Flu season in the United States occurs throughout the fall and winter. While influenza viruses travel all year, flu activity often peaks between December and February. Still, it can linger as late as May.
For most people, September and October are favorable months to get vaccinated against the flu. Ideally, you should receive your vaccine by the end of October. Extra concerns on vaccine scheduling should be taken for particular groups of people.
Most adults 65 and older and pregnant women in their first or second trimester should avoid being vaccinated early (in July or August). Protection may wane over time and not last all the way through flu season. However, early vaccination should be considered for anyone unable to return at a later date to get vaccinated.
Some young adults and teens need two flu vaccination doses. It is suggested that those young adults receive the first dosage as soon as the vaccine becomes available. The second dose must be administered at least four weeks following the first. Vaccination throughout July and August is also an option for young adults and teenagers who only require one dose.