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CDC Announces Modified Composition for 2018–19 Influenza Vaccine

Atlanta—Public health officials are taking to heart the old adage, “If at first you don’t succeed, try, try again.”

The influenza vaccine for the season now ending was notoriously ineffective against some types of viruses, so the composition is being tweaked in hopes of better results.

The CDC reports that the World Health Organization has recommended the Northern Hemisphere 2018–2019 influenza vaccine composition, and the FDA’s Vaccines and Related Biological Products Advisory Committee has subsequently made the influenza vaccine composition recommendation for the United States.

Both agencies recommend that influenza trivalent vaccines contain an A/Michigan/45/2015 (H1N1)pdm09-like virus, an A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus, and a B/Colorado/06/2017-like (B/Victoria lineage) virus. Quadrivalent vaccines, which have two influenza B viruses, are recommended to contain the viruses in the trivalent vaccines, as well as a B/Phuket/3073/2013-like (B/Yamagata lineage) virus.

“The B recommendation represents a change in the influenza B/Victoria lineage component recommended for the 2017-2018 Northern Hemisphere and 2018 Southern Hemisphere influenza vaccines,” the CDC notes. “The H3N2 recommendation represents an update to the 2017-2018 Northern Hemisphere vaccines, but not to the 2018 Southern Hemisphere vaccines which were recommended to include A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus.”

Public health officials explain that the B component change was made because of the detection and increasing global circulation of an antigenically drifted B/Victoria lineage virus.

The update to the H3N2 component is not a result of antigenic drift, however, but because the egg-propagated A/Singapore vaccine virus is antigenically more similar to circulating viruses than the egg-propagated A/Hong Kong vaccine virus recommended for the Northern Hemisphere 2017-2018 vaccines.

According to the CDC, the vaccine recommendations were based on several factors, including global influenza virologic and epidemiologic surveillance, genetic characterization, antigenic characterization, and the candidate vaccine viruses that are available for production.

Reporting in February, at the height of the just-ending flu season, the CDC conceded relatively low effectiveness of the recommended vaccine, especially against the predominant virus.

For the period November 2, 2017, to February 3, 2018, overall adjusted vaccine effectiveness (VE) against influenza A and influenza B virus infection associated with medically attended acute respiratory infection was 36%. During that time, 69% of influenza infections were caused by A(H3N2) viruses, for which VE was estimated to be 25%, according to the CDC. The news was better for A(H1N1)pdm09 viruses, for which the VE was 67%, and influenza B viruses, for which the VE was 42%.