Sept. and Oct. are generally good times to be vaccinated against influenza. Ideally, everyone should be vaccinated by the end of October. Most adults, especially those 65 years and older, should generally not get vaccinated early (in July or August) because protection may decrease over time. Flu season starts in Oct. and continues until March of the following year. 

Influenza is a respiratory infection that can cause serious complications, particularly to young children, older adults and people with certain medical conditions. According to a U.S. Centers for Disease Control & Prevention (CDC) study, more than 200,000 people in the United States are hospitalized each year for respiratory and heart conditions, illnesses associated with influenza virus infections. 

“It takes about two weeks after vaccination for antibodies to develop in the body and provide protection against influenza virus infection. That's why it's best to get vaccinated before influenza viruses start to spread in your community,” says Dr. Carl Bryce, MD, Family Medicine Residency Program, Abrazo Central Campus.

The CDC also states receiving a flu shot offers the greatest protection against the flu, and annual vaccinations are recommended for all individuals six months or older who do not have specific medical conditions that would be exacerbated by the vaccine.  

“Flu vaccines cannot cause flu illness. Flu vaccines given with a needle (i.e., flu shots) are made with either inactivated (killed) viruses, or with only a single protein from an influenza virus. The nasal spray vaccine contains live viruses that are attenuated (weakened) so that they will not cause illness,” says Dr. Bryce, in response to those worried about the shot causing the illness.