In the Northern Hemisphere, the best (and most common) time to be vaccinated is between September and December, ready for the winter months. The peak period for flu transmission is from late December to the end of March.
Ideally, you would want to be vaccinated and allow an additional 14 days to develop peak antibody protection, before coming into any contact with the flu virus. This is much easier to do at a time when the number of flu cases is low. Flu is highly contagious: the more community transmission that there is, the harder it becomes to avoid infection.
If you wait until there is a flu epidemic in progress, there may be not enough time for protection to kick in before you are exposed.
Another important consideration is that outbreaks tend to occur only after the “vaccination season” is over, by which time vaccine stocks have mostly been used up or are in very short supply, at which point it may not be possible to be vaccinated.
We advise early vaccination each season for peace of mind and maximum protection.