Uncertainty Remains in the 2019-2020 Flu Vaccine Match

When the CDC announced changes to the 2019-20

vaccine in the spring of 2019, it was with the anticipation that the vaccine would be a much better match to the influenza virus than it has been in the past few seasons.

influenza¹

Vaccines for the 2019-2020 Northern Hemisphere saw updates to both the H3N2 and H1N1 influenza A strains, which had not been updated in a couple of years.

Additionally, all regular-dose and recombinant vaccines are now quadrivalent and therefore covering both lineages of influenza B.

The CDC still continues to recommend that vaccination be offered by the end of October.

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The recommendations for the CDC 2019-2020 quadrivalent influenza vaccine are:²

• A/Kansas/14/2017 (H3N2)-like virus
• A/Brisbane/02/2018 (H1N1)pdm09-like virus
• B/Colorado/06/2017-like virus (Victoria lineage)
• B/Phuket/3073/2013-like virus (Yamagata lineage)

However, a few indicators raise the question about if the vaccine really is as well matched as was anticipated. The influenza season in the Southern Hemisphere generally lasts from April to September and precedes the northern hemisphere’s season. As a result, trends in vaccine effectiveness and influenza infection in the Southern Hemisphere may give clinicians in the Northern Hemisphere potential clues about what to expect.

A recent study indicates that there was an antigenic mismatch of the 2019 Southern Hemisphere influenza vaccine within the H3N2 component.

The H3N2 strain A/Switzerland/8060/2017 was recommended for their seasonal vaccine in 2019. Unfortunately, the strain was ultimately found to have a substitution that results in the loss of a glycosylation site in the antigenic site B of hemagglutinin which is associated with low vaccine effectiveness during H3N2-dominated influenza seasons.

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A version of this article was originally published by Pharmacy Times. VisitPharmacyTimes.comfor the full article and references.