Article by Pharmacy Times

“The influenza vaccine for the 2019-2020 flu season will look different than it has for the past few seasons. The FDA’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) and the World Health Organization (WHO) have both selected new strains for each of the 2 Influenza A strains included in the trivalent and quadrivalent vaccines.1-2

Trivalent vaccines will include:

  • Influenza A: A/Kansas/14/2017 (H3N2)-like virus
  • Influenza A: A/Brisbane/02/2018 (H1N1)pdm09-like virus
  • Influenza B: B/Colorado/06/2017-like (Victoria lineage) virus
  • Quadrivalent vaccines will also include a second lineage of the Influenza B virus: B/Phuket/3073/2013-like (Yamagata lineage) virus.1-3

The vaccine selection came after the VRBPAC and the WHO made the uncharacteristic step of delaying the decision on which Influenza A (H3N2) strain to include in the vaccine composition. The 3 other strains in the vaccine were chosen on February 21, 2019 by the WHO and VRBPAC on March 6, 2019. The 2 strains recommended to cover the Victoria and Yamagata lineages of Influenza B remain unchanged. However, experts recommend a new strain for Influenza A (H1N1)pdm09-like virus in February based on data of circulating viruses. The recommendation for the Influenza (H3N2) strain was made by the WHO on March 21, 2019 and chosen for United States vaccines by VRBPAC 1 day later. 1-3

Though postponement of the vaccine composition has occurred before, it is rare. Most influenza vaccines are derived from chicken eggs, which take months to produce. The submission of strain compositions so far in advance is necessary in order to ensure that an appropriate supply of influenza vaccination will be available and distributed by the time flu season begins in the Northern Hemisphere, in October.

The delay is the result of a rise in the proportion of influenza viruses within 1 antigenically distinct group, particularly within the US, Europe, Israel, Asia, and Oceania. The additional time allowed experts more opportunity to monitor circulating influenza viruses and characterization of potential strains to include in the vaccine.1-3 With the majority of circulating influenza strains characterized as Influenza A in recent years, and only about a 44% efficacy rate against these strains, a delay to ensure an increased likelihood of vaccine match for the next flu season seems justified.”

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