Composition of Vaccine
The composition of the U.S. flu vaccines are reviewed annually and updated as needed to match circulating flu viruses. Flu vaccines protect against three or four viruses (depending on the vaccine) that research suggests will be most common that season.
| Egg-Based Vaccines | Cell Culture-Based and Recombinant Vaccines |
| A/Victoria/4897/2022 (H1N1)pdm09-like Virus | A/Wisconsin/67/2022 (H1N1)pdm09-like Virus |
| A/Darwin/9/2021 (H3N2)-like Virus | A/Darwin/6/2021 (H3N2)-like Virus |
| B/Austria/1359417/2021 (Victoria lineage)-like virus | B/Austria/1359417/2021 (Victoria lineage)-like virus |
| B/Phuket/3073/2013 (Yamagata lineage)-like virus | B/Phuket/3073/2013 (Yamagata lineage)-like virus |
Egg Allergies
- All persons aged ≥6 months with egg allergy should receive influenza vaccine. Any influenza vaccine (egg based or nonegg based) that is otherwise appropriate for the recipient’s age and health status can be used.
- It is no longer recommended that persons who have had an allergic reaction to egg involving symptoms other than urticaria should be vaccinated in an inpatient or outpatient medical setting supervised by a health care provider who is able to recognize and manage severe allergic reactions if an egg-based vaccine is used
- Egg allergy alone necessitates no additional safety measures for influenza vaccination (beyond those recommended for any recipient of any vaccine, regardless of severity of previous reaction to egg)
- All vaccines should be administered in settings which personnel and equipment needed for rapid recognition and treatment of acute hypersensitivity reactions are available
Timing
For most persons who need only 1 dose of influenza vaccine for the season, vaccination should ideally be offered during September or October. Vaccination can continue after October and throughout influenza season as long as influenza viruses are circulating and unexpired vaccine is available.
Administration
- Quadrivalent inactivated influenza vaccine (IIV4) and recombinant vaccine (RIV4) can be administered simultaneously or sequentially with other inactivated vaccines or live vaccines and should be given at separate anatomic sites
- COVID-19 vaccines administered at the same time as influenza vaccines might be more likely to be associated with local injection site reactions. High Dose-IIV4 and adjuvanted influenza vaccine (aIIV4), and should be given in different limbs, if possible.
- Data is forthcoming and/or limited for more recently introduced vaccines (e.g., RSV). Providers should consult with current CDC/ACIP recommendations