Eighty-five days shy of October, the month when respiratory virus season typically begins in the U.S., the CDC and FDA have already made several key announcements about what clinicians can expect for the 2024-2025 round of vaccines for the infections that dominate during this time of year: influenza, respiratory syncytial virus and COVID-19.
Below are the most recent recommendations for the upcoming round of vaccines:
Flu
The 2024-2025 flu vaccines are recommended by the CDC for everyone 6 months of age and older. This year, the flu vaccine will likely transition back to a trivalent composition, removing the B/Yamagata lineage virus as a component.
"Influenza B viruses are classified into two lineages: B/Yamagata and B/Victoria," a March FDA committee recommendation reads. "However, the evidence indicates that the B/Yamagata lineage virus no longer poses a public health threat."
The recommendation was made by the FDA committee following discussion about the need for continuing the vaccine's quadrivalent formulation, which was used beginning in 2013-2014 until the most recent flu season 2023-2024.
For 35 seasons, the flu vaccine was trivalent. Reverting to the formulation is "strongly" recommended by the FDA for the 2024-2025 season. The committee suggested the trivalent vaccine target the following three strains:
- A/Victoria/4897/2022 (H1N1)pdm09-like virus
- A/Thailand/8/2022 (H3N2)-like virus
- B/Austria/1359417/2021 (B/Victoria lineage)-like virus
Relatedly, in light of recent and growing concerns over bird flu, the HHS awarded Moderna $176 million to develop mRNA-based pandemic influenza vaccines. The company noted its immediate focus would be on "late-stage development for an mRNA-based vaccine to enable the licensure of a pre-pandemic vaccine against H5 influenza virus," but it will also be tasked with developing other influenza vaccine candidates under the awards' terms.
RSV
Vaccination against RSV is now recommended for all adults over age 75 and high-risk adults between ages 60 and 74, the CDC announced June 26. The change was made to prioritize individuals most at risk of severe illness from the virus and "to simplify RSV vaccine decision-making for clinicians and the public," the agency stated.
Since the RSV vaccine is a single dose and not needed annually, the change is only intended to inform individuals over 75 who have not already received it, according to the CDC.
The agency still recommends that pregnant individuals receive a single dose of Pfizer's Abrysvo between weeks 32 through 36 of pregnancy during the fall respiratory season.
COVID-19
For the upcoming 2024-2025 COVID-19 vaccine, the FDA has told manufacturers to develop it using the KP.2 strain for the formula.
The KP.2 variant is part of the JN.1 lineage, but the specification to use the KP.2 strain resulted from current data, which shows that the current COVID-19 strains in circulation are more closely related to it.
"This change is intended to ensure that the COVID-19 vaccines (2024-2025 Formula) more closely match circulating SARS-CoV-2 strains," the FDA wrote in its update. "The agency does not anticipate that a change to KP.2 will delay the availability of the vaccines for the United States."
As of June 27, the CDC recommended everyone 6 months or older receive the updated COVID-19 shot this fall.