Pfizer says South African variant could dramatically reduce vaccine protection

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

The study found that the vaccine was still able to neutralize the virus and there is no evidence yet from trials in people 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, if needed.

For the study, scientists from the University of Texas (UTMB) business and medical branch developed a designed virus that contained the same mutations carried on the peak portion of the highly contagious coronavirus variant first discovered in South Africa, known as B.1.351. The peak, used by the virus to enter human cells, is the primary target for many COVID-19 vaccines.

The researchers tested the modified 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 prevalent in the trials. Americans.

Their results were published in the New England Journal of Medicine (NEJM).

Since there is not yet an established benchmark for determining the level of antibodies needed to protect against the virus, it is unclear whether this two-thirds reduction will render the vaccine ineffective against the variant that is spreading through the virus. world.

However, UTMB professor and study co-author Pei-Yong Shi said he believed Pfizer’s vaccine would likely be protective against the variant.

“We don’t know what the minimum number of neutralizations is. We don’t have that cut-off line, ”he said, adding that he suspects the observed immune response is probably well above what it needs to be to provide protection.

Indeed, in clinical trials, the Pfizer / BioNTech vaccine and a similar vaccine from Moderna Inc conferred some protection after a single dose with an antibody response below the reduced levels caused by the South African variant in the laboratory study. .

Even though the worrisome variant significantly reduces effectiveness, the vaccine should still help protect against serious illness and death, he noted. Health experts said it was the most important factor in preventing overburdened health 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 what levels of antibodies 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 correspondence in the NEJM on Wednesday with similar data previously disclosed elsewhere which showed a six-fold drop in antibody levels compared to the South African variant.

Moderna also said the actual effectiveness of its vaccine against the South African variant remains to be determined. The company has previously said it believes the vaccine will work against the variant.