Less than a week after South Africa brought in a million Oxford/AstraZeneca vaccines to the country, health officials have put its distribution on hold, citing concerns around its efficacy.
In a media briefing on Sunday evening (7 February), Professor of Vaccinology at Wits University, Shabir Madhi, said that a vaccine trial done by his team found that there is no proof of the vaccine’s full efficacy against the local variant of Covid-19.
Madhi says that up until the end of October 2020, the vaccine showed ‘potential’ and individuals who took a single dose were 75% less likely to be infected.
However, the emergence of the 501.V2 variant in South Africa means that the Oxford/AstraZeneca vaccine is not as effective.
“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.
He said 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.
Effectiveness of vaccine
South Africa received a million doses of the AstraZeneca vaccine from the Serum Institute of India this week, with another batch of 500,000 doses set to be delivered later this month.
The vaccine has previously been shown to have an efficacy of between 63% and 90% on two doses, but to date it was not certain how effective it would be against new Covid-19 variants.
A study, first reported on by the Financial Times on Saturday evening, found that the vaccine “showed significantly reduced efficacy against the 501Y.V2 viral variant”.
Some good news is that the vaccine is expected to protect against severe disease and death thanks to its neutralising antibody activity similar to other vaccines.
AstraZeneca said it is currently adapting the vaccine to protect against the 501Y.V2 variant and that the clinical development is expected to advance rapidly.
Similarly, trials by Novavax and Johnson & Johnson both showed that their vaccine is less effective against the South African variant.
The Novavax vaccine was seen to be 89% effective overall and 86% effective against the UK variant, however in the trial where most people had the South African Covid-19 variant, the vaccine proved to be just 50% effective.
A trial by Johnson & Johnson showed its vaccine to be 66% effective overall at preventing Covid-19, but dropped to just 57% in South Africa.