A new vaccine recently approved by FDA to protect against respiratory syncytial virus (RSV) means Americans will have three vaccines available to them — flu, COVID-19, and RSV — to prevent a "tripledemic" of respiratory illnesses in the winter. But experts are concerned vaccine uptake may be challenging.

Can the US avoid a tripledemic?

Last year, the flu may have led to as many as 58,000 deaths, according to CDC, while COVID-19 claimed around 50,000 lives between November and March, and RSV kills up to 10,000 people each year. Only vaccines for the flu and COVID-19 were available last year, but two new vaccines, made by Pfizer and GlaxoSmithKline (GSK), have received FDA approval and CDC recommendation for Americans ages 60 and older.

The three vaccines are a "godsend" for older and immunocompromised Americans, according to Ofer Levy, director of the prevision vaccines program at Boston Children's Hospital and an advisor to FDA.

"The number of elders who die of viral infection every winter in our intensive care units, and also sometimes in the summer, is large — it's in the tens of thousands of individuals," he said. "Each of these vaccines is a huge win."

However, it's unclear just how many Americans will take the vaccines. Around 71% of adults ages 65 and older got a flu shot last winter, and around 43% got a COVID-19 booster.

Levy said bundling all three vaccines into one clinical visit is likely to encourage more people to get immunized. "Plus, you want to get these shots in arms before the viral respiratory season in the winter," he said.

But experts expressed concern about this approach for multiple reasons. For one, vaccines can sometimes work against each other if administered at the same time, the New York Times reports.

Camille Kotton, an infectious diseases physician at Massachusetts General Hospital said she's "clinically concerned" about how taking the flu and RSV shots simultaneously could affect antibody response. "I would say, when possible, it might be good to spread them out," she added.

Experts also expressed concern over the safety of the new RSV vaccines. Neither Pfizer nor GSK enrolled enough people who were immunocompromised, medically frail, live in a long-term care facility, or 75 or older to determine how effective their RSV vaccines were in those groups, which are those most vulnerable to the disease.

Pfizer and GSK also reported three neurological cases within 42 days of vaccination in a population of around 40,000 people, though the trials weren't able to determine whether those cases were caused by the vaccines.

"That information really can't be obtained until post licensure and post recommendation and rollout," said Helen Chu, a physician and immunologist at the University of Washington.

The chance of adverse events related to the RSV vaccines made some advisors to CDC reluctant to recommend them for people who don't face a high risk of infection, which is partly why the panel said anyone ages 60 or older "may" decide to get the shot in consultation with a doctor.

However, Chu noted that recommendation will place a burden on general physicians and other healthcare providers. "It's hard for the committee," she said. "It's certainly going to be much, much harder for a G.P."

Regardless, Levy emphasized the three shots could still be lifesavers this winter. "We never have all the information we want," he said. "But one thing we know for sure is that every winter people lose loved ones, grandmothers, grandfathers to the viruses, and now we have better tools. And we want to deploy them." (Mandavilli, New York Times, 7/5; Moreno, Axios, 7/6)