Will the flu shot work and when should you take it?

When it comes to the upcoming influenza season, there’s a potential mismatch between the vaccine and what might circulate, raising the risk that the flu season could be severe. And that risk could be even higher because of low uptake of the influenza vaccine so far.

The Center for Infectious Disease Research & Policy (CIDRAP for short) at the University of Minnesota has been receiving reports that the dominant strain of flu this season in other parts of the world that get flu earlier — H3N2 subclade K — doesn’t match the new vaccine very well.

Pamela Gomez, respiratory disease epidemiologist in the Utah Department of Health and Human Services, said people should still be vaccinated against the flu. “As soon as possible is the best action,” she told Deseret News, as even a less-than-perfect match will help keep those who get the flu from hospitalization. It should still reduce the severity should one be sickened by influenza.

Gomez noted that it’s also impossible to say what will be circulating in the U.S. when flu season really kicks up in coming weeks.

So far, doctors in the U.S. say they’re mostly seeing H1N1, another influenza A that matches the vaccine. But what’s dominant could change, including the H3N2 subclade K, later as other factors like international travel and who’s exposed change.

The holidays — and in fact, winter itself — are key times for influenza and other respiratory illnesses to be passed around for a number of reasons. People gather together more indoors, Gomez said. She said it’s not uncommon to see more cases of such illnesses right after Thanksgiving, Christmas or other winter holidays because people come together during those, from extended family meals to special programs to celebrate. Gatherings and travel — think sitting with hundreds of strangers on public transportation — all raise the risk.

When should you be vaccinated?

Last month would have been dandy, but it’s not too late. Gomez said the prime time to get the most immunity is September and October, but right away at this point is better than not at all.

This could be the second severe flu season in a row, according to CNN. Last winter ushered in more flu hospitalizations than the country has seen in close to 15 years. And at least 280 children died of flu, which is the highest number since public health started gathering the data in 2004.

A word of warning

Researchers in Canada are emphasizing the vaccine-virus mismatch to encourage the U.S. and its residents to pay attention to flu, since the Centers for Disease Control and Prevention has been less active on flu than in the past.

“This is not the time to be flying blind into the respiratory virus season,” Dr. Danuta Skowronski, chief influenza and emerging respiratory pathogens epidemiologist at the British Columbia Centre for Disease Control, told CIDRAP News last week. The Canadian researchers published a paper on the vaccine-virus mismatch in the Journal of the Association of Medical Microbiology and Infectious Disease Canada.

Skowronski, one of the paper’s authors, said that Canada counts on what’s happening in the U.S. to help Canada prepare for its flu season, just as the U.S. pays attention to other parts of the world, especially the Southern Hemisphere, where flu season is typically May to July and offers a peek at what might be coming.

What goes into each year’s flu vaccine is a best guess by experts who watch what is circulating elsewhere. North America takes note of what’s happening in South America, since that flu season plays out first. But subclade K showed up late in the season, so it did not influence the makeup of the flu vaccine preparation for this year. The early indications from the United Kingdom and Japan indicate it’s going to be a prominent strain.

But it also is unlikely to be the only strain of flu going around. Vaccination remains helpful. In the UK, the current vaccine has been about 70%-75% effective in keeping children with flu from needing hospitalization. It’s been about 30%-40% effective in keeping adults out of the hospital.

U.S. public health officials say it’s still a guess what will circulate and dominate here. And Skowronski called the subclade K “a drift, not a shift,” which is clearly better. The subtype, she told CIDRAP, has been circulating in humans since 1968, changing along the way to stay viable against immune system attacks.

When vaccination rates lag

IQVIA, a health information and research company, has reported that in the U.S., retail pharmacies have administered at least 2 million fewer flu vaccines than in the past. The pharmacy numbers matter because that’s where close to two-thirds of flu vaccines are taken.

“I’m not surprised,” Dr. Jennifer Nuzzo, director of Brown University’s Pandemic Center, told CNN. She said that vaccine skepticism promoted even by some leaders at the U.S. Department of Health and Human Services has “injected chaos into the whole vaccination system,” she said.

In Australia, where vaccination has also fallen and subclade K is dominant, there have been more than 443,000 cases of flu, which is a national record, per the article.

U.S. case counts

The CDC reports that flu case counts are low, but climbing right now, up 2% for the week ending Nov. 8, which was the most recent report available. Most of the cases were influenza A(H3N2).

Richard Webby, who studies the flu at St. Jude Children’s Research Hospital in Memphis, told NPR that H3N2 viruses “tend to be a little bit more problematic. When we have an H3N2 season, we tend to have a little bit more activity, a little bit more disease at the severe end of the spectrum.”

The CDC report said 1,665 people were admitted to hospitals with flu this week, but mortality data was not available.

Tips for avoiding flu

Besides suggesting that people get vaccinated, Gomez offered some advice to help folks avoid the flu, regardless of which strain is circulating.

“Basic hygiene is underrated but one of the best ways to stay safe,” she said. That means washing your hands regularly, especially if you are out and about and shaking hands or touching things other people commonly touch, like door knobs and handrails. Those items, at home and elsewhere, should be disinfected regularly.

Anyone with symptoms of illness should stay home, and away from others as much as possible to help prevent spread.

Finally, she said to do healthy things like getting good sleep, eating nutritious food and exercising. Those all help one’s immune system.