Moderna 'booster shot' effective against Brazil, South Africa COVID variants in new trials

A single dose of Moderna booster shot  mRNA-1273 or mRNA-1273.351 rapidly increased antibody response against the Brazil and South Africa COVID-19 variants of concern (B.1.351, P.1), the pharmaceutical firm said in a release on Wednesday. Announcing the initial data from its modified vaccine’s Phase 2 study, Moderna said that 50 µg dose shots administered to the previously vaccinated individuals increased neutralizing antibody titer responses against both SARS-CoV-2 and its variants. The results were submitted as a preprint to bioRxiv and would be peer-reviewed for publication. 

“As we seek to defeat the ongoing pandemic, we remain committed to being proactive as the virus evolves. 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,” said Stéphane Bancel, Chief Executive Officer of Moderna in a statement.

According to CEO Bancel, the firm’s mRNA platform allowed for rapid design of vaccine candidates that incorporate key virus mutations, potentially allowing for faster development of future alternative variant-matched vaccines. “We look forward to sharing data on our multivalent booster candidate, mRNA-1273.211, which combines mRNA-1273 and mRNA-1273.351 in a single vaccine, when available,” he said. 

Booster 'more effective' against South Africa variant 

Moderna’s new multivalent booster candidate combined a 50-50 mix of mRNA-1273, Moderna’s authorized vaccine against ancestral strain SARS-CoV-2. The preliminary data was assembled approximately two weeks following administration of a booster dose of mRNA-1273 or mRNA-1273.351 among the fully inoculated population, nearly 6 to 8 months after their primary vaccination series. Booster mRNA-1273.351 appeared to be “more effective" at increasing neutralization B.1.351 variant, with defense mechanism starting just about 15 days following booster dose. According to Moderna, there was a 7.7-fold difference prior to boosting to a 2.6-fold difference 15 days after a boost, suggesting a “potentially more balanced immune response” against the tested variants. The results came from at least 40-person trial testing for both Moderna's existing shot and a version developed booster. Moreover, the side effects remained minimal and similar to what the volunteers reported in the previous studies after their second dose of the Moderna vaccine.