Everyone, except infants younger than 6 months, is recommended to get the flu shot as soon as it comes out in the market, typically around October. Early vaccination provides the best protection against seasonal flu, states vaccines.gov.
It is essential to avail of the flu shot on an annual basis, since flu seasons generally vary. In the United States, the onset of the flu season may occur in early October and continue until late May, notes the United States Centers for Disease Control and Prevention.
Within this span of time, the number of flu-related cases reaches its highest mark between December and February. Although early immunization remains the most effective countermeasure against the flu, people can still get the flu shot in January and derive protection from the vaccine.