Moderna says Covid-19 vaccine booster increased immune response against variants of concern
About a month after announcing their variant-specific Covid-19 vaccine boosters showed promising results in mice, Moderna says it now has some human data to back it up.
Volunteers given a booster shot about six to eight months after receiving their second dose saw increased antibody levels against SARS-CoV-2 and two variants of concern: B.1.351, which was first identified in South Africa, and P.1, first identified in Brazil, the company said on Wednesday.
The analysis came from participants who were given either a third dose of mRNA-1273 (the original vaccine currently authorized in the US), or mRNA-1273.351, a strain-matched booster targeting the B.1.351 variant. Moderna is currently testing mRNA-1273.211 — a 50/50 combination of mRNA 1273 and mRNA-1273.351 — in a different arm of the Phase II study.
Following a boost of either mRNA-1273 or mRNA-1273.351, participants’ neutralizing antibodies increased to levels similar to or higher than those seen against the ancestral strain after first vaccination, Moderna said. Fifteen days post-booster, the variant-specific shot appeared to be more effective than the original vaccine at increasing antibody levels against the B.1.351 strain, producing geometric mean titer levels more than one-and-a-half times higher than mRNA-1273.
Also from the results:
The relative decrease in neutralizing titers between the wild-type (D614G) and B.1.351 assays also improved with mRNA-1273.351 booster, from a 7.7-fold difference prior to boost to a 2.6-fold difference 15 days after boost, suggesting a potentially more balanced immune response against the tested variants.
Safety and tolerability data were “generally comparable” to those seen after the second dose of the original vaccine in previous Phase II and III trials, Moderna said. The results have been submitted as a preprint to bioRxiv, and will be submitted for peer-reviewed publication after Moderna wraps up the mRNA-1273.211 portion of the study.
“We are encouraged by these new data, which reinforce our confidence that our booster strategy should be protective against these newly detected variants. The strong and rapid boost in titers to levels above primary vaccination also clearly demonstrates the ability of mRNA-1273 to induce immune memory,” CEO Stéphane Bancel said in a statement.
Bancel told Endpoints News last month that he expects the virus to mutate very quickly in the next couple years, due to the fact that many people haven’t yet been vaccinated or infected. He believes there will be a need for several boosts over the next couple years, “especially people at high risk.” Then in 2023 or 2024, as the speed at which the vaccine mutates slows down, a boost per year might be enough, he said.
“Our mRNA platform allows for rapid design of vaccine candidates that incorporate key virus mutations, potentially allowing for faster development of future alternative variant-matched vaccines should they be needed,” Bancel said Wednesday.