Is it time to brace for a “tripledemic”—flu, COVID, and RSV?

Learn what to expect this season, and how this year is already different from any other.

close up of vaccination in arm

Updated on September 12, 2023.

Last year, flu season got underway much earlier than usual, marking its worst start in more than a decade. Meanwhile, a jump in new COVID cases and a worrisome spike in RSV infections resulted in what was dubbed a “tripledemic.”

So, what can we expect this year?

As always, vaccination rates go a long way in determining how cold and flu seasons play out. There are vaccines to protect against all three of these viruses. It’s the best way to protect yourself and others from getting sick or avoiding severe infections and related complications. But there are a few other ways experts can predict what’s to come. Here is what we know so far.

What Australia’s flu season means for U.S.

Australia had an early spike to its flu season this year. The number of confirmed cases by July was well above the country’s five-year average.  Why does this matter for the United States?

Flu season in the Southern Hemisphere starts in April and lasts until September, while it spans October to May in the Northern Hemisphere. So, flu season in Australia is ending just as it’s about to begin in the United States. U.S. health officials monitor what happens in the southern hemisphere to help predict what’s in store for the northern hemisphere. In other words, if Australia just had a bad flu season, chances are we’re next.

Another notable takeaway from Australia: the highest number of cases were among kids. Children accounted for nearly 80 percent of flu-related hospitalizations, according to The Commonwealth Scientific and Industrial Research Organization (CSIRO), an Australian Government agency.

Why were young children disproportionately affected? Australia experts say a stark drop in vaccination rates is the most likely explanation. Only about 23 percent of Australian kids younger than 5 were vaccinated this year, compared to about 41 percent in pre-pandemic years. This year roughly 13 percent of children ages 5 to 15 were vaccinated, compared to about 26 percent pre-COVID.

This reflects a broader, worrisome trend. COVID triggered “largest sustained decline in childhood vaccinations in approximately 30 years,” according to the World Health Organization (WHO) and UNICEF. Worldwide, some 25 million children are missing out on life-saving vaccines, and “the consequences will be measured in lives,” cautioned Catherine Russell, UNICEF Executive Director in a July 2022 news release.

Last year in the U.S., flu vaccination rates among children were about 55 percent, slightly lower than 2021 and about 7 percent lower than 2020 around the time the pandemic began, according to the Centers for Disease Control and Prevention (CDC). Meanwhile, about 47 percent of adults were vaccinated, a slight uptick from about 45 percent the year before.

How COVID and RSV may complicate flu season

Ongoing surveillance shows that as of August 26, COVID-related hospitalizations and deaths are back on the rise.

And just as flu season gets underway, there is a third virus to consider: RSV. Respiratory syncytial virus (RSV) also tends to spread in the fall and winter months. Anyone can get it and most kids are infected by the age of 2, but research suggests that COVID precautions in recent years contributed to an “immunity gap”— an increase in vulnerable new babies and reduced immunity from lack of exposure to the virus.

On September 5, the CDC issued a Health Alert Network (HAN) Health Advisory, notifying healthcare providers and caregivers about a recent increase in RSV activity in parts of the Southeastern United States, which suggests the rest of the country may see similar increases over the next couple of months.

Like flu, most people with RSV recover within a couple weeks. But for some people, these infections can be more serious and lead to complications—or even death.

The CDC estimates that since 2010, influenza has resulted in between 9 million and 41 million illnesses, between 140,000 and 710,000 hospitalizations and between 12,000 and 52,000 deaths each year.

Children and the elderly are especially vulnerable to RSV-related complications. Among children younger than 5 years old, the virus accounts for 58,000 to 80,000 hospitalizations in the U.S. every year. Among adults ages 65 and older, RSV leads to roughly 60,000 to 160,000 hospitalizations and between 6,000 and 10,000 deaths, according to the Centers for Disease Control and Prevention (CDC).

What vaccines to get—and when

The good news: There are vaccines to help protect against the flu, COVID—and now RSV.

Flu: The CDC recommends that nearly everyone aged 6-months or older receive a flu vaccine each year. September and October are the best months to get vaccinated against the flu. Ideally, everyone should get their shot by the end of October. But it’s never too late. That goes for children, too. Kids 6-months or older are eligible. In fact, Lynette Brammer, acting deputy chief for science for the Epidemiology and Prevention Branch (EPB) of CDC’s Influenza Division, says "very consistently year to year" about 80 percent of flu deaths among children involve kids who are not vaccinated.

And for people older than 65, high-dose flu vaccines are recommended. These high-dose shots can help older people develop a stronger immune response against the flu.

Don’t be deterred by the fact that the flu vaccine isn’t a perfect shield (its average efficacy is about 40 percent to 60 percent). The percentage of people who get the vaccine is far more important to public health than its efficacy. For example, a flu vaccine that’s only 20 percent effective could still save nearly 62,000 lives if 43 percent of the population got one, a 2018 study published in Proceedings of the National Academy of Sciences found. Boost that vaccination rate to 50 percent of the population, and nearly 8,500 additional flu deaths are avoided.

COVID: The U.S. Food and Drug Administration (FDA) approved an updated COVID booster on September 11. The latest shots will target a descendent of Omicron known as the XBB.1.5, which is closely related to the variants currently in circulation. Health officials advise that getting this latest booster will offer protection against COVID in the fall and winter months. The FDA says the following groups can receive an updated vaccine:

  • All people ages 5 and older (regardless of previous COVID vaccination) are eligible to receive a single dose of the updated Pfizer or Moderna COVID booster at least 2 months since their last dose of any COVID vaccine. 
  • Children ages 6 months to 4 years who are already vaccinated against COVID are eligible to receive one or two doses of the updated Pfizer or Moderna COVID booster. The timing and exact number of doses given depends on previous COVID vaccines. Talk to your children's healthcare provider about what is best for them.
  • Unvaccinated children ages 6 months to 4 years are eligible to receive three doses of the updated Pfizer COVID booster or two doses of the updated Moderna COVID booster.

The CDC approved the FDA's decision, recommending the updated COVID booster for everyone ages 6 months and older. “We have more tools than ever to prevent the worst outcomes from COVID-19,” said Director Mandy Cohen, MD, MPH in a September 12 news release. “CDC is now recommending updated COVID-19 vaccination for everyone 6 months and older to better protect you and your loved ones.” 

You can get your flu shot and a COVID booster at the same time. It’s both safe and effective. The CDC also says that side effects are about the same whether a vaccine is given alone or at the same time as other vaccines. Tip: If you tend to get a sore arm or muscle, you can receive your shots in different arms. If you get them in the same arm, the two injections should be spaced at least one inch apart.

RSV: The CDC recommends the use of nirsevimab—a monoclonal antibody that has been shown to reduce the risk of both hospitalizations and healthcare visits for RSV in infants by about 80 percent.

All infants younger than 8 months, born during or entering their first RSV season should receive one dose of nirsevimab. (Typically, RSV cases rise in October, peak in January or February and decline by April or May.) Children between 8 and 19-months old who are at increased risk of severe RSV, such as children with weakened immune systems, should get another dose in their second RSV season.

The FDA also recently approved a vaccine called Arexvy, which is made by GSK, for the prevention of lower respiratory tract disease caused by RSV in adults ages 60 and older. A similar vaccine developed by Pfizer called Abrysvo was also approved for older adults, and pregnant people to protect newborns during the first six months of life. The shot, which may be given between 32 and 36 weeks of pregnancy, is the first vaccine to protect infants from RSV.

For the upcoming RSV season, the CDC advises those age 60 or older who've been advised by their HCP to receive an RSV vaccine to not wait—and get their shot as soon as it becomes available in their area. This will help ensure they are protected before the virus begins circulating in their community, health officials explain. The CDC, however, has not yet recommended the Pfizer RSV vaccine for pregnant people.

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