vaccination in December or even later is still beneficial because the virus that causes influenza circulates past the new year. The number of influenza cases usually peaks around February, but this peak can come earlier or later (ranging from December to May).

sharing of quality influenza surveillance and monitoring data by countries allows WHO to:

provide countries, areas and territories with information about influenza transmission in other parts of the world to allow national policy makers to better prepare for upcoming seasons; describe critical features of influenza epidemiology including risk groups, transmission characteristics, and impact; monitor global trends in influenza transmission; and support the selection of influenza strains for vaccine production.