Pfizer says the South African variant could significantly reduce vaccine protection

(Reuters) – A lab study suggests the South African variant of the coronavirus could reduce the antibody protection provided by the Pfizer Inc / BioNTech SE vaccine by two-thirds, and it is not clear if the shot will be effective against the mutation, the companies said Wednesday.

The study found the vaccine was still able to neutralize the virus, and there is still no evidence from human trials that the variant reduces vaccine protection, the companies said.

Still, they are making investments and talking to regulators about developing an updated version of their mRNA vaccine or a booster shot, if needed.

For the study, scientists at the companies and the University of Texas Medical Branch (UTMB) developed an engineered virus that contained the same mutations as the spike portion of the highly contagious coronavirus variant first discovered in South Africa, known as B. 1,351. The spike, used by the virus to enter human cells, is the primary target of many COVID-19 vaccines.

Researchers tested the engineered virus against blood taken from people who had received the vaccine and found a two-thirds reduction in the level of neutralizing antibodies compared to its effect on the most common version of the virus found in US studies.

Their findings are published in the New England Journal of Medicine (NEJM).

Because there is not yet an established benchmark to determine what level of antibodies are needed to protect against the virus, it is unclear whether that two-thirds reduction renders the vaccine ineffective against the variant that is spreading around the world.

However, UTMB professor and study co-author Pei-Yong Shi said he believes the Pfizer vaccine is likely to be protective against the variant.

“We don’t know what the minimum number of neutralizations is. We don’t have that limit, ”he said, adding that he suspects the observed immune response will be significantly higher than is necessary to provide protection.

That’s because in clinical studies, both the Pfizer / BioNTech vaccine and a similar injection from Moderna Inc provided some protection after a single dose with an antibody response lower than the reduced levels caused by the South African variant in the laboratory study.

Even if the variant in question significantly reduces effectiveness, the vaccine should still help protect against serious illness and death, he noted. Health experts have said this is the most important factor in keeping stretched healthcare systems from becoming overwhelmed.

More work is needed to understand whether the vaccine works against the South African variant, Shi said, including clinical trials and the development of correlates of protection – the benchmarks for determining which antibody levels are protective.

Pfizer and BioNTech said they were doing similar lab work to understand whether their vaccine is effective against another variant first found in Brazil.

Moderna published a correspondence in NEJM on Wednesday with similar data previously disclosed elsewhere that showed a six-fold decrease in antibody levels compared to the South African variant.

Moderna also said the actual efficacy of his vaccine against the South African variant has yet to be determined. The company has previously said it thinks the vaccine will work against the variant.