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2 new influenza strains recommended for next season



– In an effort to better match the vaccine to the virus, federal advisors have recommended two new strains be swapped into the 2018-2019 quadrivalent influenza vaccine.

The updates should be the influenza A(H3N2) component and the influenza B components.

Singapore A(H3N2) and the B/Colorado/06/2017-like virus (B/Victoria/2/87 lineage) are recommended be added to A/Michigan/45/2015 (H1N1)pdm09-like virus and B/Phuket/3073/2013-like virus (B/Yamagata/16/88 lineage) for the upcoming season, according to a near-unanimous vote at a meeting of the Food and Drug Administration Vaccines and Related Biological Products Advisory Committee.

Trivalent vaccines should include the same strains, with the exception of B/Phuket/3073/2013-like virus (B/Yamagata/16/88 lineage), the committee recommended.

The panel voted separately on the strains, and all votes were unanimous, except for the vote on the B/Colorado/06/2017-like virus (B/Victoria/2/87 lineage) in the trivalent vaccine, which was supported with 11 positive votes with 1 abstention.The advisory committee’s recommendation is identical to the recommendations recently made by the World Health Organization for next season’s influenza vaccines in the Northern Hemisphere. The WHO recommended that trivalent vaccines contain A/Michigan/45/2015 (H1N1)pdm09-like virus, A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus, and B/Colorado/06/2017-like virus (B/Victoria/2/87 lineage). WHO also recommended that quadrivalent vaccines contain all of the above strains and B/Phuket/3073/2013-like virus (B/Yamagata/16/88 lineage) as the second influenza B strain.

Most of the influenza activity in the United States this season is due to influenza A (H3N2) viruses (67%), according to Lisa Grohskopf, MD, associate chief for policy & liaison in the Influenza Division at the Centers for Disease Control and Prevention. Fortunately, the majority of circulating strains are similar to those contained in the 2017-2018 vaccine. Only strains with B/Victoria lineage displayed antigenic drift, but represented less than 1% of all circulating viruses.

Hospitalization rates for laboratory-confirmed influenza this season have been markedly higher among people aged 65 years and older, compared with younger age groups, and have increased since last season. As of Feb. 17, the preliminary estimate of hospitalizations in this age group was 322.7 cases per 100,000 people, compared with about 290.5 per 100,000 during the 2016-2017 season. There have been 97 pediatric deaths associated with influenza, compared with 110 reported during the 2016-2017 season, 93 during 2015-2016, and 148 during 2014-2015.

These data are not final because the flu season is still ongoing, but a full analysis will be provided at the end of the season, Dr. Grohskopf pointed out.With H3N2 strains of influenza A predominating, questions on the effectiveness of the newly recommended Singapore A(H3N2) were raised by the committee. Jacqueline Katz, PhD, director of the WHO Collaborating Center for Surveillance, Epidemiology, and Control of Influenza, reassured the committee.

“Yes, in fact, it does cover them very well. The majority of the viruses that we’ve tested at the CDC were that emerging 3C2a2 [clade of H3N2] group, and the Singapore virus covered those very well. In general, that’s why we went with Singapore,” she said.

Dr. Katz added that one of the reasons Singapore is so effective is because of its position in the lineage of these flu strains. “It’s at the base of the [phylogenetic] tree; it’s not on the tip of the tree where things are changing, so it’s a more conservative selection.”

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