Pfizer and Moderna vaccines have reduced effectiveness against South African variant, newly published studies show

Live updates: Pfizer and Moderna vaccines have reduced effectiveness against South African variant, newly published studies show

Paulina Firozi

Two of the most promising coronavirus vaccines recently showed reduced effectiveness against the more virulent virus strain first seen in South Africa, according to reports in the New England Journal of Medicine, but also appeared to mobilize enough of an antibody response to neutralize the pathogen.

Experts warned that it was still unclear what level of neutralization is required for protection against the variant, known as B.1.351, that is now the dominant strain in South Africa, and these studies were carried out in a lab setting rather than real life.

“These are in vitro studies and we don’t know if there is a threshold for neutralization that defines protection. In fact, we don’t even know that there is a quantitative correlation between antibodies levels and protection,” noted journal editor in chief, Eric Rubin, in a podcast commenting on the findings. “It is very concerning that we don’t know the clinical significance of these findings.”

The two reports posted Wednesday covered the Pfizer-BioNTech and Moderna vaccines, drawing from studies using genetically engineered versions of the variant against blood samples from volunteers already inoculated against the virus.

The strain has been identified in multiple countries, along with a variant first identified in Britain that scientists say is also highly contagious.

In the case of Moderna, the company published a letter in the journal that included previously disclosed data showing a sixfold drop in antibody levels vs. the South Africa strain, Reuters reported. The shot’s efficacy against the variant has not yet been determined.

According to Pfizer, in testing its vaccine against the variant in a lab, the shot generated about a third of the antibodies that are normally mobilized with the original strain. The activity, however, appeared to be sufficient enough to neutralize the virus.

Still, Pfizer said in a statement Wednesday that it was “taking the necessary steps … to develop and seek authorization” for an updated vaccine or booster shot that could better combat the variant.

In Johannesburg, South African scientists planned to meet Thursday to discuss the Pfizer study, a Health Ministry spokesman told Reuters.

“I do know that our scientists will be meeting to discuss [the study] and they will advise the minister,” Reuters quoted spokesman Popo Maja as saying. “We are not going to be releasing a statement until advised by our scientists. We will also be guided by the regulator.”