Advisory Committee on Immunization Practices Makes Recommendations for the 2020–21 Influenza Season

A report by Grohskopf, et al. (2020) in today's MMWR updates the 2019–20 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines in the United States (MMWR Recomm Rep 2019;68[No. RR-3]). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. For each recipient, a licensed and age-appropriate vaccine should be used. Inactivated influenza vaccines (IIVs), recombinant influenza vaccine (RIV4), and live attenuated influenza vaccine (LAIV4) are expected to be available. Most influenza vaccines available for the 2020–21 season will be quadrivalent, with the exception of MF59-adjuvanted IIV, which is expected to be available in both quadrivalent and trivalent formulations.

The CDC and ACIP recommend yearly flu vaccination for all people 6 months of age and older. This season inactivated influenza vaccines, recombinant influenza vaccines, and live attenuated influenza vaccines are expected to be available. New for the 2020-21 flu season, two new flu vaccines have been licensed for use in people aged 65 years and older: a quadrivalent (4-component) high-dose flu vaccine and a quadrivalent adjuvanted flu vaccine. Both vaccines are intended to produce a better immune response in people 65 years of age and older, and, therefore, better protection. Previously, high-dose and adjuvanted flu vaccines were only available in trivalent formulations. There is no preferential recommendation for one flu vaccine over another for people for whom more than one licensed, recommended and appropriate vaccine is available.

As the authors explain, "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. However, vaccination provides important protection from influenza illness and its potential complications. During 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. During the recent 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)."

Enter COVID-19. As the authors observe, "In late 2019, a novel coronavirus, SARS-CoV-2, emerged as a cause of severe respiratory illness. In March 2020, the World Health Organization (WHO) declared coronavirus disease 2019 (COVID-19) a global pandemic. The common signs and symptoms of COVID-19 (e.g., fever, cough, and dyspnea) can also occur with influenza illness. As of August 2020, SARS-CoV-2 continues to circulate and cause severe illness in the United States and worldwide. The extent to which SARS-CoV-2 will circulate over the course of the 2020–21 influenza season is unknown. However, during the continued or recurrent circulation of SARS-CoV-2 concurrently with influenza viruses during the upcoming fall and winter, influenza vaccination of persons aged ≥6 months can reduce prevalence of illness caused by influenza, and can also reduce symptoms that might be confused with those of COVID-19. Prevention of and reduction in the severity of influenza illness and reduction of outpatient illnesses, hospitalizations, and intensive care unit admissions through influenza vaccination also could alleviate
stress on the U.S. healthcare system."

Regarding composition of the 2020-21 influenze vaccines, the authors explain, "All influenza vaccines licensed in the United States will contain components derived from influenza viruses antigenically similar to those recommended by FDA (https://www.fda.gov/advisory-committees/advisory-committeecalendar/vaccines-and-related-biological-products-advisorycommittee-march-4-2020-meeting-announcement). Most influenza vaccines available in the United States for the 2020–21 season will be quadrivalent vaccines, with the exception of MF59-adjuvanted IIV (aIIV), which is expected to be available in both trivalent (aIIV3, Fluad) and quadrivalent
(aIIV4, Fluad Quadrivalent) formulations."

For the 2020–21 season, U.S. egg-based influenza vaccines (i.e., vaccines other than ccIIV4 and RIV4) will contain HA derived from:
• an influenza A/Guangdong-Maonan/SWL1536/2019
(H1N1)pdm09-like virus;
• an influenza A/Hong Kong/2671/2019 (H3N2)-like virus;
• an influenza B/Washington/02/2019 (Victoria lineage)-
like virus; and
• for quadrivalent vaccines only, an influenza B/
Phuket/3073/2013 (Yamagata lineage)-like virus.

For the 2020–21 season, U.S. cell culture–based inactivated (ccIIV4) and recombinant (RIV4) influenza vaccines will contain HA derived from:
• an influenza A/Hawaii/70/2019 (H1N1)pdm09-like
virus;
• an influenza A/Hong Kong/45/2019 (H3N2)-like virus;
• an influenza B/Washington/02/2019 (Victoria lineage)-
like virus; and
• an influenza B/Phuket/3073/2013 (Yamagata lineage)-
like virus.
The 2020–21 composition reflects updates in the
influenza A(H1N1)pdm09, influenza A(H3N2), and
influenza B (Victoria lineage) components.

Guidance for vaccine planning during the pandemic is available at https://www.cdc.gov/vaccines/pandemic-guidance/index.html

Reference: Grohskopf LA, et al. Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2020–21 Influenza Season. MMWR. Vol. 69, No. 8. Aug. 21, 2020.

Source: CDC

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