Vaccination, Flu Shot

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PITTSBURGH — Tens of thousands of flu cases and hundreds of deaths could be avoided if older adults waited until October to get their flu shot, an eye-opening new study concludes.

Researchers at the University of Pittsburgh’s School of Medicine analyzed the outbreaks of influenza cases in the United States over a two-year period to determine the best time for the public to get their flu shots. They found that getting immunized when the vaccine is offered may not be best after all.

The flu vaccine’s effectiveness dissipates over time as the season progresses, previous research has shown. Waiting until the start of flu season to get the vaccination provides better immunity. If flu season arrives early, however, or if more than one in 20 individuals miss their shot, the gains are often offset, according to the most recent study.

“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,” says lead author Dr. Kenneth J. Smith, professor of medicine and clinical and translational science, in a university release. “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.”

The researchers used data from the 2013-14 and 2014-15 flu seasons. They forecast the number of total cases, hospitalizations, and deaths if flu seasons peaked in December, February, or April. The researchers defined “peak” as the period that had the largest number of flu cases.

By using “compressed” vaccination distribution, which begins in October instead of August, as is the standard for people over 65, the researchers projected 258 lives saved and 22,062 more cases of the flu prevented. The researchers say seniors are particularly at risk when the vaccine’s effectiveness begins to weaken.

That said, should flu season peak early, which happens every four years on average, then hundreds of older adults would die because they didn’t get the flu shot on time.

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

The study is published in the American Journal of Preventive Medicine.

About Ben Renner

Writer, editor, curator, and social media manager based in Denver, Colorado. View my writing at

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