A single dose of the Moderna coronavirus vaccine given as a booster quickly increased antibody levels in people who had already been vaccinated, the company said on Wednesday.
The antibodies produced by the booster were effective against the original form of the virus as well as against the worrisome variants identified for the first time in South Africa and Brazil. A second booster, which was specially developed against B.1.351, the variant identified in South Africa, generated an even stronger immune response against this variant.
The results come from an early stage of Moderna’s experiment with the boosters and have not yet been published or verified by other scientists. Moderna plans to publish the results on the preprint server bioRxiv, the company announced on Wednesday.
“We are encouraged by this new data, which increases our confidence that our booster strategy should protect against these newly discovered variants,” said Stéphane Bancel, CEO of Moderna, in a statement.
The boosters tested in 40 participants were given as the third shot six to eight months after the two-shot immunization with the current vaccine. Antibodies from the primary vaccination were detectable in 37 of these people, but about half of the participants showed poor performance against the variants that struck South Africa and Brazil. The boosters increased the levels of antibodies against both variants, although the boosters were still slightly less effective than against the original form of the virus.
The mRNA platform used in Pfizer and Moderna vaccines can be easily customized, so companies can produce newer versions within weeks. Moderna began modifying its vaccine to combat the variant identified in South Africa after reports emerged that the existing vaccines against that variant were slightly less effective. The variant carries a mutation that helps the virus bypass the immune system.
Moderna is testing three strategies to improve the immunity of the current vaccine: using the current vaccine as a booster; Using the booster specially designed to combat B.1.351; and a combination of the two in a single vaccine.
Wednesday’s announcement refers to results obtained two weeks after immunization with either a booster of the original vaccine or the booster modified for B.1.351. The company plans to release data at later times and from tests on the combination amplifier as it becomes available.
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