The CDC’s Advisory Committee on Immunization Practices (ACIP) issued its updated recommendations for the use of seasonal influenza vaccines for the 2021-22 influenza season. ACIP continues to recommend routine annual influenza vaccination for all persons aged ≥6 months who do not have contraindications. The 2021-22 influenza season will coincide with the continued circulation of SARS-CoV-2, the virus that causes COVID-19. Influenza vaccination of persons aged ≥6 months to reduce the prevalence of influenza illness will lead to fewer patients presenting with symptoms that might be confused with COVID-19 symptoms. Prevention of and reduction in the severity of influenza illness and reduction of outpatient visits, hospitalizations, and intensive care unit admissions through influenza vaccination could also alleviate stress on the US healthcare system, the committee notes. (Additional guidance is available for vaccine planning during the pandemic, on the use of COVID-19 vaccines, and for clinical guidance).
TYPES AND COMPOSITION OF INFLUENZA VACCINES
During the 2021-22 influenza season, the following types of vaccines are expected to be available. All are quadrivalent.
- Inactivated influenza vaccines (IIV4s)
- Recombinant influenza vaccine (RIV4)
- Live, attenuated influenza vaccine (LAIV4)
The composition of the 2021-22 US influenza vaccines includes updates to the influenza A(H1N1)pdm09 and influenza A(H3N2) components. US-licensed influenza vaccines will contain hemagglutinin derived from an influenza A/Victoria/2570/2019 (H1N1)pdm09-like virus (for egg-based vaccines) or an influenza A/Wisconsin/588/2019 (H1N1)pdm09-like virus (for cell culture-based and recombinant vaccines), an influenza A/Cambodia/e0826360/2020 (H3N2)-like virus, an influenza B/Washington/02/2019 (Victoria lineage)-like virus, and an influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus.
2021-22 UPDATES
The approved age indication for the cell culture-based inactivated influenza vaccine, Flucelvax Quadrivalent (ccIIV4), has been expanded from ages ≥4 years to ages ≥2 years.
Discussion of administration of influenza vaccines with other vaccines includes considerations for coadministration of influenza vaccines and COVID-19 vaccines. Vaccines that are given at the same time should be administered in separate anatomic sites. Providers should consult current ACIP COVID-19 vaccine recommendations and CDC guidance concerning coadministration of these vaccines with influenza vaccines.
Vaccination Timing
As previously recommended, children who need two doses (children ages 6 months through 8 years who have never received influenza vaccine or who have not previously received a lifetime total of two or more doses) should receive their first dose as soon as possible after vaccine becomes available to allow the second dose (which must be administered ≥4 weeks later) to be received by the end of October.
Guidance concerning timing of influenza vaccination now states that vaccination soon after vaccine becomes available can be considered for pregnant women in the third trimester.
Early vaccination (July, August) should be avoided in nonpregnant adults unless there is concern that later vaccination might not be possible. Among older adults, data suggest that early vaccination (in July and August) might be associated with waning immunity before the end of influenza season. However, while delaying vaccination might result in greater immunity later in the season, deferral might also result in missed opportunities to vaccinate, as well as challenges in vaccinating a population within a shorter time period. The relative effects of other determinants of the impact of vaccination (such as timing and severity of influenza season) also contribute to uncertainty regarding the optimal timing of vaccination. ACIP recommendations cite a recent study that used mathematical modeling to assess various scenarios of vaccination timing, timing of onset of the influenza season, rate of waning, and vaccine effectiveness, and found that, with a historical average timing of onset of the influenza season, delaying vaccination until October resulted in more hospitalizations if >11% of persons aged ≥65 years who would have been vaccinated in August or September failed to get vaccinated. No recommendation is made for revaccination (ie, providing a booster dose) later in the season of persons who have already been fully vaccinated.
For all adults, efforts should be structured to optimize vaccination coverage before influenza activity in the community begins. Vaccination should continue to be offered throughout the influenza season, as long as unexpired vaccine is available, since influenza activity can begin in February or March in some communities. To avoid missed opportunities for vaccination, providers should offer vaccination during routine healthcare visits and hospitalizations when vaccine is available.
Contraindications/Precautions
Contraindications and precautions to the use of ccIIV4 and RIV4 have been modified, specifically with regard to persons with a history of severe allergic reaction (egg, anaphylaxis) to an influenza vaccine. A history of severe allergic reactions to a previous dose of any egg-based IIV, LAIV, or RIV of any valency is a precaution to use of RIV4. Use of ccIIV4 and RIV4 in such instances should occur in an inpatient or outpatient healthcare setting under supervision of a provider who can recognize and manage a severe reaction. For ccIIV4, history of a severe allergic reaction to any ccIIV of any valency or any component of ccIIV4 is a contraindication to future use of ccIIV4. For RIV4, history of a severe allergic reaction to any RIV of any valency or any component of RIV4 is a contraindication to future use of RIV4.
SARS-CoV-2
During the 2021-22 influenza season, it is expected that SARS-CoV-2 will continue to circulate in the United States, and COVID-19 vaccinations are expected to continue. Current guidance for the administration of COVID-19 vaccines indicate that these vaccines can be administered with other vaccines, including influenza vaccines.
Considerations for Specific Populations
The updated 2021-22 influenza recommendations repeat many of the CDC’s previous recommendations on most topics related to influenza vaccination in specific populations. Key points from this section of the CDC’s recommendations are highlighted here; see the full document at the CDC’s website for detailed information on all of these topics.
Vaccination is particularly important for persons who are at increased risk for severe complications from influenza and for influenza-related outpatient, emergency department, or hospital visits, as well as persons who live with or care for persons at higher risk for influenza-related complications. Continued emphasis should be placed on the vaccination of persons who live with or care for persons at higher risk for influenza-related complications (see Table).
Table. Persons at Higher Risk for Medical Complications Attributable to Severe Influenza
- All children aged 6 through 59 months
- All persons aged ≥50 years
- Adults and children who have chronic pulmonary (including asthma), cardiovascular (excluding isolated hypertension), renal, hepatic, neurologic, hematologic, or metabolic disorders (including diabetes mellitus)
- Persons who are immunocompromised due to any cause (including but not limited to immunosuppression caused by medications or HIV infection)
- Women who are or will be pregnant during the influenza season
- Children and adolescents (6 months of age through 18 years) who are receiving aspirin- or salicylate-containing medications and who might be at risk for experiencing Reye syndrome after influenza virus infection
- Residents of nursing homes and other long-term care facilities
- American Indians/Alaska Natives
- Persons who are extremely obese (body mass index ≥40 for adults)
An IIV4 or RIV4, as appropriate for the recipient’s age, is suitable for persons in all risk groups. LAIV4 is not recommended for some populations, including some of these listed groups, as discussed in the CDC’s update.
More information on influenza is available on the CDC website.
