Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2022–23 Influenza Season

Introduction

Influenza viruses typically circulate annually in the United States, most commonly from the late fall through the early spring. Most persons who become ill after influenza virus infection recover without serious complications or sequelae. However, influenza can be associated with serious illnesses, hospitalizations, and deaths, particularly among older adults, very young children, pregnant persons, and persons of all ages with certain chronic medical conditions (1–7). Influenza also is an important cause of missed work and school (8–10). Routine annual influenza vaccination for all persons aged ≥6 months who do not have contraindications has been recommended by CDC and the Advisory Committee on Immunization Practices (ACIP) since 2010 (11).

Vaccination provides important protection from influenza illness and its potential complications. The effectiveness of influenza vaccination varies depending on several factors, such as the age and health of the recipient; the type of vaccine administered; the types, subtypes (for influenza A), and lineages (for influenza B) of circulating influenza viruses; and the degree of similarity between circulating viruses and those included in the vaccine (12). During each of the six influenza seasons from 2010–11 through 2015–16, influenza vaccination prevented an estimated 1.6–6.7 million illnesses, 790,000–3.1 million outpatient medical visits, 39,000–87,000 hospitalizations, and 3,000–10,000 respiratory and circulatory deaths each season in the United States (13). During the severe 2017–18 season, notable for an unusually long duration of widespread high influenza activity throughout the United States and higher rates of outpatient visits and hospitalizations compared with recent seasons, vaccination prevented an estimated 7.1 million illnesses, 3.7 million medical visits, 109,000 hospitalizations, and 8,000 deaths (14), despite an overall estimated vaccine effectiveness of 38% (62% against influenza A[H1N1]pdm09 viruses, 22% against influenza A[H3N2] viruses, and 50% against influenza B viruses) (14).

Influenza circulated at historically low levels in the United States and globally during the 2020–21 influenza season (15). This was coincident with widespread implementation of nonpharmaceutical interventions (e.g., masking, social distancing, and suspension of in-person work and school) intended to prevent transmission of SARS-CoV-2 (the virus that causes COVID-19). Influenza activity increased during the 2021–22 season, although severity indicators (e.g., influenza-associated hospitalizations and deaths) were overall lower than in recent previous seasons (16). Timing, intensity, and severity of the 2022–23 influenza season cannot be predicted. Influenza vaccination remains an important tool for the prevention of potentially severe respiratory illness, which might decrease stress on the U.S. health care system during ongoing circulation of SARS-CoV-2. Guidance for vaccine planning during the COVID-19 pandemic is available at https://www.cdc.gov/vaccines/pandemic-guidance/index.html.

This report updates the 2021–22 ACIP recommendations regarding the use of seasonal influenza vaccines (17) and provides recommendations and guidance for vaccination providers regarding the use of influenza vaccines in the United States for the 2022–23 season. Various formulations of influenza vaccines are available (Table 1). Contraindications and precautions for the use of influenza vaccines are summarized (Tables 2 and 3). Abbreviations are used in this report to denote the various types of vaccines (Box).

This report focuses on recommendations and guidance for the use of seasonal influenza vaccines for the prevention and control of influenza during the 2022–23 season in the United States. A summary of these recommendations and a Background Document containing additional information on influenza, influenza-associated illness, and influenza vaccines are available at https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html.

Methods

ACIP provides annual recommendations for the use of influenza vaccines for the prevention and control of seasonal influenza in the United States. The ACIP Influenza Work Group meets by teleconference once to twice per month throughout the year. Work group membership includes several voting members of ACIP, representatives of ACIP liaison organizations, and consultants. Discussions include topics such as influenza surveillance, vaccine effectiveness and safety, vaccination coverage, program feasibility, cost effectiveness, and vaccine supply. Presentations are requested from invited experts, and published and unpublished data are discussed.

The Background Document that supplements this report is updated periodically to reflect recent additions to the literature related to recommendations made in previous seasons and minor changes in guidance for the use of influenza vaccines (e.g., guidance for timing of vaccination and other programmatic issues, guidance for dosage in specific populations, guidance for selection of vaccines for specific populations that are already recommended for vaccination, and changes that reflect use that is consistent with indications and prescribing information licensed by the Food and Drug Administration [FDA]). The summary included in the Background Document for such topics is not a systematic review; it is intended to provide an overview of current literature, with updated articles being identified primarily through a broad search for English-language articles on influenza and influenza vaccines. Typically, systematic review and evaluation of evidence using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach (18) are performed for new recommendations or substantial changes in the current recommendations (e.g., expansion of the recommendation for influenza vaccination to new populations not previously recommended for vaccination or potential preferential recommendations for specific vaccines). Systematic review, GRADE, and the ACIP Evidence to Recommendations Framework were used in the development of the updated recommendations for influenza vaccination of adults aged ≥65 years discussed in this document.

Primary updates and changes to the recommendations described in this report include 1) the vaccine virus composition for 2022–23 U.S. seasonal influenza vaccines; 2) updates to the description of influenza vaccines expected to be available for the 2022–23 season, including one influenza vaccine labeling change that occurred after the publication of the 2021–22 ACIP influenza recommendations; and 3) updates to the recommendations concerning vaccination of adults aged ≥65 years. Information relevant to these changes includes the following:

• Recommendations for the composition of Northern Hemisphere influenza vaccines are made by the World Health Organization (WHO), which organizes a consultation, usually in February of each year. Surveillance data are reviewed, and candidate vaccine viruses are discussed. Information about the WHO meeting on February 25, 2022, for selection of the 2022–23 Northern Hemisphere vaccine viruses is available at https://www.who.int/news/item/25-02-2022-recommendations-announced-for-influenza-vaccine-composition-for-the-2022-2023-northern-hemisphere-influenza-season. Subsequently, FDA, which has regulatory authority over vaccines in the United States, convenes a meeting of its Vaccines and Related Biological Products Advisory Committee (VRBPAC). This committee considers the recommendations of WHO, reviews and discusses similar data, and makes a final decision regarding vaccine virus composition of influenza vaccines licensed and marketed in the United States. Materials from the VRBPAC discussion on March 3, 2022, during which the composition of the 2022–23 U.S. influenza vaccines was discussed, are available at https://www.fda.gov/advisory-committees/advisory-committee-calendar/vaccines-and-related-biological-products-advisory-committee-march-3-2022-meeting-announcement.
• Regarding recommendations concerning newly licensed influenza vaccines and changes to the licensed indications for existing vaccines, ACIP relies on FDA for review of safety, immunogenicity, and efficacy and effectiveness data pertaining to licensure and labeling of influenza vaccines. Vaccines that are expected to be available for the 2022–23 season are described (see Vaccines Available for the 2022–23 Season) (Table 1). Regulatory information pertinent to the change in age indication for Flucelvax Quadrivalent discussed in this report is available at https://www.fda.gov/vaccines-blood-biologics/vaccines/flucelvax-quadrivalent.
• Regarding updated recommendations for influenza vaccines for adults aged ≥65 years, a summary of the review of evidence on this topic is available at https://www.cdc.gov/vaccines/acip/recs/grade/influenza-older-adults.html. A summary of the ACIP Evidence to Recommendations Framework for this discussion is available at https://www.cdc.gov/vaccines/acip/recs/grade/influenza-older-adults-etr.html .

Primary Changes and Updates

Routine annual influenza vaccination of all persons aged ≥6 months who do not have contraindications continues to be recommended. Primary updates in this report include the following:

1. The composition of the 2022–23 U.S. seasonal influenza vaccines includes updates to the influenza A(H3N2) and influenza B/Victoria components. For the 2022–23 season, U.S.-licensed influenza vaccines will contain hemagglutinin (HA) 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/Darwin/9/2021 (H3N2)-like virus (for egg-based vaccines) or an influenza A/Darwin/6/2021 (H3N2)-like virus (for cell culture–based or recombinant vaccines); an influenza B/Austria/1359417/2021 (Victoria lineage)-like virus; and an influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus.
2. Influenza vaccines expected to be available for the 2022–23 season, their age indications, and their presentations are described (Table 1). Afluria Quadrivalent is not expected to be available in a 0.25-mL prefilled syringe presentation. When using Afluria Quadrivalent for children aged 6 through 35 months (who require a 0.25-mL dose), the dose must be obtained from a multidose vial. One labeling change is described. In October 2021, FDA granted approval for the use of Flucelvax Quadrivalent (cell culture–based quadrivalent inactivated influenza vaccine [ccIIV4]) for children aged 6 months through <2 years. As of March 2021, Flucelvax Quadrivalent had been approved for persons aged ≥2 years. Approval for children aged 6 months through <2 years was based on results of a randomized, observer-blind study that compared immunogenicity and safety of Flucelvax Quadrivalent with that of a licensed comparator IIV4 among 2,402 children aged 6 through 47 months, of whom 894 were aged 6 through 23 months. Flucelvax Quadrivalent is now approved for persons aged ≥6 months.
3. On the basis of review of evidence concerning high-dose inactivated influenza vaccine (HD-IIV), recombinant influenza vaccine (RIV), and MF59-adjuvanted inactivated influenza vaccine (aIIV), recommendations for influenza vaccination of persons aged ≥65 years have been modified. ACIP recommends that adults aged ≥65 years preferentially receive any one of the following higher dose or adjuvanted influenza vaccines: quadrivalent high-dose inactivated influenza vaccine (HD-IIV4), quadrivalent recombinant influenza vaccine (RIV4), or quadrivalent adjuvanted inactivated influenza vaccine (aIIV4). If none of these three vaccines is available at an opportunity for vaccine administration, then any other age-appropriate influenza vaccine should be used. Higher dose vaccines include HD-IIV4 and RIV4, both of which contain a higher dose of HA antigen per virus than standard-dose vaccines (60 µg for HD-IIV4 and 45 µg for RIV4, compared with 15 µg for standard-dose inactivated vaccines). Adjuvanted inactivated influenza vaccine (aIIV4) contains MF59 adjuvant.

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Créditos: Comité científico Covid