- In a study, Pfizer and BioNTech's vaccine worked against lab-made coronaviruses similar to variants spreading in the UK and South Africa.
- Small differences in how the vaccine performed against the mutations, versus the original virus, were "unlikely to lead to a significant reduction" in effectiveness.
- The Pfizer-BioNTech vaccine hasn't been tested yet against the real-life coronavirus variants.
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The COVID-19 vaccine co-developed by Pfizer and BioNTech works against lab-made coronaviruses that are similar to the variants found in the UK and South Africa, the drugmakers announced Wednesday.
Studies conducted by Pfizer and the University of Texas showed "small differences" in how well antibodies produced by Pfizer's vaccine bound to and killed the lab-made viruses, compared to how well they worked against the original virus.
But these differences were "unlikely to lead to a significant reduction in the effectiveness of the vaccine," BioNTech said in a press release.
Pfizer and BioNTech's vaccine was 95% effective at protecting against the original coronavirus in trials conducted in 2020.
In the new study, Pfizer tested three different "pseudoviruses" that it had engineered to have some of the mutations found in the UK and South Africa variants. The variant found in South Africa has a mutation called K417N that has been shown to evade antibodies in lab studies — the lab-made variant did not have this mutation.
The Pfizer researchers looked at how well antibodies worked, which is one aspect of the immune system's defense against coronavirus. There is no agreement on how "protection against COVID-19" is defined, the study authors said in the paper, acknowledging this as a weakness of the study.
The results are from a preprint study, and are yet to be published in a peer-reviewed journal to be scrutinized by experts.
The variant found in the UK, B.1.1.7, has been found in several US states, as well as countries around the world. The variant found in South Africa, 501Y.V2, has not yet been identified in the US.
Pfizer said on January 20 that it has tested its vaccine on the variant found in the UK, and it worked in company-run lab studies, but this latest research was its first test against the South Africa variant.
The sample size was small, and the scientists had not performed any statistical-significance tests, which is one way researchers assess whether results could be down to chance.
Moderna announced Monday that its vaccine held up well against B.1.1.7, the variant found in the UK, but small-scale lab tests showed the shot worked less well against the variant found in South Africa, 501.Y.V2.
"Gold standard" would be to test against the real-life variant
In the latest Pfizer study, scientists tested the pseudovirus against the antibodies in 12 blood samples from people who had received two shots of Pfizer's vaccine two or four weeks prior. They then looked at how well the antibodies worked against the pseudovirus variants, compared with the original strain.
"The gold standard would be to test antibodies against the variants themselves to understand how their unique constellation of mutations might affect natural immunity or protection from a vaccine," Dr. Jason McLellan, a structural biologist at the University of Texas at Austin, told the Wall Street Journal. McLellan has studied how coronavirus proteins interact with antibodies, but wasn't involved in the Pfizer study.
Rafael Casellas, a molecular immunologist at the National Institutes of Health (NIH), told the Journal that it was important to keep monitoring coronavirus variants and assess whether vaccines and other treatments might need to be updated, or whether booster shots would be necessary.
"We can't take this virus lightly," he said. "We just don't have enough information so we need to be cautious."
We don't know how long immunity lasts for after receiving a vaccine, for either coronavirus variants or the original virus.
Pfizer said Tuesday that it was already working on booster shots that protect against coronavirus variants. Moderna said Monday that it would develop a new version of its COVID-19 shot to fight 501.Y.V2, the variant found in South Africa.
"Pfizer and BioNTech will continue to monitor emerging SARS-CoV-2 strains and continue to conduct studies to monitor the vaccine's real-world effectiveness," the companies said.
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