When you get your flu shot matters

Every year, there is controversy involving the flu vaccine. How effective is it? Should you get it? But a new study aims to address another question: When is the best time to get the shot?

An analysis from the University of Pittsburgh School of Medicine found that tens of thousands of flu cases and hundreds of deaths might be avoided if older adults wait until October to get the vaccine instead of when it first comes out in August. The results were published in the April issue of the American Journal of Preventive Medicine.

However, the authors noted there might be consequences to getting vaccinated later if the season arrives earlier than usual or people decide to skip the shot.

A previous study from 2017 found that protection from the vaccine wanes as the season progresses. Those who wait until it is closer to the start of flu season have greater immunity. But if only one in every 20 people who normally get the shot choose to skip it, all the gains would be negated, the study found.

“What we’ve found is that it’s a balancing act, but if a clinician believes a patient will return for vaccination in the fall, then our analysis shows that it is best if they advise that patient to wait," said lead author Kenneth J. Smith, professor of medicine in Pitt’s Division of General Internal Medicine.

Researchers focused on adults older than 65 years, who tend to have higher early vaccination rates and weaker immune systems than younger adults. They ran computer models using data from the 2013-14 and 2014-15 flu seasons to forecast the number of cases, hospitalizations, and deaths, and compared a later vaccination schedule with an earlier vaccination schedule to see how things would play out when flu seasons peaked in December, February, or April.

For the normal (February) and late (April) peaks in flu season, the projection models showed that getting the vaccine later may save as many as 258 lives and prevent about 22,000 cases of flu. But if the flu peaked early (December), which it tends to do one in every four seasons, the models predicted dozens of adults would die because they were not vaccinated in time.

But if more than 5.5 percent of older adults who normally get the shot skip it because of the later vaccination schedule, it would not prevent as many flu cases as just letting people get the shot on their current schedule, researchers found.

“In all scenarios, simply getting vaccinated is the best way to avoid the flu,” said Smith. “If the choice is between getting the influenza immunization early or not getting it at all, getting it early is definitely better.”

Currently, rates of flu are still elevated throughout the country. As of March 2, there have been 64 pediatric deaths for the 2018-19 season, the Centers for Disease Control and Prevention reported. (Adult deaths are not tracked nationally until later.)

As of March 9, flu was considered widespread throughout Pennsylvania with the highest levels in the northwest and southeast regions. There have been a total of 62,501 cases this year with 75 adult deaths associated with the flu. One child has died from the flu, according to the state’s Department of Health.

In New Jersey, flu activity is reported to be high throughout the state. There have been 11,303 cases reported so far for the season. Three children have died from the flu, according to the state’s Department of Health.