How worried should we be about the South Africa variant?

South Africa has suspended its rollout of the AstraZeneca vaccine, after new research prompted fears that the jab is less effective against the coronavirus strain first detected in the country, which now accounts for 90 per cent of the country’s cases.

AstraZeneca’s jab was the first to reach South African soil last week, following the nation’s order of 1.5 million doses. But on Sunday, Dr Zweli Mkhize, the health minister, announced the vaccine would be put on hold and that instead healthcare workers are likely to receive Pfizer or Johnson & Johnson’s vaccines over the coming weeks. “The AstraZeneca vaccine will remain with us, until the scientists give us clear indications as to what we need to do,” he said.

But how worried should we be about the latest research?

It would be misguided to draw the conclusion that the Johnson & Johnson vaccine works on the South African strain and the AstraZeneca vaccine doesn’t. Crucially, unlike J&J’s study, the AstraZeneca study has only provided answers on mild to moderate illness.

The study in question, led by South Africa’s University of the Witwatersrand and Oxford University, recruited 2000 participants, half of which were placed in a placebo group. The AstraZeneca vaccine was found to reduce mild-to-moderate Covid-19 symptoms by just 22 per cent.

The results are concerning when it comes to reducing transmission. As Prof Shabir Madhi, director of the Vaccines & Infectious Diseases Analytics (VIDA) research unit and chief investigator on the trial points out, these findings “shift the focus from the goal of herd immunity” by showing that vaccinated people can still be infected with the virus.

However, the trial did not yield any firm conclusions about whether the AstraZeneca vaccine prevents severe illness from the South African variant. There were no severe cases of illness in the trial group. AstraZeneca said on Saturday that the study was limited by its small size and by the fact that subjects were predominantly young, healthy adults with an average age of 31. “In this age group and with these numbers, the effect on severe disease is going to be hard to estimate,” says Prof Peter Openshaw, Professor of Experimental Medicine at Imperial College London.

Prof Madhi is hopeful that, even if the jab is less effective at reducing the total number of cases, “there might well still be a role for the AstraZeneca vaccine, at least in terms of protecting against severe disease.” He is encouraged by J&J’s trial.

Recent data from the J&J trial on the South African variant found that the vaccine, much like AstraZeneca’s, was less effective at preventing mild forms of illness. When it came to severe cases of Covid-19, however, the jab’s high level of protection was preserved. These results offer hope for the AstraZeneca vaccine; the two jabs have a comparable design and use a similar viral vector.