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Respiratory Viruses

This guide covers viral respiratory infections, including influenza, RSV, and other influenza-like illnesses (ILI)

Influenza Vaccines ("Flu Shot")

Different Types of Flu Vaccines
Quadrivalent Influenza Vaccine

The standard "flu shot" is a unadjuvanted quadrivalent vaccine that protects against four (4) different flu viruses, licensed for people over 6 months. This vaccines are manufactured from virus grown in eggs. Individuals who are allergic to eggs/egg products should not use this vaccine.

High Dose Quadrivalent Influenza Vaccine

A standard quadrivalent vaccine with a higher antigen dose to create a stronger immune response, it's licensed for people over 65.

Live Attenuated Influenza Vaccine (LAIV)

In intranasal (nasal spray) vaccine authorized for people ages 2 to 49. This live attenuated influenza vaccine should NOT be given to people who are pregnant or immunocompromised.

Adjuvanted Flu Vaccine

A quadrivalent vaccine with an added ingredient (MF59) to create a stronger immune response, approved for people over 65.

Cell-Based Flu Vaccine

A vaccine manufactured from viruses grown in cell culture, this vaccine is egg-free and is approved for people over 6 months.

Recombinant Influenza Vaccine

An egg-free vaccine for people over 18.

SourceCDC: Flu Vaccines

2023-2024 Flu Vaccine

Flu Vaccine Recommendations for the 2023-2024 season

A couple of things are different for the 2023-2024 influenza (flu) season:

  • The composition of flu vaccines has been updated. Flu vaccines for the U.S. 2023-2024 season will contain the following:
    Egg-based vaccines
      • an A/Victoria/4897/2022 (H1N1)pdm09-like virus; (Updated)
      • an A/Darwin/9/2021 (H3N2)-like virus;
      • a B/Austria/1359417/2021 (B/Victoria lineage)-like virus; and
      • a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.
  • Cell- or recombinant-based vaccines
      • an A/Wisconsin/67/2022 (H1N1)pdm09-like virus; (Updated)
      • an A/Darwin/6/2021 (H3N2)-like virus;
      • a B/Austria/1359417/2021 (B/Victoria lineage)-like virus; and
      • a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.
      • These recommendations include one update compared to the 2022-2023 U.S. flu vaccine composition. The influenza A(H1N1)pdm09 vaccine virus component was updated for egg-based and cell- or recombinant-based flu vaccines.

Updated Information for Individuals with Egg Allergies

People with egg allergy may get any vaccine (egg-based or non-egg-based) that is otherwise appropriate for their age and health status.

Previously, it was recommended that people with severe allergy to egg (those who have had any symptom other than hives with egg exposure) be vaccinated in an inpatient or outpatient medical setting.

Beginning with the 2023-2024 season, additional safety measures are no longer recommended for flu vaccination of people with an egg allergy beyond those recommended for receipt of any vaccine, regardless of the severity of previous reaction to egg. All vaccines should be given in settings where allergic reactions can be recognized and treated quickly.

Projected U.S. Flu Vaccine Supply for the 2023-2024 Season
  • Vaccine manufacturers have projected that they will supply the United States with as many as 156.2 million to 170 million doses of influenza vaccines for the 2023-2024 season. These projections may change as the season progresses.
    • All flu vaccines for the 2023-2024 season will be quadrivalent (four-component).
    • Most will be thimerosal-free or thimerosal-reduced vaccines (91%), and about 21% of flu vaccines will be egg-free.
  • The latest information on total distribution of influenza vaccine doses for the 2023-2024 season is available.