Pfizer vaccine only slightly less effective against key South African mutations - study

Pfizer Inc and Biotech's Covid-19 vaccine appeared to lose only a small bit of effectiveness against an engineered virus with three key mutations from the new coronavirus variant found in SA, according to a laboratory study conducted by the US 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The study by Pfizer and scientists from the University of Texas Medical Branch (UTMB), which has not yet been peer-reviewed, showed a less than two-fold reduction in antibody titer levels, indicating the vaccine would likely be effective in neutralising a virus with the so-called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 received the vaccine. Its findings are limited because it does not look at the full set of mutations found in the new South African variant.

While these findings don't indicate the need for a new vaccine to address the emerging variants, Pfizer and Biotech are prepared to respond if a variant of SARS-CoV-2 shows evidence of escaping immunity by the Covid-19 vaccine, the companies said.

The scientists are now engineering a virus with the full set of mutations and expect to have results from that in about 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 SA 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.