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 not mean an end to flu seasons, but would replace the guess work that goes into developing annual shots months ahead of flu season each year. Moderna and Pfizer both have mRNA flu vaccines in late-stage human trials, and GSK (GSK.L) and partner CureVac (5CV.DE) 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, would not necessarily prevent infection.

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