The Oxford / AstraZeneca Covid-19 vaccine does not appear to offer protection against mild and moderate disease caused by the viral variant first identified in South Africa, according to a study to be published on Monday.
Although none of the more than 2,000 patients in the study died or was hospitalized, the findings, which have not yet been reviewed by peers, could complicate the race to launch vaccines as new strains emerge.
In both human trials and blood tests of vaccinees, the jab showed significantly reduced efficacy against the 501Y.V2 viral variant, which is dominant in South Africa, according to the randomized double-blind study seen by the Financial Times.
“A two-dose regimen of [the vaccine] showed no mild to moderate protection against Covid-19 due to [the South African variant]”Says the study, adding that the effectiveness against severe Covid-19, hospitalizations and deaths has not yet been determined.
The so-called Kent variant – which Oxford University said on Friday was as susceptible to the vaccine as the older variants of the virus – has now acquired the E484K mutation, which is present in the variants that fuel Covid-19 outbreaks in Brazil and South Africa .
There are caveats to the study, as the sample sizes were relatively small. The study, led by the University of Witwatersrand of South Africa and the University of Oxford, enrolled 2,026 HIV-negative individuals, with an average age of 31 years. Half of the group received at least one dose of placebo, with the other half receiving at least one dose of vaccine.
Tulio de Oliveira, who heads the Genomic Surveillance Network in South Africa, told the Financial Times that the findings were an “alert to control the virus and increase the response to Covid-19 in the world”.
Health officials around the world expect vaccines to reduce or completely eliminate the burden of hospitalization, which would allow blocking to be eased.
Although important, it is relatively less urgent to avoid symptomatic infection, but milder, which does not progress to hospitalization.
Any setback to the effectiveness of the Oxford / AstraZeneca vaccine would be particularly crucial for the developing world, as partners are producing billions of non-profit doses during the pandemic.
The vaccine still appears to be fully effective in preventing hospitalization and death from other variants of the coronavirus, according to data from other studies.
AstraZeneca declined to comment and referred the questions to Oxford. Oxford declined to comment on the results of the study, saying only that he was working with partners around the world, including in South Africa, to assess the effects of new variants on the first generation of his Covid vaccine.
“Oxford is working with AstraZeneca to optimize the pipeline needed for a change of strain, if necessary,” said the university. “This is the same problem faced by all vaccine developers, and we will continue to monitor the emergence of new variants that emerge promptly for a future strain change.”
The University of the Witwatersrand did not respond to requests for comment. The South African Department of Health did not immediately respond to a request for comment.
Although all Covid-19 vaccines have so far largely resisted variant B.1.1.7 that emerged in the UK, the strain originating in South Africa has been of more concern. Both Johnson & Johnson and Novavax said their vaccines were less effective against the strain in clinical trials conducted in South Africa. In the tests, both vaccines offered complete protection against serious illness and death over Covid-19.
Moderna said it would test a booster injection and a reformulated vaccine to target the South African variant, after studies showed its vaccine was significantly less effective.
BioNTech / Pfizer said its vaccine was slightly less effective in a laboratory study using a pseudovirus with some 501Y.V2 mutations, but did not publish the results of tests against the variant itself.
The 501Y.V2 variant, dominant in South Africa, was recently discovered in countries around the world, including the USA and the United Kingdom.
South Africa received delivery of 1 million doses of the AstraZeneca vaccine last week, the first Covid-19 vaccines to arrive in the country, as part of an order for 1.5 million doses from the Indian Serum Institute.