You probably know you should get a flu shot. But do you know when you should get it?

The Centers for Disease Control and Prevention recommendation is for all adults and children at least six months old to take some form of the influenza vaccine (unless their physician believes there to be a contraindication, or reason not to). Most health care professionals will agree with that recommendation. But the timing of our flu shot can have an impact on its effectiveness.

“The key is that you don’t want people to get the vaccine too early, for example August or September, only to have the immunity wane in February or March when the attack rates can be high,” says Dr. George Kuchel, director of the UConn Center on Aging.

The vaccine’s effectiveness tends to not last as long in the elderly as it would in younger people.

“Also, you don’t want people to get the vaccine too late, for example December or January, only to be unprotected during those earlier months,” Kuchel says.

Just as it’s an educated guess each year as to which strains of the influenza virus the vaccine should target, it’s impossible to pinpoint when the flu season will start, how long it will last, and how severe it will be.

The sweet spot this year seems to be October and November. The CDC recommendation is by the end of October.

Dr. Montgomery Douglas, chair of the UConn Health Department of Family Medicine, sees patients of all ages. While he agrees with late October being the ideal time, early or late is still much better than not at all.

“The primary issue we have with the flu vaccine in both young and old is not enough people get it, period, not the timing of it per se,” Douglas says. “So once the vaccine becomes available, I start giving it whenever eligible persons are in the office, because chances are – like many in the U.S. – a big chunk of them otherwise might miss it entirely.”

Things to know about the flu shot:

• It takes about two weeks for the flu vaccine to take hold and be protective.
• Getting a flu shot cannot give you the flu. Some people can get mild symptoms in the first few days as their body develops antibodies.
• The flu vaccine comes in several varieties. Consult your doctor to determine which is best for you.
• Children who need two doses in the same flu season “should be vaccinated as soon as possible, as the second vaccine, which is needed for full protection, is administered at least four weeks after the initial dose,” says David Banach, infectious diseases physician and hospital epidemiologist. The CDC recommends children between ages 6 months and 8 years who are getting vaccinated for the first time get the booster.
• For health care professionals, caregivers, and expectant mothers, inoculation from the flu is especially important. It’s not just to protect yourself, it’s also to help keep others from getting sick.
• Flu season historically peaks between December and February in the United States, but it can vary by region.
• A flu shot doesn’t guarantee you won’t get the flu, but it is the best way to protect against infection and it can make the flu less severe if you do end up with it.

Learn more about family medicine at UConn Health at health.uconn.edu/family-medicine.

Learn more about infectious diseases at UConn Health at health.uconn.edu/infectious-diseases.

Learn more about the UConn Center on Aging at health.uconn.edu/aging.