We evaluated vaccine effectiveness (VE) against hospitalization in the test-negative HAIVEN study. Nasal-throat swabs were tested by RT-PCR for influenza and VE was determined based on odds of vaccination by generalized estimating equations. Vaccine-specific antibody was measured in a subset of enrollees.
The 2016-2017 and 2017-2018 influenza seasons were notable for high number of hospitalizations for influenza A(H3N2) despite vaccine and circulating strain match.
Low VE for the A/Hong Kong/4801/2014 vaccine virus in both A(H3N2) seasons emphasizes concerns for continued changes in H3N2 antigenic epitopes, including changes that may impact glycosylation and ultimately reduce VE.
A total of 6,129 adults were enrolled from ten hospitals. Adjusted VE against A(H3N2) was 22.8% (95% C.I. 8.3%, 35.0%), pooled across both years and 49.4% (95% C.I. 34.3%, 61.1%) against B/Yamagata. In 2017-2018, the A(H3N2) VE point estimate for the cell-based vaccine was 43.0% (95% C.I. -36.3%, 76.1%; 56 vaccine recipients) compared to 24.0% (95% C.I. 3.9%, 39.9%) for egg based vaccines. Among 643 with serology data, hemagglutinin antibodies against the egg-based A(H3N2) vaccine strain were increased in influenza-negative individuals.
Martin ET, Cheng C, Petrie JG, Alyanak E, Gaglani M, Middleton DB, Ghamande S, Silveira FP, Murthy K, Zimmerman RK, Monto AS, Trabue C, Talbot HK, Ferdinands JM,. (2020). Low influenza vaccine effectiveness against A(H3N2) associated hospitalizations in the 2016-2017 and 2017-2018 seasons of the Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN). The Journal of infectious diseases