A late-season outbreak of H3N2 influenza crippled the flu vaccine’s effectiveness this year, driving it down to just 29% overall.

The flu vaccine offered no protection against the H3N2 strain that dominated at the end of the 2018-19 US flu season, federal officials said last week, leaving overall protection from the disease at only 29%.

Vaccine effectiveness against the H1N1 strain, which predominated the earlier half of the flu season, was 44% against flu illness and 48% to 60% against hospitalization for flu. When combined with a not-statistically significant 9% protection against H3N2, however, overall vaccine effectiveness was 29%.

Read more at www.cidrap.umn.edu