The 2024–2025 season was the first in which every flu vaccine used in the United States was trivalent — built to protect against three flu viruses rather than four. The reason: B/Yamagata viruses had not circulated since March 2020, so trivalent and quadrivalent vaccines were expected to give similar protection against the viruses they cover, and trivalent vaccines are approved in many countries. A yearly flu vaccine remains the best way to prevent flu and its potentially serious complications.
What was in the vaccine
Each vaccine covered an A(H1N1) virus, an A(H3N2) virus and a B/Victoria virus. The H3N2 component was updated for the season in both kinds of vaccine.
| Egg-based vaccines | Cell- or recombinant-based vaccines | |
|---|---|---|
| H1N1 | A/Victoria/4897/2022 (H1N1)pdm09-like | A/Wisconsin/67/2022 (H1N1)pdm09-like |
| H3N2 (updated) | A/Thailand/8/2022 (H3N2)-like | A/Massachusetts/18/2022 (H3N2)-like |
| B/Victoria | B/Austria/1359417/2021-like | B/Austria/1359417/2021-like |
Supply
- Manufacturers projected as many as 148 million doses for the United States, a figure that could change during the season.
- Most of the supply was thimerosal-free or thimerosal-reduced (preservative-free); only multi-dose vials contained thimerosal.
FluMist at home — approved, but not yet
On September 20, 2024, the FDA approved the nasal spray vaccine FluMist for self- or caregiver administration. FluMist, which contains weakened live flu viruses, is approved for ages 2 through 49 and covers the same three virus types as other flu vaccines. During 2024–2025 it could still be given only by a health care provider, including at pharmacies; self-administration was not expected until the 2025–2026 season. Once available, people aged 18–49 could give it to themselves, and a caregiver 18 or older could give it to a child aged 2–17.
Paying for it
- Insured adults: most plans cover the annual flu shot as preventive care, at no cost — check that the provider takes your insurance. If a plan doesn't cover it or caps vaccine spending, there may be free or low-cost options.
- Uninsured adults: vaccines are often available free or cheaply at health providers, pharmacies, HRSA-supported health centers, employers, schools and community organisations, and can be found through Vaccines.gov.
- Children: most plans cover them at no cost. CDC's Vaccines for Children (VFC) program also provides free vaccine to children through age 18 who are American Indian or Alaska Native, Medicaid-eligible, uninsured or underinsured. Ask whether your child's doctor is a VFC provider, or ask your health department. An office visit or administration fee may still be charged.
Flu plus something else
It is possible to be sick with more than one respiratory virus at once — flu and COVID-19 together, or influenza A and B at the same time.
Sources
Based on "2024–2025 Flu Season," Centers for Disease Control and Prevention; a work of the United States government in the public domain.
Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
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