Jeff Greenberg is a contributor.
A new study suggests that this year's flu vaccine is a bad match for the dominant strain of the disease.
The study's co-author, Scott Hensley, a professor of microbiology at the Perelman School of Medicine at the University of Pennsylvania, told CNN that it looked like a major mismatch. The H3N2 subtype of the flu has been looked at by Hensley and his colleagues to see if there are any genetic changes that can be found in the virus. They recently identified a new H3N2 "clade," or a split in the virus's family tree.
They named the clade "3C.2a1b.2a2," or 2a2 for short, and posted their finding on Thursday. The study only measured the responses of 40 people who were mostly young and healthy. The research suggests that the new clade may make the vaccine less effective.
The flu shot is less effective than other vaccines.
That doesn't mean the flu shot was useless.
The authors of the preprint said that studies show that seasonal flu vaccines prevent hospitalizations and deaths even in years with large antigenic mismatches. The vaccines will reduce the odds of death and severe disease even if the flu shot doesn't match the dominant strain.
The 2a2 clade is a problem. The researchers found that the genes that code for hemagglutinin are found on the surface of the virus.
Live Science previously reported that flu vaccines train the immune system to recognize the HAProtein, which juts off the Influenza viruses like a lollipop on a stick. The problem is that the structure of the HA protein can change in the time between when the flu vaccine is developed and when the season starts. H3N2 is the fastest-growing of the four flu strains covered by the annual flu shot.
The vaccine's effectiveness has been undermined in the past due to the fact that the flu shot tends to be least protective against H3N2. The H3N2 virus has changed this year in a way that is similar to the one that weakened the vaccine in the flu season of 2015.
The new 2a2 H3N2 clade was poorly neutralized by the new 2a2 H3N2 vaccine. "55% of vaccinees had undetectable levels of neutralizing antibodies against 2a2 H3N2 after vaccination."
Live Science previously reported that the University of Michigan's Ann Arbor campus had an outbreak of flu cases driven by H3N2. More than 700 people were affected by the surge, of which around 25% werevaccinated against the flu, according to CNN.
Not all is lost. While cases of 2a2 H3N2 infections are quickly rising in the United States and other parts of the world, it is possible that other clades of H3N2 will become predominant in the future. It is possible that H1N1 or Influenza B will dominate later in the season.
CNN has more about the new research.
Live Science published the original article.
