Pfizer Study Suggests Shot Will Work Against Variants

Researchers have been racing to assess whether Covid-19 vaccines and drugs will still work against new variants, as governments roll out shots they hope will allow schools, businesses and other establishments to reopen.

Pfizer’s findings are consistent with other preliminary results reported in recent weeks by several research groups looking at the effectiveness of available vaccines against the new variants.

The research is still preliminary, however. Pfizer’s study was conducted in a lab and tested only a subset of mutations found in the variants, but not the variants themselves. Also, the researchers didn’t assess whether their results were statistically significant.

Yet these and other results suggest that the impact of the variants on the shots will be “relatively modest, which is good news for the vaccines,” said Jason McLellan, a structural biologist at the University of Texas at Austin who has studied how coronavirus proteins interact with antibodies and wasn’t involved in the Pfizer study.

Pfizer said the “findings do not indicate the need for a new vaccine to address the emerging variants.” The company said, however, that it and partner BioNTech SE BNTX -0.30% were prepared to respond to a vaccine-resistant version of the virus.

The Pfizer-BioNTech vaccine uses a new technology named messenger RNA, after the molecular couriers of genetic instructions, which allows developers to make more rapid changes to their vaccines than more traditional techniques. The other vaccine authorized in the U.S., from biotech Moderna Inc., also uses mRNA technology.

A recent preliminary study by Moderna, in collaboration with scientists at the U.S. National Institutes of Health, showed antibodies generated by its vaccine were less effective at binding the mutated spike proteins of the South African variant. The researchers didn’t find a difference for the U.K. variant’s spike proteins. The coronavirus uses its spike proteins, which stud its surface, to enter and infect cells. The proteins are key targets of antibodies.

As a precaution, the company said it was developing a booster shot for the South Africa variant.

The new Pfizer study found that antibodies generated by its vaccine were slightly better at binding versions of the virus that had some of the mutations found in the U.K. variant.

That could be because the scientists tested their U.K. variant-like viruses against a variant that lacked an older, but key mutation that increases transmissibility, but makes the virus more susceptible to antibodies, Dr. McLellan said.

The gold standard would be to test antibodies against the variants themselves, he and others said, to understand how their unique constellation of mutations might affect natural immunity or protection from a vaccine.

Those studies are ongoing in labs around the world.

Pfizer researchers, who worked with scientists at the University of Texas Medical Branch, didn’t perform statistical-significance tests, a key way scientists assess if their results are due to chance and have real-world importance, another important limitation, scientists not involved in the study said.

Rafael Casellas, a molecular immunologist at the NIH, said it was important to keep monitoring the evolution of the coronavirus to assess whether vaccines and other therapies will need to be updated, or whether booster shots will be necessary. “We can’t take this virus lightly,” he said. “We just don’t have enough information so we need to be cautious.”

Write to Daniela Hernandez at [email protected]