What you need to know about vaccine efficacy against the 501Y.V2 Variant

On Sunday, February 7, Health Minister Dr Zweli Mkhize and a panel of leading experts hosted a media briefing to outline new developments in South Africa’s COVID-19 vaccine acquisition and rollout programme.

The briefing came promptly after new studies earlier the same week showed that the Oxford/AstraZeneca vaccine, of which South Africa had procured one million doses from the Serum Institute of India, may not have the same efficacy (or effectiveness) against the mutated COVID-19 501Y.V2 variant – which is predominant in South Africa.

Mkhize said the purpose of the briefing was two-fold: to get experts to share their latest research findings and highlight the implications of such on our fight against COVID-19; and to respond to some of the findings from a public health policy point of view as to how government will be adjusting some of its plans and programmes to accommodate these findings.

Professor Shabir Madhi, who led the clinical trial of the Oxford/AstraZeneca vaccine candidate locally, said they conducted a study using 2000 participants, aged between 18 and 65 years old.

Up until the end of October last year, before the new variant began spreading, Madhi said the vaccine showed “tremendous potential”. He said just 14 days after taking the first of two jabs, participants showed a 75% lesser likelihood of becoming infected with COVID-19.

However, the 501Y.V2 variant then emerged and spread rapidly throughout the country. The study then changed to examine the vaccine’s potency against the original virus as compared to the new strain.

“Much of the antibody induced by the vaccine was not actually active against the variant circulating in SA,” Madhi concluded.

The study showed a “substantial drop” in the vaccine’s ability to neutralise the activity of the virus when tested in the lab.

“When we analysed individuals in terms of how well the vaccine worked against the variant, there was very little difference between the vaccine group and placebo group,” Madhi said.

“However COVID vaccines really remain the only sustainable option of reducing risk of severe disease and death.”

According to Professor Salim Abdool Karim, one of South Africa’s leading COVID-19 experts, these findings do not spell “doom and gloom”.

Karim said that vaccines made by Pfizer and Moderna seem to do “reasonably well” against the 501Y.V2 variant, even with their neutralising activity diminished. He said the Sinopharm vaccine also shows a small reduction in efficacy, about 1.5 fold.

However, he says, there is hope that the Johnson&Johnson vaccine will show a smaller decline in efficacy against the variant, making it a plausible choice for rollout.

“COVID vaccines remain effective against existing variants. The next set of vaccines will be made from the 501Y.V2 variant and so they are likely to be effective against the 501Y.V2 variant. We are expecting two kinds of vaccines: the first are 501Y.V2 boosters and we have already heard about the good progress they are making on these boosters,” he said.


“You will take the existing vaccine to give you immunity against the existing variants and then take this booster which will boost it in order to give you protection from 501Y.V2 variant. A next generation of vaccinations is intended to be much broader and will cover you from the current and future variants. That will take a little longer to develop.”

Karim says the rollout of the AstraZeneca vaccines which have already landed will need to be put on a temporary hold.

“We can still proceed with our rollout but we need to do it wisely by taking a stepped approach,” he said.