Why Was the Flu Vaccine for 2014-2015 Widely Ineffective?

It has been estimated that only one out of 4 people who received the 2014-2015 flu vaccine were protected from the illness.

Influenza vaccines are regularly updated since the virus can mutate over time and resist the counteragent. According to the Centers for Disease Control and Prevention (CDC), 40.3% of American, including adults and children, received the flu vaccine by November 2014. However, new research from The Wistar Institute in Philadelphia, PA revealed that the virus stayed ahead of the most recent vaccination.

“Our studies show that flu viruses recently acquired mutations in critical regions that are recognized by our immune system,” lead author Scott Hensley, PhD, said in a news release.

Every year when the flu vaccine is created, it is meant to address certain viral strains that are predicted to spread. However, viruses can acquire mutations in antibody binding sites of hemagglutinin (HA) in a phenomenon called antigenic drift. The findings published in Cell determined that this occurred in the 2014-2015 H3N2 strain of the flu. There wasn’t just one viral mutation, or even 2 or 3 — the team identified 10 different viral mutations, all of which were not protected by the vaccine.

“We identified mutations that were common in flu isolates in December of 2014 and we engineered viruses that allowed us to characterize these mutations the following month,” said one of the authors Benjamin Chambers, a graduate student.

The team used reverse genetics to find the mismatch between the flu strains and vaccine. The antibody binding sites experienced multiple mutations in the HA antigenic site B which strongly indicates why the A/Texas/50/2012 H3N2 vaccine strain failed in a noteworthy amount of people.

“These new mutations likely contributed to the ineffectiveness of flu vaccines during the 2014-2015 season,” Hensley confirmed.

This study raises concern that other vaccines are not protecting patients as well as expected. The World Health Organization (WHO) announced that the H3N2 part of the flu vaccine will be updated.