Pfizer vaccine only slightly less effective against key S.African variant: Study

Pfizer Inc and BioNTech's COVID-19 vaccine appeared to only lose a small bit of effectiveness against an engineered virus with three key mutations from the new variant found in South Africa, according to a laboratory study conducted by the U.S. drugmaker.

The study by Pfizer and scientists from the University of Texas Medical Branch (UTMB), which has not yet been peer-reviewed, showed a less than two-fold reduction in antibody titer levels, indicating the vaccine would likely still be effective in neutralizing a virus with the so-called E484K and N501Y mutations found in the South African variant.

The study was conducted on blood taken from people who had been given the vaccine. Its findings are limited, because it does not look at the full set of mutations found in the new South African variant.

The scientists are currently engineering a virus with the full set of mutations and expect to have results from that in around two weeks, according to Pei-Yong Shi, an author of the study and a professor at UTMB.

The results are more encouraging than another non-peer reviewed study from scientists at Columbia University earlier on Wednesday which used a slightly different method and showed antibodies generated by the shots were significantly less effective against the South Africa variant.

One possible reason for the difference could be that the Pfizer findings are based on an engineered coronavirus, and the Columbia study used a pseudovirus based on the vesicular stomatitis virus, a different type of virus, UTMB's Shi said. He said he believes that finding in pseudoviruses should be validated using the real virus.

The study also showed even better results against several key mutations from the highly transmissible UK variant of the virus. Shi said they were also working on an engineered virus with the full set of mutations from that variant as well.