The findings, released in a preprint paper and not peer-reviewed, also detailed recent analysis showing that one dose of the vaccine can shorten the duration of shedding and viral load among those infected with Sars-CoV-2, which may translate into a reduced transmission of the virus, Oxford University said.
Scientists at Oxford said their candidate delivered similar levels of protection against the British variant, known as B.1.1.7, compared to the original form of the virus that first spread throughout the four nations.
Professor Andrew Pollard, chief investigator on the Oxford vaccine trial, said: “Data from our trials of the ChAdOx1 vaccine in the United Kingdom indicate that the vaccine not only protects against the original pandemic virus, but also protects against the novel variant, B.1.1.7, which caused the surge in disease from the end of 2020 across the UK.”
People who have developed immunity against the virus, either through natural infection or vaccination, may still be capable of carrying and transmitting the pathogen, research indicates.
Analysis is ongoing to establish whether the effectiveness of the Oxford vaccine is diminished by the South African and Brazilian variants, which carry the concerning E484K mutation not seen in B.1.1.7.
This mutation affects the shape of the virus’ spike protein, helping it to escape parts of the immune response triggered by the current generation of vaccines – though they are still expected to offer good protection against illness and severe disease.
Mene Pangalos, chief executive research and development at AstraZeneca, said it would not be surprising to see reduced efficacy against the South African variant.
“I think it’s reasonable to say that what we know from other vaccines is we’re not going to be surprised to see reduced efficacy,” he said.
The Independent reported last month that the Oxford team is adopting an “at-risk” approach to the variants and intends to begin synthesising new versions of the vaccine without waiting to find out if they will be needed, with professor Sarah Gilbert – one of the lead scientists – “actively working on this”.
Downing Street has also indicated that the Medicines and Healthcare products Regulatory Agency (MHRA) will be able to approve modified vaccines as quickly as required in the face of the new and emerging coronavirus variants.
AstraZeneca has said it believes a modified version of the Oxford vaccine – one capable of neutralising the emerging coronavirus variants – could be ready by autumn.
To determine the effectiveness of their vaccine against the UK variant, researchers at Oxford examined swabs taken from volunteers with both symptomatic and asymptomatic infection who had been enrolled into the jab’s large-scale efficacy study.
The scientists then established which coronavirus variants the participants had been infected with after receiving either the vaccine or the placebo.
Further analysis revealed that vaccine efficacy against symptomatic positive infection was similar for B.1.1.7 and non-B.1.1.7 lineages, at 74.6 per cent and 84 per cent respectively.
However, Prof Pollard said it not possible to say whether the efficacy levels were the same or different because of overlapping confidence intervals.
“The important issue is that it’s in a very similar ballpark to the previously reported efficacy and they’re very similar to each other,” he said. “We can’t actually say statistically whether those numbers are actually different. If they were, it’s a relatively small percentage – it’s still in the high 70s or 80s for both.”
Separate studies have shown that the vaccines produced by Johnson & Johnson, Moderna and Novavax still offer protection against the South African variant – roughly 60 per cent in the case of the latter – but are not as effective as they were against the original form of the virus.
Even so, both Johnson & Johnson and Novavax have reported that none of the people who received a vaccine in their South African trials died of Covid-19.
Prof Gilbert, who developed the Oxford vaccine, said: “All viruses accumulate mutations over time, and for influenza vaccines there is a well-known process of global viral surveillance, and selection of strains for an annual update of the vaccines.”