Delaying Flu Shot May Benefit Older Adults

July 31st, 2019

Flu shots typically become available in August, but waiting until October to get vaccinated may be best for older adults, according to a research study from the University of Pittsburgh. Over time, the effectiveness of the flu vaccine in an individual declines and the risk of contracting the flu rises. Because flu season often increases in October and peaks between December and February, researchers suggest that getting vaccinated closer to the start of flu season may provide better protection.

Using data from the 2013-2014 and 2014-2015 flu seasons, the researchers ran computer models to forecast the number of cases, hospitalizations, and deaths in people aged 65 or older that would occur if the vaccination period began in August versus October and found that starting vaccinations later in the year could save as many as 258 lives and prevent up to 22,062 cases of flu. The study team focused on people aged 65 and up because they tend to receive flu shots earlier in the season and because decreased vaccine effectiveness is more of a threat to older adults whose immune systems are not typically as strong as younger people.

Although the results suggest that delaying the flu shot is beneficial, the authors point out that if flu season arrives early or if delayed vaccination prompts more than one in 20 people who would otherwise be vaccinated to skip their flu shot, then the gains are lost. According to lead author Kenneth J. Smith, MD, MS, “There’s controversy in the public health community over whether influenza vaccination should happen as soon as the vaccine becomes available in August, or if it’s better to wait until later in the fall,” but these study findings can help clinicians determine when to offer flu shots. For example, if patients have multiple appointments each year and will be in the office in the fall or if they are in a senior community where flu immunization is offered through a scheduled clinic, then waiting is likely advisable. But if a patient typically comes in only for an annual check-up and is unlikely to seek out the flu vaccine in the fall, getting vaccinated when convenient­—even if that is in August—is best.

Interested in participating in research studies related to this topic? Visit the Immune Systems & Infections page on the Pitt+Me website.