Egg-Based Flu Vaccines Dealt Another Blow as Researchers Move Closer to Universal Vaccine

For the week ending October 28, 2017, the Center for Disease Control and Prevention’s (CDC) weekly FluView report showed more signs that the 2017-2018 flu season is gaining momentum. The CDC classified influenza activity for the week as regional in Guam and 4 states, local in Puerto Rico and 12 states, and sporadic in the District of Columbia and 31 states. Rhode Island is the only state that is yet to report influenza activity. Of the respiratory specimens testing positive for the virus, 67.9% came up as influenza A and 32.1% were influenza B.

In Washington state, the Tacoma-Pierce County Health Department reported the state’s first flu-related death of the season on November 2, 2017. According to a press release from the department, the victim was a Pierce County man in his 70s who had chronic health conditions that put him at higher risk for serious flu illness. “People can underestimate the severity of the flu, especially for the elderly or others with compromised immune systems,” said Nigel Turner, MPH, the department’s director of communicable disease control. “Everyone should get a flu shot to decrease the likelihood of an outbreak and increase community immunity.” During the 2016-2017 flu season, Washington saw 276 influenza-associated deaths, 242 of which occurred in residents age 65 and older.

Because of the potential severity of influenza infections, researchers are continually investigating influenza viruses, trying to glean as much information as possible on how to combat this pathogens.

Following recent findings on why egg-based flu vaccines aren’t working well to prevent illness, a new study published in the Proceedings of the National Academy of Sciences detailed another reason why the egg-grown vaccine is not protecting against the H3N2 strain of influenza. In 2014 researchers discovered that hemagglutinin gene clade 3C.2a influenza A (H3N2) strain developed a mutation on its outer layer protein, preventing human antibodies from attaching to and destroying the virus. Although the vaccine for the 2016-2017 flu season was updated to include a different protein, the researchers found that the vaccine developed a new mutation while growing in eggs, producing antibodies that were also weak against H3N2. “Our experiments suggest that influenza virus antigens grown in systems other than eggs are more likely to elicit protective antibody responses against H3N2 viruses that are currently circulating,” said study author Scott Hensley, PhD, in a recent press release. “The 2017 vaccine that people are getting now has the same H3N2 strain as the 2016 vaccine, so this could be another difficult year if this season is dominated by H3N2 viruses again.”

Although the flu vaccine continues to be only about 30% effective against H3N2 viruses, the researchers say some protection is better than no protection and still recommend getting a flu shot this season. Before you swear off the vaccine altogether, researchers are making progress towards a universal vaccine.

In another study, published in Scientific Reports, University of Nebraska researchers tested a new flu vaccine made with centralized ancestral genes from 4 major influenza strains. Unlike the seasonal vaccines currently offered each year to protect against circulating viruses, the study’s authors aimed to develop a more universal vaccine able to protect against a broad range of divergent H1, H3, and H5 influenza isolates.

When tested in mice given a lethal dose of influenza A/WS/33 (H1N1), the highest dose of the vaccine offered 100% protection from illness, weight loss, and death. In all, the mice survived exposure to 7 of the 9 viruses tested in the study.

Although this is the first such study on the use of centralized genes in flu vaccines, the authors note that their approach is “scalable and translatable to humans and may provide the foundation for complete and long-lasting anti-influenza immunity.” To this end, lead researcher Eric Weaver, PhD, said in a recent press release that this could be a step toward a novel universal flu vaccine, stating, “The ultimate goal is to be able to vaccinate once and provide lifelong protection.”