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Sunday, September 25, 2022

CDC Oversells ‘Bivalent’ Covid Shot

 The Centers for Disease Control and Prevention recommends that everyone over the age of 12 receive a “bivalent” Covid-19 vaccine as a booster shot. But only a select group is likely to benefit, and the evidence to date does not support the view that a bivalent vaccine containing Omicron or its subvariants is better than the monovalent vaccine. The CDC risks undermining public confidence by exaggerating the new recording.

Pfizer and Moderna’s existing mRNA vaccines were designed to protect against the original strain of the novel coronavirus known as Wuhan-1. However, the strain that left China was D614G, the first variant. Between January 2020 and December 2021, D614G was replaced by the Alpha variant and then by the Delta variant. In late 2021, Oxford conducted a study to determine whether the mRNA vaccines still protect against serious illness and death from the variants. They did.

Then things changed. In late 2021, the Omicron variant (BA.1) and its subvariants (BA.2, BA.3, BA.4, and BA.5) supplanted Delta. Not only was Omicron more contagious than Delta; it also escaped immunity. Even those fully vaccinated were at risk of mild and some serious illnesses. A third dose was recommended, then a fourth. The CDC found that both a third and fourth dose reduced hospital admissions.

But not everyone benefited. Those who did fell into three groups: the elderly, those with serious health problems, and those with compromised immune systems. With the CDC launching its booster dose campaign in the fall, it would be wise to focus on the at-risk groups rather than the young and healthy.

The new bivalent vaccine contains mRNA from the ancestral strain and BA.4 and BA.5, the subvariants that make up virtually all currently circulating SARS-CoV-2. How does it compare to the old monovalent? We don’t know for sure because the Food and Drug Administration approved the new shot without clinical trials. (As a member of the FDA’s Vaccine Advisory Committee, I voted against approval.) But in June, Pfizer and Moderna presented data on bivalent vaccines containing the ancestral strain plus BA.1. These recordings were carefully examined, and the results were underwhelming.

Participants who received three doses of the original vaccine received a fourth dose of either the original or the bivalent vaccine. Virus-neutralizing antibody responses against BA.1 were greater after the bivalent vaccine, but not at levels that were likely to be clinically significant.

Booster doses for the Moderna vaccine each contained half an adult dose of the ancestral vaccine and BA.1. Moderna will give two booster-dose vaccines that are normally given to children. Pfizer too.

Most worryingly, Moderna recently published a study on the clinical efficacy of the bivalent vaccine containing BA.1. There were 16 cases of SARS-CoV-2 infection: 11 in the bivalent group and five in the monovalent group. Of those suffering from clinical disease, five were in the bivalent group and one in the monovalent group. In other words, although the numbers were small, the monovalent vaccine worked better than the bivalent vaccine.

As we head into the fall, it would make sense to empower those at greatest risk of hospitalization with Covid-19. However, we should be cautious about selling the bivalent vaccine as something better than the existing vaccine until more data is available.

Dr Offit is Director of the Vaccine Education Center at Children’s Hospital of Philadelphia, Professor of Pediatrics at the Perelman School of Medicine at the University of Pennsylvania, and a member of the FDA Vaccine Advisory Committee.

https://news.gerona.ca/

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