Pfizer Inc. and BioNTech SE built the case that their COVID-19 vaccine will protect against the new variant of the coronavirus that emerged in the U.K. with results of another lab trial.

Like previous work out of the University of Texas Medical Branch, the results published on Wednesday showed that antibodies in the blood of people who had been vaccinated were able to neutralize a version of the mutant virus that was created in the lab. The study was published on preprint server BioRxiv prior to peer review.

Unlike the earlier study, which focused on one crucial mutation, the new research tested all 10 mutations located on the virus’s spike protein, which helps it bind to cells in the host.

It’s a promising but not conclusive result, as scientists continue to closely monitor whether mutations in the virus may make it necessary to adjust the vaccines.

Antibodies in the blood of 16 volunteers in a previous German trial of the vaccine were just as effective against the lab-created mutant strain as they were against the original virus.

The result “makes it very unlikely that the U.K. variant viruses will escape” protection from the vaccine, wrote the research team, led by BioNTech Chief Executive Officer Ugur Sahin.

The BioNTech team is nevertheless ready to adapt the vaccine if needed in the future, it said. That could become necessary to protect against other strains amid evidence another variant that emerged in South Africa may be harder to check.

A separate study on that strain raised concern. Scientists found that half of the blood samples from a handful of patients who already had Covid-19 don’t have the antibodies needed to protect against the South African variant, which is spreading around the globe.

The findings, from South Africa’s National Institute for Communicable Diseases, suggest that those individuals may no longer be protected from re-infection.

In the other half, antibody levels were reduced and the risk of re-infection couldn’t be determined, according to the institute. The findings weren’t peer-reviewed and were based on a small sample size.

Separately, a third study from a Rockefeller University team also underlined the importance of keeping a close watch on the effectiveness of vaccines against variants.

The team tested mutations found in the variants first discovered in the U.K. and South Africa, as well as a third from Brazil, in blood samples from 20 volunteers who had gotten either the Pfizer-BioNTech vaccine or a similar shot from Moderna Inc. In their test, the donors’ blood samples weren’t quite as effective at neutralizing the variants.

“Vaccines may need to be updated periodically to avoid potential loss of clinical efficacy,” the Rockefeller team wrote. Like the other studies, their work was presented in pre-print, before peer review.