Animal experiments to date have shown that booster doses of the vaccine, which have been specifically tailored to the Omicron variant of the coronavirus, provide only minor advantages over existing Covid-19 vaccines.
As Omicron continues to spread globally, vaccine manufacturers have begun clinical trials of “cut and sewn” vaccines of this highly contagious variant. But early animal studies show that a booster dose, especially against Omicron, does not appear to offer a significant benefit, higher than the third dose of existing vaccines, according to Nature.
Although most research is limited to a small number of animals and none has yet been published in a scientific journal, there is already a growing perception that such a booster dose of a vaccine specifically against Omicron will not change the game against it.
“What we see from these preclinical studies in animal models is that a booster dose of a vaccine, especially against this variant, does not have a really better effect than a booster dose of a current vaccine,” said Dr. David Montefiori. of Duke University Medical Center, North Carolina.
Both Pfizer / BioNTech and Moderna announced in late January that they had begun clinical trials of vaccines specifically against Omicron in humans, and their results are expected in a few months. Pending these results, initial scientific publications of animal studies provide a first “taste” of the potential usefulness of these adapted vaccines.
One study looked at the immune responses of eight macaque monkeys that made two doses of the existing Moderna vaccine and a third dose of either the same existing vaccine or that developed specifically against Omicron. The animals showed a broad immune response to all coronavirus variants, including Omicron, and also had a positive effect on memory B cells.
But one of the researchers, Robert Center, an immunologist at the US National Institute of Allergy and Infectious Diseases, said: “We can still cover all known variants with a booster dose of current vaccines.” Omicron did not show a significant advantage over the existing vaccine.
Another study in mice found that administering a booster vaccine specifically against Omicron, after two doses of mRNA, did not provide any additional benefit compared to the third dose of an existing vaccine. Two other studies in rodents also yielded similar results.
The scientific community is now awaiting the results of evolving human studies of the Pfizer / BioNTech and Moderna Omicron-specific vaccines under development, in order to reach a definitive conclusion about their value.
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