Oxford vaccine only 10% effective against South African variant

londonSouth Africa has suspended plans to immunise its front-line health workers with the Oxford/AstraZeneca vaccine after a small clinical trial suggests it is only 10% effective in preventing mild to moderate cases of the country's dominant variant, which would appear to be more infectious and is driving up the number of cases. Between mid-October and now the number of cases has doubled from 700,000 to more than 1.4 million in just three and a half months.

According to the Minister of Health, Zweli Mkhize, the South African variant already accounts for 90% of cases in the country, and given the preliminary results, authorities have decided to suspend the administration of the Anglo-Swedish vaccine. "AstraZeneca's vaccine appeared to be effective against the original strain, but not against the variant. We have decided to temporarily suspend the deployment of the vaccine. There is more work to be done." Last week, South Africa received over a million and from next week was due to start the immunisation process. The minister said the vaccines, which expire in April, will be held until scientists give clear instructions on what needs to be done.

Professor Shabir Madhi of the University of the Witwatersrand, who leads the study, has said that although the study was small, it was designed to determine whether or not the vaccine has 60% efficacy against severe cases of covid. "The results that we now describe against the variant, the point estimate is 10%. Clearly, that is far off the 60% mark and, even if you had a larger study you are unlikely to get to a vaccine efficacy readout of even 40 or 50%," he told BBC Radio 4's Today programme. “What the study results really tell us is that, in a relatively young age group demographic – with very low prevalence of morbidities such as hypertension and diabetes etc – the vaccine does not protect against mild to moderate infection” he continued.

The baseline study, not yet reviewed, was carried out with 2,000 participants, mostly young and healthy. The average age of the volunteers was 31. Considering these characteristics, protection against moderate-severe diseases, hospitalisation or death could not be evaluated, since the target population had a very low risk of suffering them. "Until the end of October, the AstraZeneca vaccine showed enormous potential in terms of reducing even mild and moderate cases," said Madhi. But the unfortunate reality of viruses, bacteria and most other organisms is that they mutate.

Other vaccines have shown reduced efficacy against the variant, but have provided good protection against severe disease and death. This is the case with the clinical trials of the Johnson & Johnson and Novavax vaccines, both of which are awaiting assessment by the UK regulator - and in the case of Johnson & Johnson, also the US regulator.

The early results of AstraZeneca's variant vaccine could have far-reaching implications, as many other countries in Africa have considered using AstraZeneca's vaccine. The international Covax initiative has purchased hundreds of millions of doses, which are produced by the Serum Institute of India. The first million of the 330 million doses it expects to distribute by June are expected to be delivered as early as next week.

The Oxford/AstraZeneca vaccine developers hope to have a modification of the vaccine ready to tackle the South African variant in the autumn, Sarah Gilbert, a senior researcher with the Oxford team, told the BBC on Sunday: "We are working on a version with the sequence of the South African variant. It seems very likely that we can have a new version ready to use in the autumn.