Sera of vaccinated individuals was found to neutralize all three SARS-CoV-2 strains studied, which included the variants that have emerged in the UK and South Africa.
Efficacy against the South Africa variant was slightly lower; but the difference was not great enough to create a cause for concern or prompt development of a new vaccine, say the companies.
Earlier this week, Moderna announced similar findings for its vaccine against new strains. It has, however, started developing a booster shot specifically designed to combat the South Africa strain ‘out of an abundance of caution’ as the protection against this strain was lower.
Three strains tested
Last week, Pfizer and BioNTech released results of a previous in vitro study, which showed the vaccine should be effective against the UK strain (B.1.1.7). A new study, published yesterday on pre-print server bioRxiv and submitted to a peer-reviewed journal, now addresses the South Africa strain (B.1.351).
In the study, three mutated viruses were engineered and tested against human sera from 20 participants in the vaccine’s Phase 3 trial.
Of the three recombinant variants, one has a mutation common to both the UK and South Africa variants (N501Y), one has mutations common to the UK variant (Δ69/70+N501Y+D614G), and the third has mutations common to the South Africa variant (E484K+N501Y+D614G). The sera from individuals vaccinated with the Pfizer-BioNTech COVID-19 vaccine neutralized all the SARS-CoV-2 strains tested.
“Consistent with recent reports of the neutralization of variant SARS-CoV-2 or corresponding pseudoviruses by convalescent or post-immunization sera, neutralization against the virus with the three key mutations present in the South African variant (E484K+N501Y+D614G) was slightly lower when compared to neutralization of virus containing the other mutations that were evaluated,” say the companies.
“However, we believe the small differences in viral neutralization observed in these studies are unlikely to lead to a significant reduction in the effectiveness of the vaccine.”
The companies are now evaluating the full set of mutation in the spike protein of the South Africa variant. They say their mRNA vaccine technology is well-suited to developing a new vaccine should this be required against any variant.
