ANDREW KELLY FILE PHOTO REUTERS An experimental vaccine provided broad protection against all 20 known influenza A and B virus subtypes in initial tests in mice and ferrets, potentially opening a pathway to a universal flu shot that could prevent future epidemics, according to a US study published on Thursday.
The two-dose vaccine uses the same messenger RNA mRNA technology that is used in the COVID 19 shots developed by Pfizer with BioNTech and Moderna. It delivers tiny lipid particles containing mRNA instructions for cells to create replicas of so-called hemagglutinin proteins that appear on influenza virus surfaces.
A universal vaccine would replace the guess work that goes into developing annual shots months ahead of flu season.
The idea is to have a vaccine that will give people a baseline level of immune memory to different flu strains, so there will be less disease and death when the next flu epidemic occurs, according to Scott Hensley, the study leader at the Perelman School of Medicine at the University of Pennsylvania.
The experimental vaccine contains 20 different types of flu vaccines, which are intended to get the immune system to recognize any flu virus it might encounter in the future, unlike standard flu vaccines that deliver one or two versions of hemagglutinin.
In lab experiments, the immune systems of the animals recognized the hemagglutinin proteins and defended against 18 different strains of influenza A and two strains of influenza B. According to a report published in the journal Science, antibody levels induced by the vaccine remained unchanged for at least four months.
The vaccine reduced symptoms of illness and protected the ferrets from death even when they were exposed to a different type of flu not in the vaccine, the researchers said.
Moderna and Pfizer both have mRNA flu vaccines in late-stage human trials, and GSK and partner CureVac are testing an mRNA flu vaccine in an early stage safety trial in humans. These vaccines are designed to defend against only four recently circulating influenza strains, but could theoretically be changed up each year.
The universal flu vaccine, if successful in human trials, wouldn't necessarily prevent infection. Hensley said that the goal is to provide durable protection against severe disease and death.
Alyson Kelvin and Darryl Falzarano, of the University of Saskatchewan, Canada, wrote in a commentary on the study, arguing the effectiveness and potential regulatory requirements for a vaccine against possible future viruses that are not currently circulating.
Adolfo Garc a-Sastrem, director of the Institute for Global Health and Emerging Pathogens at Mount Sinai Hospital in New York, said in a statement that the vaccine shows that there is a protective capacity against all subtypes of influenza viruses.