Pfizer, Moderna COVID-19 Vaccines Show Reduction of Protection Against South African Variant

In 2 new studies, both the Pfizer/BioNTech and Moderna vaccines were examined for efficacy looking at neutralizing antibodies with the new variants within a laboratory setting. 

Both studies were reported in the New England Journal of Medicine.

For the Pfizer study, the company collaborated with the University of Texas Medical Branch in looking at blood samples of people that had been administered their vaccine. They engineered S mutations from the B.1.351 (South African) variant into the USA-WA1/2020, an early isolate of the virus.

The investigators took serum samples from 15 vaccine participants in their trial, 2 or 4 weeks after the administration of the booster immunization.

Their results found, “neutralization of Δ242-244+D614G virus was similar and neutralization of the B.1.351-spike virus was weaker by approximately two thirds,” they wrote. “Our data are also consistent with poorer neutralization of the virus with the full set of B.1.351-spike mutations than virus with either subset of mutations and suggested that virus with mutant residues in the receptor-binding site (K417N, E484K, and N501Y) is more poorly neutralized than virus with Δ242-244, which is located in the N-terminal domain of the spike protein.”

With this response, the authors declared it was, “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.”

For the Moderna study, investigators from the company and the National Institutes of Health examined the blood samples of people that had been administered their vaccine and studying the neutralizing antibodies of the B.1.1.7 (United Kingdom), B.1.351 (South African), and other variants including: 20E [EU1], 20A.EU2, N439K-D614G, and the mink cluster 5 variant that was first found in Denmark.

They published their outlining findings from their experiment last month.

For the B.1.351 variant, the investigators did see a reduction in protection. “In serum samples obtained 1 week after the participants received the second dose of vaccine, we detected reductions by a factor of 2.7 in titers of neutralizing antibodies against the partial panel of mutations and by a factor of 6.4 against the full panel of mutations,” they wrote. “However, in serum samples obtained from eight participants in the phase 1 trial, the geometric mean neutralizing titer against B.1.351 was 1:290, and all the serum samples neutralized the rVSV pseudovirus, albeit at relatively low dilutions.”

Currently, with the mixed results in this small sample size, the investigators concluded there was not enough evidence to make an assessment of efficaciousness against the South African variant.

“Protection against the B.1.351 variant conferred by the mRNA-1273 vaccine remains to be determined,” the authors 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.”