What is the recommended flu vaccination protocol for adults?

Flu Vaccination Recommendation for Adults

All adults aged ≥6 months should receive annual influenza vaccination, with no exceptions based on health status or risk factors. 1

Universal Annual Vaccination

• Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. 1
• This universal recommendation has been in place since 2010, replacing the previous risk-based approach that targeted only high-risk groups. 2, 3
• Annual vaccination is necessary because immunity declines within the year following vaccination, and vaccine composition changes annually to match circulating strains. 1

Age-Specific Vaccine Selection

Adults Aged 18-64 Years

• Any age-appropriate influenza vaccine (inactivated influenza vaccine [IIV3], recombinant influenza vaccine [RIV3], or live attenuated influenza vaccine [LAIV3]) can be used. 1
• No preferential recommendation exists among vaccine types for this age group, except for solid organ transplant recipients (see below). 1

Adults Aged ≥65 Years

• Adults aged ≥65 years should preferentially receive one of three higher-dose or adjuvanted vaccines: high-dose inactivated influenza vaccine (HD-IIV3), recombinant influenza vaccine (RIV3), or adjuvanted inactivated influenza vaccine (aIIV3). 1
• If none of these three preferred vaccines is available at the time of vaccination, any other age-appropriate influenza vaccine should be used rather than delaying vaccination. 1
• This preferential recommendation for older adults is based on evidence showing improved protection with these enhanced formulations in this age group. 1

Special Populations

Solid Organ Transplant Recipients

• Adults aged 18-64 years who are solid organ transplant recipients receiving immunosuppressive medication regimens may receive either HD-IIV3 or aIIV3 as acceptable options (without preference over other age-appropriate IIV3s or RIV3). 1

Pregnant Women

• Influenza vaccination is recommended for all pregnant women during any trimester of pregnancy. 2
• Only inactivated influenza vaccines should be used; LAIV is contraindicated during pregnancy. 1

Healthcare Workers and Close Contacts

• Healthcare personnel and household members of high-risk persons should be vaccinated to reduce transmission to vulnerable populations. 1
• Healthcare workers caring for severely immunocompromised persons should receive IIV rather than LAIV. 1

Contraindications and Precautions

LAIV Contraindications

• LAIV should not be given to adults who:
  • Are pregnant 1
  • Have immunocompromising conditions, including HIV infection 1
  • Have anatomic or functional asplenia 1
  • Are close contacts or caregivers of severely immunocompromised persons 1
  • Have received influenza antiviral medications in the previous 48 hours 1
  • Have cerebrospinal fluid leak or cochlear implant 1

General Precautions

• Adults with a history of Guillain-Barré syndrome within 6 weeks of a previous influenza vaccine dose generally should not receive influenza vaccine. 1
• Persons with egg allergy who experience only hives can receive any age-appropriate vaccine (IIV, RIV, or LAIV). 1

Administration Details

• Vaccines should be administered intramuscularly in the deltoid muscle for adults. 1
• Only one dose is required annually for adults; a second dose does not improve antibody response in previously vaccinated adults. 1
• Vaccination should begin as soon as vaccine is available and continue throughout the influenza season as long as influenza viruses are circulating. 1

2024-25 Vaccine Composition

• All 2024-25 U.S. influenza vaccines are trivalent formulations (no longer containing influenza B/Yamagata component) with:
  • Influenza A/Victoria/4897/2022 (H1N1)pdm09-like virus (egg-based) or A/Wisconsin/67/2022 (H1N1)pdm09-like virus (cell/recombinant) 1
  • Influenza A/Thailand/8/2022 (H3N2)-like virus (egg-based) or A/Massachusetts/18/2022 (H3N2)-like virus (cell/recombinant) 1
  • Influenza B/Austria/1359417/2021 (Victoria lineage)-like virus 1

Clinical Impact

Influenza vaccination in elderly community-dwelling adults reduces pneumonia and influenza hospitalizations by 51%, all respiratory condition hospitalizations by 33%, and all-cause mortality by 45%. 4 Even when vaccine effectiveness against laboratory-confirmed illness is reduced (as can occur with H3N2 predominant seasons), vaccination still prevents serious outcomes including hospitalization, ICU admission, and death. 5