Pfizer, Moderna COVID-19 vaccines protection against South African variant unclear, studies find

New research suggests a concerning coronavirus variant first identified in South Africa diminished Pfizer and Moderna's vaccine-induced antibody levels, and the level of protection is unclear.

For the Pfizer vaccine, researchers with the University of Texas Medical Branch published findings from a laboratory study in the New England Journal of Medicine. 

Mutations on the B.1.351 strain were genetically engineered into previous strains of the virus to analyze the vaccine’s ability to neutralize the pathogen. Scientists tested the pathogen against blood samples from trial participants who received the vaccine.

"Neutralization of the B.1.351-spike virus was weaker by approximately two thirds," study authors wrote in part, later adding, "it is unclear what effect a reduction in neutralization by approximately two thirds would have on BNT162b2-elicited protection from Covid-19 caused by the B.1.351 lineage of SARS-CoV-2."

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UTMB professor and study co-author Pei-Yong Shi said it is unclear what level of antibodies is needed for protection, but he was hopeful the vaccine will remain effective, Reuters reported. If the variant proves to notably undercut vaccine efficacy, the product can still tamp down hospitalizations and deaths, he said. The outlet noted that scientists in South Africa would convene Thursday with health officials to discuss the study. The country recently suspended rollout of a vaccine developed by AstraZeneca after preliminary findings showed the jab had little impact on curbing mild-to-moderate illness due to the variant.

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While researchers work to understand the findings, Pfizer is drawing plans to create a variant booster shot if necessary.

Moderna also released findings in NEJM on Wednesday, reiterating a previously announced six-fold reduction in vaccine-induced antibodies against the B.1.351 variant, and said protection against the variant has yet to be determined. The company previously voiced confidence the vaccine's ability to protect against the South African and U.K. variants.

"Protection against the B.1.351 variant conferred by the mRNA-1273 vaccine remains to be determined," authors with the Moderna findings wrote. "Our findings underscore the importance of continued viral surveillance and evaluation of vaccine efficacy against new viral variants and may help to facilitate the establishment of correlates of protection in both nonhuman primates and humans."

"A six-fold reduction in neutralizing titers was observed with the B.1.351 variant relative to prior variants," Moderna previously announced. "Despite this reduction, neutralizing titer levels with B.1.351 remain above levels that are expected to be protective."