- The coronavirus vaccine developed by Pfizer and BioNTech is as effective in laboratory testing against a fast-spreading virus variant that originated in the U.K. as it is against the original SARS-CoV-2 strain identified in China, the companies reported Wednesday. The data was published on the medical pre-print service bioRxiv.
- The results are not from human testing, however, and may need to be further confirmed by studies of people who have been vaccinated. Yet the data should ease some of the concerns that mutations will make the U.K. variant, expected to become more prevalent in the coming months, more resistant to vaccination.
- Nearly 9 million doses of the Pfizer and BioNTech vaccine have been given to people in the U.S., out of a total of nearly 16 million administered. (Moderna's shot accounts for the rest.) Public health agencies so far have focused primarily on healthcare workers and older nursing home residents, although the rollout of immunization program is expected to expand widely in coming weeks as more doses become available.
Viruses naturally acquire mutations from copying errors in replication. Over time, these mutations can accumulate, resulting in what's known as "antigenic drift." This process can render vaccines less effective. With some infectious diseases like influenza, shots need to be updated annually to combat the circulating strains.
Coronaviruses are believed to mutate more slowly because of their ability to "proofread" new genetic material. Because the currently circulating SARS-CoV-2 virus has only been in humans a little over a year, however, scientists still have much to learn.
The U.K. strain, called B.22.214.171.124, had 10 amino acid changes in the characteristic "spike" protein, which all of the authorized vaccines target. One of the changes was at a binding site, raising concerns the antibodies stimulated by vaccines wouldn't be able to attach and block the virus as readily.
The data from Pfizer and BioNTech, published yesterday, suggest otherwise. Researchers produced less infectious "pseudoviruses" from the original strain identified in Wuhan, China, and the new U.K. strain, and then exposed them to the serum taken from 16 patients who were given both doses of the vaccine now called Comirnaty in clinical trials. Half of the samples were from patients age 56 to 85.
The researchers found "no biologically significant difference" in the level of neutralizing antibodies — the type of immune proteins that prevent viruses from entering cells and replicating. The finding "makes it very unlikely" the U.K. variant will be able to evade the vaccine's immune response, the researchers wrote.
A separate strain emerging in South Africa has also raised concerns about the vaccines' effectiveness. Speaking last week at the J.P. Morgan Healthcare Conference, BioNTech CEO Ugur Sahin said data from a separate study of Comirnaty's effectiveness in combating that strain were due in 10 days.
Nonetheless, some biopharma companies are preparing for the potential for SARS-CoV-2 to drift further. Vaccine developer Gritstone Oncology on Tuesday announced development of a second generation vaccine that will stimulate a stronger response from immune-fighting white blood cells that it believes can offer broader protection.