A Combined Flu and COVID-19 Shot May Be Coming

As much as we’d like to think that COVID-19 is behind us, the virus isn’t going anywhere. Health officials continue to recommend that people get vaccinated for both COVID-19 and influenza every year for the foreseeable future, and high hospitalization rates for COVID-19 in the past winter were a reminder that SARS-CoV-2 can still cause serious disease.

Soon, that may be possible with one shot instead of two. On June 10, Moderna reported that its combination COVID-19/influenza shot generated even better immune responses against SARS-CoV-2 and influenza than those elicited by existing, separate vaccines.

Both of the shots used in the study are experimental. The COVID-19 portion relies on a slightly different form of SARS-CoV-2’s spike protein than the existing vaccine. Instead of encoding for the entire spike protein, the combination vaccine includes two key parts of it in a way that streamlines the shot to require a lower dose—which is useful for a combination vaccine, and also potentially extends its shelf life. The influenza component of the vaccine uses the same mRNA technology behind the existing COVID-19 vaccine but targets influenza proteins in the three strains that circulated during the past season: H1N1 and H3N2 from the influenza A group, and an influenza B strain.

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In a study of more than 8,000 adults ages 50 and older, about half received the combination vaccine. The other half—the control group—received two separate shots: Moderna's latest COVID-19 vaccine, which targets the XBB.1.5 variant, and a flu shot (either Fluarix, if people were 50 to 64 years old, or Fluzone HD for those 65 and older).

In the younger group, the combo vaccine generated about 20% to 40% higher levels of antibodies to the influenza strains, and 30% higher levels to XBB.1.5, compared to the control group. Among older people, antibodies were 6% to 15% higher against the flu strains and 64% higher against XBB.1.5 compared to older people in the control group.

“The real advantage of a single shot is that people only need to get one needle," says Dr. Jacqueline Miller, senior vice president and head of development in infectious diseases at Moderna. There's a public-health advantage, too, she says, since U.S. vaccination rates for both diseases are relatively low. "When we are able to give the two vaccines as one, it could increase vaccine compliance rates, especially for those at highest risk."

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Moderna is continuing to study the COVID-19 vaccine and the flu shot used in the combo as separate shots as well. That data will also help the U.S. Food and Drug Administration (FDA) when it reviews the company’s request for approval of the combination shot, which could come by the end of the year. The specific strains targeted in the shot will depend on which forms of the viruses are circulating at the time. (The company also filed a request to the FDA on June 7 to update its COVID-19 vaccine to target the JN.1 variant.)

The combination vaccine will likely not arrive in time for the flu and COVID-19 season this fall. But in coming years, a two-in-one vaccine could help to increase vaccination rates, which in turn could contribute to lower hospitalization rates for both diseases.