The 2023-2024 respiratory season was moderate, and this season is likely to be about the same, infectious disease experts said. Updated vaccines for COVID-19 and influenza are now available and ideally should be administered in September or October.
The CDC expects the upcoming fall and winter respiratory disease season to have a similar or lower number of peak hospitalizations from COVID-19, influenza and respiratory syncytial virus (RSV) compared with last season, according to the agency’s 2024-2025 Respiratory Disease Season Outlook. However, the emergence of a new COVID-19 variant or influenza subtype with more severe outcomes, or low vaccine uptake, could alter the outcomes, they warned.
Last season, more than 10% of the U.S. population had the flu, and at the peak of the respiratory season, more than 2,500 people per week died from COVID-19, said Jeff Nesbit, the assistant secretary for public affairs at the Department of Health and Human Services, in an August press briefing.
Uptake of flu vaccines last year was “not quite as good as it has been in the past,” William Schaffner, MD, a professor of preventive medicine at Vanderbilt University School of Medicine, in Nashville, Tenn., told Infectious Disease Special Edition.
“We were recovering still from the pandemic, but there was a lot of vaccine fatigue,” Dr. Schaffner said. “Last year was very unusual because we were recommending for the first time for most people two vaccines—influenza and the updated COVID vaccine—and for people ages 60 and older, there was the new RSV vaccine on the scene. So it was a distinctive season. … We’re obviously hoping not only to recover but do much better this year.”
Still, flu vaccines last year were estimated by the CDC to reduce the risk for flu medical visits by two-thirds and flu-related hospitalizations by about half for vaccinated children, and flu medical visits by half and hospitalizations by about 40% for vaccinated adults.
Both the flu and COVID-19 vaccines have been updated for the new season. Flu vaccines will now be trivalent instead of quadrivalent, including an influenza A (H1N1), an A (H3N2) and a B/Victoria-lineage vaccine virus. Because influenza B/Yamagata viruses included previously are no longer actively circulating, their inclusion in flu vaccines is no longer warranted, according to the CDC.
So far, the updated COVID-19 vaccine closely matches the KP.3 family of viruses that continue to grow in dominance, CDC Director Mandy Cohen, MD, MPH, said in an August press briefing. The CDC estimates that the effectiveness of the seasonal flu vaccine against hospitalization will likely range from 33% to 50%, and that effectiveness of RSV vaccination against hospitalization will range from 73% to 88%, the outlook report noted. RSV vaccines are 70% effective in preventing older adults from being hospitalized and 90% effective at preventing hospitalizations in babies, Dr. Cohen said.
Respiratory season in the Southern Hemisphere was moderate this year, a good indicator that the season here could be similar, said Stuart C. Ray, MD, FACP, FIDSA, a professor of medicine at the Johns Hopkins University School of Medicine, in Baltimore.
“The [flu] strains circulating have not surprised the experts, … so I think that we should be in pretty good shape going into the season,” said Dr. Ray, who is also a member of the editorial advisory committee of Infectious Disease Special Edition. “I think the biggest challenge we face is encouraging people to receive the vaccine because it will reduce their risk of getting sick by about half.”
Here are the CDC recommendations for this season:
- Everyone 6 months or older should receive the updated 2024-2025 COVID-19 and influenza vaccines, including pregnant people.
- Infants younger than 8 months and children 8 months to 19 months with risk factors should receive passive immunization with nirsevimab (Beyfortus, Sanofi/AstraZeneca), typically October through March.
- A maternal RSV vaccine (Abrysvo, Pfizer) is recommended for pregnant people between 32 and 36 weeks’ gestation and typically given September through January.
- Adults older than 75; adults 60-74 with risk factors such as heart disease, obesity and diabetes; and older adults residing in nursing homes should get an RSV vaccine (Abrysvo; Arexvy, GSK; or mResvia, Moderna). The RSV vaccine affords longer protection, so these recommendations are for people who did not get an RSV vaccine last year, Dr. Cohen said. RSV has been circulating in nursing homes, she added.
Flu and COVID-19 vaccines can be given simultaneously, Dr. Schaffner said: “Some people like to spread them out, but a vaccine deferred, I’m afraid, is often a vaccine never received, because somehow we get too busy to come back for that next dose.”
For people who are vaccine-averse, vaccines “aren’t our only means of protection,” Dr. Ray added. “High-quality masks, like respirators, work very well when worn properly, and they work for all of these viruses.”
Drs. Ray and Schaffner reported no relevant financial disclosures.
This article is from the October 2024 print issue.