Last year’s winter flu season was so severe that some doctors are recommending earlier flu shots this year. Like now.

The trouble with that advice?

“It’s absolutely wrong,” said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

While increasing the vaccination rate is a good idea, health officials say, at least 10 studies have found that the flu vaccine wears off as the weeks go by. Kaiser Permanente Northern California reported this month that the risk of a flu infection increases 15 percent every 28 days after vaccination.

The standard flu season peaks in mid-December and remains widespread through February. A shot in September might not yield any protection come February.

Delaying the start of vaccinations until late October would put pressure on clinics and flu shot providers, which prefer to spread patient visits over more days.

Osterholm said that shouldn’t matter. “We have to adjust the practice of medicine to the science of medicine,” he said, “and the science of medicine right now says get your flu shot as late as possible before the flu season.”

Ideally, patients should still get their shots before the start of flu season because it takes the body two weeks to produce flu-fighting antibodies triggered by the vaccine.

The federal Advisory Committee on Immunization Practices has adjusted its guidance on flu shot timing. Before the 2015-2016 season, the committee recommended shots as soon as a vaccine was available and “by October, if possible.” Now the committee recommends that shots be offered “by the end of October.”

Osterholm said the current flu vaccine remains a critical weapon to counter seasonal influenza, at least until research produces a “universal or game-changing vaccine” that provides improved — or even lifetime — immunity with a single dose.

U.S. Sen. Amy Klobuchar, D-Minn., recently co-authored a bill to increase funding for a new vaccine. Osterholm said such a funding increase is needed to produce a universal vaccine in the next decade.

Preliminary data from the Centers for Disease Control and Prevention show last year’s vaccine was 36 percent effective. The high mark in the past 15 flu seasons was the 2010-2011 vaccine, which was 60 percent effective.