You might have heard a radio advertisement warning that if you’ve had Covid, you could get it again and experience even worse symptoms. The message, sponsored by the Health and Human Services Department, claims that updated bivalent vaccines will improve your protection.
This is deceptive advertising. But the public-health establishment’s praise for the bivalent shots shouldn’t come as a surprise. Federal agencies took the unprecedented step of ordering vaccine makers to produce them and recommending them without data supporting their safety or efficacy.
The idea of updating mRNA Covid shots every season originally held promise. One advantage of mRNA technology is that manufacturers can tweak the genetic sequence and rapidly produce new vaccines targeting new variants. Hence the bivalent boosters targeting the BA.4 and BA.5 Omicron variants along with the original Wuhan strain.
But three scientific problems have arisen. First, the virus is evolving much faster than the vaccines can be updated. Second, vaccines have hard-wired our immune systems to respond to the original Wuhan strain, so we churn out fewer antibodies that neutralize variants targeted by updated vaccines. Third, antibodies rapidly wane after a few months.
Two studies in the New England Journal of Medicine this month showed that bivalent boosters increase neutralizing antibodies against the BA.4 and BA.5 variants, but not significantly more than the original boosters. In one study, antibody levels after the bivalent boosters were 11 times as high against the Wuhan variant as BA.5.
The authors posit that immune imprinting “may pose a greater challenge than is currently appreciated for inducing robust immunity against SARS-CoV-2 variants.” This isn’t unique to Covid or mRNA vaccines, though boosters may amplify the effect. Our first exposure as children to the flu—whether by infection or vaccination—affects our future response to different strains.
The original Covid vaccines and boosters trained our memory B-cells to produce antibodies against the Wuhan variant. As the University of Pennsylvania’s
Paul Offit
explains in a New England Journal of Medicine article, previously vaccinated people who received the bivalent booster were “primed” to respond to the Wuhan strain and mounted an inferior antibody response to other variants.
The…
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