that 15 weeks after the first dose of vaccine, the germinal center was still highly active in all 14 of the participants, and that the number of memory cells that recognized the coronavirus had not declined.

“The fact that the reactions continued for almost four months after vaccination — that’s a very, very good sign,” Dr. Ellebedy said. Germinal centers typically peak one to two weeks after immunization, and then wane.

After an infection or a vaccination, a specialized structure called the germinal center forms in lymph nodes. This structure is an elite school of sorts for B cells — a boot camp where they become increasingly sophisticated and learn to recognize a diverse set of viral genetic sequences.

The results suggest that a vast majority of vaccinated people will be protected over the long term — at least, against the existing coronavirus variants

But older adults, people with weak immune systems and those who take drugs that suppress immunity may need boosters; people who survived Covid-19 and were later immunized may never need them at all.

In the absence of variants that sidestep immunity, in theory immunity could last a lifetime, experts said. But the virus is clearly evolving.

“Anything that would actually require a booster would be variant-based, not based on waning of immunity,” Dr. Bhattacharya said. “I just don’t see that happening.”

The good news: A booster vaccine will probably have the same effect as prior infection in immunized people, Dr. Ellebedy said. “If you give them another chance to engage, they will have a massive response,” he said, referring to memory B cells.

Dr. Ellebedy said the results also suggested that these signs of persistent immune reaction might be caused by mRNA vaccines alone, as opposed to those made by more traditional means, like Johnson & Johnson’s

But that is an unfair comparison, because the Johnson & Johnson vaccine is given as a single dose, Dr. Iwasaki said: “If the J & J had a booster, maybe it will induce this same kind of response.”

He said only those who have had the disease understand how he feels. He had to get his hand on a vaccine quickly. But most of Tijuana's limited supply was going to front-line hospital workers.

He insists that no one at the vaccination site checked whether he worked or resided in the county, the two requirements necessary to get a shot there.

But vaccine tourism has become a bit of a phenomenon in Mexico. It's easy to find testimonies and tips on social media and in chat groups about getting a vaccine in the U.S.

The Biden administration has said the United States will send Mexico more than 2 million COVID-19 vaccine doses.

Earlier this month, President Biden said, "We're going to start off making sure Americans are taken care of first and then we're going to help the rest of the world."

"In this particular case, amid a worldwide pandemic, life and health of everyone should be priority No. 1,"

The country will also need to open more vaccination sites, some of which should be open 24/7 to ensure people who get off work at odd hours have easy access to the vaccine.“This is a wartime sort of response,” Fagbuyi said. “You’re going to pull all the stops and not leave any stone unturned.”

“Enjoy the opportunity, but also be cautious and look at what’s going on around you,” Fagbuyi said.

So, when will we get to a point where it won’t be so complicated for the general public to score a vaccine appointment? Fagbuyi predicts sometime in June.

Adalja predicts that by the Fourth of July, vulnerable people will be vaccinated in all states and there will no longer be concerns about reaching hospital capacity.

“We’re going to be trying to convince people to come get vaccinated,” Adalja said.

We often hear doctors say we want 70% of the population to be immune to COVID-19, whether through vaccination, natural infection or preexisting immunity, to achieve herd immunity. Each dose pricked in someone’s arm makes it harder for the virus to spread.

“What I think is more important than herd immunity is making sure vulnerable populations are vaccinated so that COVID loses the ability to cause severe illness, hospitalization and death,” Adalja said.

The trial’s first participants, a pair of 9-year-old twin girls, were immunized at Duke University in North Carolina on Wednesday.

Immunizing children will help schools to reopen as well as help to end the pandemic, said Dr. Emily Erbelding, an infectious diseases physician at the National Institutes of Health who oversees testing of Covid-19 vaccines in special populations.

An estimated 80 percent of the population may need to be vaccinated for the United States to reach herd immunity, the threshold at which the coronavirus runs out of people to infect.

“we were encouraged by the data from the 12 to 15 group,

Scientists will test three doses of the Pfizer vaccine — 10, 20 and 30 micrograms — in 144 children. Each dose will be assessed first in children 5 through 11 years of age, then in children ages 2 through 4 years, and finally in the youngest group, six months to 2 years.

After determining the most effective dose, the company will test the vaccine in 4,500 children

“It sounds like a good plan, and it’s exciting that another Covid-19 vaccine is moving forward with trials in children,”

Children represent 13 percent of all reported cases in the United States.

More than 3.3 million children have tested positive for the virus, at least 13,000 have been hospitalized and at least 260 have died

“We don’t know what the long-term effects of Covid infection are going to be,” Dr. Maldonado said.

Other vaccines have helped to control many horrific childhood diseases that can cause long-term complications, she added: “For some of us who’ve seen that, we don’t want to go back to those days.”

“So there’s a higher degree of confidence now in giving this vaccine to kids.”

“The more transparent you can be, the better.”

“I heard a lot from friends in Miami about people flying in, because they were giving it to everybody,”

, it began to seem like anyone could get a vaccine if they were willing to hunt one down or stretch the truth about their medical history.

“the equivalent of knocking over an old lady for a taxi and feeling good about yourself,” as she put it in an interview.

“It’s broadcasting status, that you got the vaccine ahead of others,”

“We should all consider taking up the Garbo challenge and stay off social media for a spell instead of broadcasting every waking second of the day, including your vax shot.”

Those people seemed just fine when they were splashing in bikinis in Turks and Caicos at Christmas,

Occasionally, those posting on Instagram have said that they were trying to say to others that the vaccine is safe and effective

“On some level, they know it’s tone-deaf for a wide audience but have their group where they feel safe,”

“What’s funny is that many of them just post their vaccination selfies to green circle Close Friends.”

“I mean, come on. You’re not Joe Biden. You’re not the queen,”

Three psychiatrists interviewed for this article said their patients all seemed to understand that attention deficit disorder and mild anxiety do not meet the state definition of an “intellectual” or “developmental” disorder sufficient to place them in the Centers for Disease Control and Prevention’s

“I have patients who brought stacks of medical info when they went to get vaccinated. No one ever asks to see it.”

“I’ve never had so many people happy to be told they’re obese,”

“At this point, the goal is to get as many people vaccinated as possible,”

He sees no issue with giving a note to a patient who had a melanoma five years back. Cancer is cancer. Elevated blood pressure is fine too, even if it’s sometimes less a reason than an excuse.

“Young people are the super-spreaders!

Some young people get around the fauxmorbidity issue by volunteering at a vaccine site.

. “It was basically treated as a given when I got there,”

“I get that people are eager to shame those who are gaming the system,” she said, “but let’s shame the people who set up that system.”

He points out that if one HIV vaccine had succeeded, the company behind it would have won big. Instead, all of the competitors in the vaccine field learned from collective failure and contributed to collective wisdom. The many false starts of HIV vaccination sired an explosion of new technologies and helped usher in a possible new golden age of vaccines.

We can call our record-breaking vaccine-development process good luck. Or we can call it what it really is: a ringing endorsement for the essential role of science in the world.

As a parable of scientific progress, I sometimes imagine the life cycle of a tree. Basic scientific research plants a variety of seeds. Some of these seeds fail entirely; the research goes nowhere. Some seeds become tiny shrubs; the research doesn’t fail entirely, but it produces little of value

And some seeds blossom into towering trees with abundant fruit that scientists, companies, and technologists pluck and turn into the products that change our lives. For years, mRNA technology looked like a shrub. In 2020, it blossomed in full view.

how can the public trust the right decisions were made

how can the public trust the right decisions were made

How can knowledgeable independent healthcare professionals endorse those decisions when they are not privy to the process?

Pfizer vaccine to have a 90% short term efficacy, and a single dose of the Oxford vaccine to have a 70% short term efficacy.

Would confidence in the vaccine be reduced by multiple reports of vaccine failures among at-risk individuals

Perhaps the UK could consider instead other ways to conserve vaccine supplies that may be safer than the delayed second dose option.

Also, for people who have recovered from Covid-19 a single vaccine dose may indeed be sufficient to boost their antibodies to high levels