The Advisory Committee on Immunization Practices (ACIP) has updated the 2018–19 recommendations regarding the use of seasonal influenza vaccines in the United States (MMWR Recomm Rep 2018;67[No. RR-3]). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. A licensed, recommended, and age-appropriate vaccine should be used. Inactivated influenza vaccines (IIVs), recombinant influenza vaccine (RIV), and live attenuated influenza vaccine (LAIV) are expected to be available for the 2019–20 season. Standard-dose, unadjuvanted, inactivated influenza vaccines will be available in quadrivalent formulations (IIV4s). High-dose (HD-IIV3) and adjuvanted (aIIV3) inactivated influenza vaccines will be available in trivalent formulations. Recombinant (RIV4) and live attenuated influenza vaccine (LAIV4) will be available in quadrivalent formulations.

Updates to the recommendations described in the most recent report in MMWR reflect discussions during public meetings of ACIP held on October 25, 2018; February 27, 2019; and June 27, 2019. Primary updates in this report include the following two items:

First, 2019–20 U.S. trivalent influenza vaccines will contain hemagglutinin (HA) derived from an A/Brisbane/02/2018 (H1N1)pdm09–like virus, an A/Kansas/14/2017 (H3N2)–like virus, and a B/Colorado/06/2017–like virus (Victoria lineage). Quadrivalent influenza vaccines will contain HA derived from these three viruses, and a B/Phuket/3073/2013–like virus (Yamagata lineage).

Second, recent labeling changes for two IIV4s, Afluria Quadrivalent and Fluzone Quadrivalent, are discussed. The age indication for Afluria Quadrivalent has been expanded from ≥5 years to ≥6 months. The dose volume for Afluria Quadrivalent is 0.25 mL for children aged 6 through 35 months and 0.5 mL for all persons aged ≥36 months (≥3 years). The dose volume for Fluzone Quadrivalent for children aged 6 through 35 months, which was previously 0.25 mL, is now either 0.25 mL or 0.5 mL. The dose volume for Fluzone Quadrivalent is 0.5 mL for all persons aged ≥36 months (≥3 years).

As Grohskopf, et al. (2019) write, "Influenza viruses typically circulate in the United States annually, most commonly from late fall through early spring. Most persons who contract influenza recover without serious complications or sequelae. However, influenza can result in serious illness, hospitalization, and death, particularly among older adults, very young children, pregnant women, and persons with certain chronic medical conditions. Influenza illness also is an important cause of missed work and school. Routine annual influenza vaccination for all persons aged ≥6 months who do not have contraindications has been recommended by CDC and CDC’s Advisory Committee on Immunization Practices (ACIP) since 2010."

They continue, "The effectiveness of influenza vaccines varies depending on several factors, such as the age and health of the recipient, the types and subtypes 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 influenza 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 is estimated to have prevented 7.1 million illnesses, 3.7 million medical visits, 109,000 hospitalizations, and 8,000 deaths, 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)."

Primary Changes and Updates in the Recommendations
Routine annual influenza vaccination of all persons aged ≥6 months who do not have contraindications continues to be recommended. No preferential recommendation is made for one influenza vaccine product over another for persons for whom more than one licensed, recommended, and appropriate product is available.

Updated information in this report includes the following:
2019–20 U.S. trivalent influenza vaccines will contain hemagglutinin (HA) derived from an A/Brisbane/02/2018 (H1N1)pdm09–like virus, an A/Kansas/14/2017 (H3N2)–like virus, and a B/Colorado/06/2017–like virus (Victoria lineage). Quadrivalent influenza vaccines will contain HA derived from these three viruses and from an additional influenza B vaccine virus, a B/Phuket/3073/2013–like virus (Yamagata lineage). This composition includes updates in the influenza A(H1N1)pdm09 and influenza A(H3N2) components of the vaccine.

Two recent regulatory actions are described:
In October 2018, FDA approved an expanded age indication for Afluria Quadrivalent (IIV4). Previously licensed for persons aged ≥5 years, Afluria Quadrivalent (IIV4) is now licensed for persons aged ≥6 months. The dose volume is 0.25 mL per dose (containing 7.5 µg of HA per vaccine virus) for children aged 6 through 35 months and 0.5 mL per dose (containing 15 µg of HA per vaccine virus) for all persons aged ≥36 months (≥3 years).

In January 2019, FDA approved a change in dose volume for Fluzone Quadrivalent (IIV4). Previously, the dose volume for children aged 6 through 35 months was 0.25 mL (containing 7.5 µg of HA per vaccine virus). Children aged 6 through 35 months who receive Fluzone Quadrivalent may now receive either 0.25 mL (containing 7.5 µg of HA per vaccine virus) or 0.5 mL (containing 15 µg of HA per vaccine virus) per dose. Children aged ≥36 months (≥3 years) and adults should receive 0.5 mL per dose.

Reference: Grohskopf LA, et al. Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2019–20 Influenza Season Recommendations and Reports. Aug. 23, 2019; 68(3);1–21.

Source: CDC