COVID-19 vaccine
COVID-19 vaccineFlash 90

In an update to their COVID-19 vaccine emergency use authorizations, the FDA this week announced that they are “simplify[ing] the vaccination schedule for most individuals.”

The FDA’s press announcement notes that the bivalent (original Wuhan plus Omicron) vaccines are to be used for all doses for people over the age of six months, including for boosters, with the monovalent (original) Moderna and Pfizer-BioNTech vaccines “no longer authorized for use in the United States.”

As such, people who have already received one dose of the original compound “may receive a single dose of a bivalent vaccine.” Most people who have already received the bivalent shot are “not currently eligible for another dose” regardless of how much time has passed since. Those over the age of 65, however, “may receive one additional dose at least four months following their initial bivalent dose.” For those who are immunocompromised, the waiting period between shots is reduced to two months.

Most people who are still unvaccinated are no longer eligible for the original monovalent shot and will be considered fully up-to-date on the COVID vaccine schedule after receiving a single bivalent shot.

The FDA explains the changing guidelines as being due to “evidence ... that most of the U.S. population 5 years of age and older has antibodies to SARS-CoV-2 ... either from vaccination or infection that can serve as a foundation for the protection provided by the bivalent vaccines.”

According to Professor Cyrille Cohen, head of the Laboratory of Tumor Immunology and Immunotherapy at Bar Ilan University, the likely explanation for the change in guidelines is that, “For most of the unvaccinated, a single injection would be equivalent to a booster (second exposure to COVID antigen), because it is likely that they were exposed to SARS-CoV-2 at least once in the past three years.”

He adds that, “While vaccines cannot prevent transmission, they reduce the risk of severe disease. For the general and healthy population, at the present state of affairs, COVID represents less of a threat than it did two years ago and the benefit of additional vaccination is minimal.

“Thus, there is some logic for the FDA to follow a ‘permissive’ policy and somehow recommend a bivalent booster only for the population at risk. We will still need to see what policy the CDC will adopt in this regard.”

Nonetheless, according to an article published in the New England Journal of Medicine in February of this year by Dr. Paul A. Offit, a member of the FDA’s Vaccines and Related Biological Products Advisory Committee, “The strategy for significantly increasing BA.4 and BA.5 neutralizing antibodies using a bivalent vaccine [has] failed,” and there is no reason to believe that the bivalent shots will be any more effective against future variants than they currently are.

Furthermore, the bivalent shots are already outdated, he notes, given that “by December 2022, the BA.4 strain was no longer circulating, and BA.5 accounted for less than 25% of circulating SARS-CoV-2 strains, having been partially replaced by more immune-evasive strains, such as BQ.1, BQ.1.1, BF.7, XBB, and XBB.1.”

If there existed some grounds for giving the bivalent shots the benefit of the doubt at the time of their roll-out, given the lack of human trials at the time (the shots were approved after being tested on eight mice), those grounds no longer exist, after two separate trials demonstrated that the bivalent shots were not significantly more effective against either the prevailing or obsolete strains of Omicron, Dr. Offit adds. The bivalent shots did not elicit either a significant increase in antibody titers or a superior T-cell response.

He attributes the failure of the bivalent shots to what is known as “imprinting,” explaining that, “The immune systems of people immunized with the bivalent vaccine, all of whom had previously been vaccinated, were primed to respond to the ancestral strain of SARS-CoV-2,” and as such, they only responded to the common factors between the original or Wuhan strain, and the strain they were later exposed to.

He adds that, “Given the results of previous studies, it’s likely that this moderate increase in protection against probably generally mild disease will be short lived.”