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Flu vaccines induce neutralizing antibodies against the hemagglutinin (HA) protein on the surface of the virus. These antibodies typically are directed at the outermost part (the “head”) of the HA protein, a part that changes shape constantly. This shape change is the reason that new flu vaccines are needed each year.
A team from NIH and CDC immunized animals with DNA vaccines against either the H1N1 or the H3N2 flu virus and followed those vaccinations with a traditional peptide flu vaccination. This “one–two punch” produced about 50-fold more neutralizing antibodies than did either the DNA vaccine alone or traditional vaccine alone. More important, many of the neutralizing antibodies were against the innermost part (the “stem”) of the HA p…