This fall and winter the flu virus and the virus that causes COVID-19 may both be spreading. Vaccination is the best defense against both COVID-19 and the flu. Flu Statistics Facts About Influenza And Flu Season 2020 Sep 13 2021. . Getting vaccinated in late May or early June should provide good levels of protection during the peak of the influenza season and may even last through to November by which time the influenza season has usually finished. September and October are considered the best months to receive the flu vaccine. While roll-out for the COVID-19 vaccine was staggered in order to vaccinate the most vulnerable first no such plans are in place for the flu vaccine roll-out at present. With the potential for influenza to extend into the spring its never too late to get vaccinated. The highest level of protection occurs in the first 3 to 4 months following vaccination. Current recommendations which. ...