The Covid-19 vaccine developed by AstraZeneca and Oxford University protected people from a new, more contagious variant of coronavirus on a similar level as protection against other lineages of the virus, Oxford researchers said in an article published on Friday.

The paper, which has not yet been peer-reviewed, said the vaccine had an effectiveness of 74.6 percent over the new variant, first detected in the UK and known as B.1.1.7. This was similar, if slightly less than, its effectiveness against other lines of the virus.

The encouraging, if preliminary, results suggest that all five leading vaccines may offer at least some protection against new variants of the virus that is found around the world. However, the increasing evidence suggests that mutant viruses can reduce the effectiveness of vaccines and increase pressure on countries to vaccinate their populations quickly and outperform the globally distributed variants.

The Oxford scientists behind the vaccine took weekly swabs from the nose and throat of participants who had taken part in their clinical trial in the UK. To determine the effectiveness of the vaccine against the new variant, they sequenced the virus particles from several hundred swabs between October 1 and January 14. At that time it was known that the new variant was available in Great Britain.

The vaccine had 84 percent effectiveness against other lines of the virus, compared with 74.6 percent against the new variant, although the small sample sizes produced a wide range of estimates.

The researchers also looked at blood samples from clinical trial participants who had been vaccinated and found that the variant may be better able to evade the antibodies produced by the vaccine.

The variant, first discovered in Great Britain, has since been reported in more than 70 other countries. Public Health England has estimated that the infection rate of the variant is 25 to 40 percent 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 was sequencing test samples from its participants in clinical trials in the UK while the variant was widespread there, found that its vaccine against variant B.1.1.7 was highly effective.

The paper, released on Friday, did not address the protective power of the AstraZeneca vaccine against another fast-spreading variant of coronavirus known as B.1.351, which was first identified in South Africa. Researchers are running similar laboratory tests to measure the effect of this variant on the effectiveness of the vaccine.

AstraZeneca’s vaccine has been approved in nearly 50 countries around the world, but not in the United States, where the Food and Drug Administration is waiting for data from a clinical trial that included more than 30,000 participants, mostly Americans. The results of that study could be available this month, and AstraZeneca is expected to have enough safety data to seek emergency clearance from the FDA by the first week of March.

In the United States, variant B.1.1.7 has been identified in 33 states, but the full extent of its prevalence 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.