The Covid-19 vaccine developed by AstraZeneca and the University of Oxford protected people against a new, more contagious variant of the coronavirus at levels similar to the protection offered against other strains of the virus, Oxford researchers said in an article released on Friday.
The article, which has not yet been peer-reviewed, said the vaccine was 74.6% effective against the new variant, which was first detected in Britain and is known as B.1.1.7. This was similar, though potentially slightly less than, in its effectiveness against other strains of the virus.
The encouraging results, although preliminary, suggest that all five major vaccines may offer at least some protection against new variants of the virus that spread around the world. Still, the growing evidence suggests that mutant viruses may decrease the effectiveness of vaccines, increasing pressure on countries to rapidly vaccinate their populations and overcome the variants that are occurring worldwide.
In clinical trials, the AstraZeneca-Oxford vaccine protected all participants from serious illness or death.
The Oxford scientists responsible for the vaccine collected weekly nose and throat samples from participants enrolled in their clinical trial in Britain. To determine the effectiveness of the vaccine against the new variant, they sequenced the viral particles from several hundred swabs between October 1 and January 14, when the new variant was known to be present in Britain.
The vaccine was 84 percent effective against other strains of the virus, compared with 74.6 percent against the new variant, although scientists did not have enough statistical confidence to know for sure whether the vaccine was slightly less effective against the variant.
Andrew Pollard, the lead investigator for the Oxford vaccine trial, said at a news conference that the new data shows that the vaccine has “very similar” levels of effectiveness against the original pandemic virus and the variant that was quickly in the UK and some other countries.
The researchers also performed laboratory tests on blood samples from clinical trial participants who had been vaccinated. They found a nine-fold reduction in activity levels of antibodies generated by the vaccine against variant B.1.1.7 compared to another strain of the variant. This is a sign that the vaccine may have less power to neutralize the variant, although it appears to be still potent enough to be protective.
The variant first detected in Britain has been reported in more than 70 other countries. Public Health England estimated that the variant’s infection rate is 25% to 40% higher than that of other forms of the coronavirus.
Preliminary data from laboratory tests of the Pfizer and Moderna vaccines suggest that they offer good protection against variant B.1.1.7. Novavax, which sequenced test samples from its clinical trial participants in Britain while the variant was circulating widely there, found that its vaccine was highly effective against variant B.1.1.7.
The article released on Friday did not address the protective power of the AstraZeneca vaccine against another rapidly spreading coronavirus variant, known as B.1.351, which was first identified in South Africa. Researchers are conducting similar laboratory tests for try to measure the effect of this variant on the potency of the vaccine.
The AstraZeneca vaccine has been authorized in almost 50 countries around the world, but not in the United States, where the Food and Drug Administration is awaiting data from a clinical trial involving more than 30,000 participants, mostly Americans. The results of this study are expected in March.
In the United States, variant B.1.1.7 has been identified in 33 states, but the full extent of its spread is unknown due to the lack of a national surveillance program. Federal health officials have warned that it could become the dominant form of the virus in the United States by March.