The coronavirus vaccine developed by Pfizer and BioNTech appears to be effective against the mutations that have emerged in South Africa and the UK, according to new laboratory studies. The news has been largely welcomed but it’s not being seen as definitive proof yet about how the vaccine will perform against these mutations.

Coronaviruses frequently mutate as they pass from human to human and, for the most part, don’t significantly alter the virus. Still, a handful of mutations appears to allow the virus to spread faster. These changes happen in the virus’s spike proteins, which are crucial because they enable the virus to enter and take over human cells.

Working with researchers from the University of Texas, Pfizer carried out a study on blood taken from 20 patients who had been given the Covid-19 vaccine. They created two forms of the virus, one with and one without the mutation, and bathed those viruses in the blood samples. Results showed the immune system could take out the new mutation.

The research, which hasn’t been peer-reviewed yet, suggested the vaccine worked to neutralize the so-called N501Y mutation, which has been reported in the variants of the virus discovered in the UK and South Africa. These forms of the virus are spreading faster, which raised questions about the level of protection of vaccines.

“These findings are good news for the likely effectiveness of the Pfizer/BioNTech vaccine against these new variants of SARS-CoV-2,” Michael Baker, an epidemiologist at the University of Otago, told CNBC. “In other words, the Pfizer vaccine is likely to induce immunity that covers the two new more infectious variants.”

Nevertheless, the findings are limited, as the study doesn’t look at the full set of mutations found in either of the new rapidly spreading variants. Researchers now hope to have more information in the next few weeks on whether the vaccines work against the other mutations found in the UK and South Africa variants.

“While it’s reassuring that one mutation within these variants is not associated with escape from vaccines, at least in the laboratory, we urgently need data on these mutations, and preferably on the variant virus with a combination of mutations, as these may act differently in combination” Deepti Gurdasani, a clinical epidemiologist at Queen Mary University of London, told CNBC.

The World Health Organization (WHO) said in December that health authorities were “urgently investigating” whether the N501Y mutation may have any impact on vaccine performance. The variant that emerged in South Africa is of particular concern, as it carries two other mutations in the spike protein that aren’t present in the UK strain.

Still, if the variants eventually mutate in a way that diminishes the efficacy of the vaccines, we aren’t back at square one. The Pfizer and Moderna’s vaccines use mRNA and can potentially be recoded within a few months to combat new variants. However, while the technology allows for it, this has never been tested before.

More than 88.1 million people have so far tested positive for coronavirus worldwide, with 1.9 million deaths, according to data compiled by Johns Hopkins University. Meanwhile, the vaccine campaign is moving along around the world, with more than 17.5 million shots already given in 38 countries, data by Bloomberg showed.

The paper with the results of the study can be accessed here.