Last year’s influenza vaccination reduced the overall risk for flu-related medical visits by 42%, according to the Centers for Disease Control and Prevention.

In an article summarizing influenza activity in the United States during October 2016–May 2017, investigators said that most of the viral strains antigenically characterized at the CDC “were similar to the reference viruses representing the recommended components for the 2016-2017 vaccine.”

In addition, none of the thousands of samples tested showed resistance to the antivirals oseltamivir, zanamivir, and peramivir, said epidemiologist Lenee Blanton, MD, and her associates in the influenza division, National Center for Immunization and Respiratory Diseases in Atlanta.

The 2017-2018 influenza vaccine has been updated to include an additional influenza A (H1N1) component. This change was recommended by the Food and Drug Administration’s Vaccines and Related Biological Products Advisory Committee, based on data from global influenza virologic and epidemiologic surveillance, genetic and antigenic characterization, human serology studies, antiviral susceptibility, and the availability of candidate influenza viruses ( MMWR. 2017;66[25]:668-76 ).

Preliminary data show that, during the 2016-2017 flu season, there were 18,184 laboratory-confirmed, flu-related hospitalizations, for an overall incidence of 65 per 100,000 population, more than double that for the 2015-2017 season (31/100,000). Broken down by age groups, the rates per 100,000 population in this past season were 44 at ages 0-4 years, 17 at ages 5-17 years, 20 at ages 18-49 years, and 65 at ages 50-64 years, compared with 291 at ages 65 years and older. Finalized estimates of the number of influenza illnesses, medical visits, and hospitalizations averted by vaccination during the 2016-2017 season will be published in December, the investigators said.