This Year's Flu Shot Is a 'Good Match,' CDC Says—But Cases and Hospitalizations Continue to Rise

This year’s influenza vaccine is “a very good match” to the strains currently circulating, Rochelle Walensky, MD, director of the Centers for Disease Control and Prevention (CDC), said in a press briefing on December 5.

The news of the flu vaccine’s efficacy comes in the midst of an unusually early and intense flu season that has sent tens of thousands of Americans to the hospital in recent weeks.

The disconnect between these two—namely, high levels of flu even with access to an effective vaccine—likely has a lot to do with people approaching this flu season differently. Vaccination rates are low, and more people are gathering while they’re sick, experts said.

“Using vaccines is the way that we can reduce disease burden,” Andrew Pekosz, PhD, a virologist at the Johns Hopkins Bloomberg School of Public Health, said in a press briefing. “Vaccines that sit on the shelf are of no use—it’s vaccines that are in people’s arms that actually mediate the reduction in disease potential.”

But with the flu season in full swing, how can people protect themselves and their loved ones, especially with the holidays coming up?

Here’s what experts had to say about why the flu vaccine should be able to prevent severe disease, why unvaccinated people may be especially susceptible to the flu this year, and what to do as the flu virus peaks over the next few weeks.

Availability of a Well-Matched Flu Vaccine

The flu virus, similar to the COVID virus, mutates and changes each year, which means that flu shots also have to be updated annually.

“It takes a long time to develop the vaccine, so at the end of the year they have to make their best guess as to what to include in the upcoming vaccine,” Emily Sickbert-Bennett, PhD, director of infection prevention at the University of North Carolina Medical Center, told Health. “Even though there is fluctuation year to year, [flu vaccines] are very effective at reducing severe disease and preventing deaths."

When the flu shot doesn’t match the flu strains that end up circulating, they’re considered less effective and not as well-matched—even still, these poorly-matched vaccines can lower a person’s risk of going to the hospital with the flu, Dr. Walensky said in a briefing.

But when flu shots do end up mirroring the virus strains that are circulating—as is the case with this year’s vaccine—getting the shot can reduce a person's risk of having to go to the doctor with flu by 40%–60%.

“We see 35% decreased rates of hospitalization even when we don’t have a good match, which really just emphasizes when we do have a good match, how much more effective it will be,” Dr. Walensky said. “We do know that if we do a lot of the work now and people roll up their sleeves to get vaccinated, there is a lot that we can do to prevent severe disease.”

Factors Keeping Flu Cases High, Even With a Good Vaccine 

Despite the flu vaccine being well-matched to the strains circulating this year, the CDC estimates that between 120,000 and 260,000 people were hospitalized with flu from October 1 to December 3. During the same period, there were between 6 million and 13 million flu-related medical visits.

The reason for this, experts explained, is that people are now more susceptible to the flu—for reasons both in and out of their control.

For one, flu vaccination rates are fairly low—as of October, 26% of adults had received a flu shot, and by late November about 42.5% of children were vaccinated.

There’s no magic number that experts are looking for in terms of vaccination, Sickbert-Bennett explained, but more vaccinations means less severe illness from the flu.

In addition to less vaccine-induced immunity, the lack of flu infections in 2020 and 2021 have also made this season worse.

“Virus infection always does cause an increase in your immunity that protects you from influenza for sometimes one or two more years,” Pekosz said. “And the lack of that virus-induced immunity is probably meaning that more of us are susceptible, particularly people who aren’t taking the vaccine.”

There’s also the matter of the flu shots themselves; even though they’re a good match, no vaccine is ever 100% effective, Pekosz explained.

But, while flu hospitalizations and case rates are high, it’s likely not because the virus itself is more severe.

“[The numbers] are high and they’re occurring early,” Pekosz said. “But if you think about them in proportion to the total number of cases, we’re not seeing a very strong increase in the percent of cases that are driving severe disease right now.”

How to Stay Healthy

With flu hospitalizations as high as they are, it’s important that people try to reduce transmission, especially ahead of the holiday season where more gatherings will be taking place.

“As hard as it was during COVID to cancel things, it still feels hard,” Sickbert-Bennett said. “Maybe even, I should say, because of COVID, it feels [harder] to cancel things because we’re so excited to do things now.”

The 2021-2022 flu season was much milder than this current season, and much milder than pre-pandemic flu seasons. But interestingly, adult flu vaccination rates in October of this year are actually about three percentage points higher than they were in October 2021.

Vaccination rates are just one piece of the puzzle, then—people are, in general, likely engaging in fewer preventative measures now that would otherwise stop viral spread, Sickbert-Bennett said.

All of these precautionary measures adopted during COVID can also be used to help prevent flu and RSV transmission, explained Keri Althoff, PhD, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health.

“Our vaccination rates are not where they need to be regarding the COVID bivalent booster and regarding the influenza vaccines, so we are going to need additional layers of mitigation strategies,” she said in a press briefing.

Hand washing, masking, moving holiday gatherings to well-ventilated areas, and taking a COVID test before seeing elderly relatives are all ways to help decrease transmission of flu, RSV, and COVID over the holidays, Althoff explained. Holiday gatherings often include family members of varying age groups, and since pregnant people, kids under 2, and adults over 65 are at the highest risk of getting severe complications from the flu, it’s best to make sure they don’t get sick.

“Thinking about, in particular, the most vulnerable people that are coming to your holiday gatherings and choosing your mitigation strategies appropriate to them is the way to go,” Althoff said.

Besides holiday gatherings, masking in public spaces—especially if a person is feeling under the weather—is also a good idea, Althoff added.

“People are going to have to make a lot of individual level decisions about thinking about who they're spending time with, what activities they have upcoming,” Sickbert-Bennett said. “I find myself happy to always have my mask available with me if I do happen to be around others that seem like they might be getting sick.”

In general, preventing flu transmission is all about listening to your body—a negative COVID test result shouldn’t be considered a clean bill of health if someone has influenza-like symptoms, such as fever, sore throat, and cough.

“If you’re feeling symptomatic and you test negative for COVID-19, usually the most likely reason is that you’re infected with something else,” Pekosz said. “If you’re feeling sick, there really should be no difference whether you’re testing positive for COVID-19, for flu, or for RSV—if you’re feeling sick, stay home.”

In addition to reducing flu transmission, the most important metric for now is making sure that hospitals don’t get overwhelmed with respiratory virus patients.

“The indicator that we’re closely watching right now is hospitalizations,” Althoff said. “And we all know from the last two years that when hospitals fill with sick patients and health care workers are also getting ill, this is not the ideal situation for individuals seeking care for respiratory illness or for other illnesses or injury.”

To that end, Althoff and Sickbert-Bennett encouraged eligible people who haven’t yet gotten their flu shot to do so as soon as possible. Even though flu cases are high currently, people haven’t missed their window of opportunity.

“It’s definitely not too late. We are in the thick of flu season and it’s hard to predict really how long it will last,” Sickbert-Bennett said. “It began for us in October and is staying at a really high level now into December. So I would say don’t hesitate to go ahead and get your flu vaccine, because now is a great time to be protected.”