‘Disappointment’ as experts confirm Covid vaccine that arrived in SA not effective against mild infection

It’s “largely disappointing news”: the AstraZeneca vaccine that arrived in SA last week is not particularly effective against mild to moderate disease caused by the dominant Covid-19 variant circulating across the country.

Speaking at a briefing on Sunday night, Prof Shabir Madhi of Wits University said studies were done in the wake of the new variant – known as 501Y.V2 or B.1.351 – showed it was not statistically significantly effective against mild or moderate infection.

However, he said that it was plausible, and in fact likely, that it was effective against “severe disease” caused by Covid-19.

As a result of the findings, health minister Dr Zweli Mkhize confirmed that the vaccine rollout would be temporarily halted.

Mkhize said it was disappointing, because the country was “ready to roll” . However, there was now a need to look at a “bit more work” around the AstraZeneca vaccine.

“I’ve directed that our scientists must, quickly, sit together and figure out what approach we are going to use in order to effectively deploy the AstraZeneca vaccine. It must be clear when that could be done, what conditions need to be fulfilled, what we need to do about all of this. That is the assignment that is given to our scientists. They'll figure it out.

“So it's a temporary issue that we have to hold on to AstraZeneca. It is temporary until we figure out these issues [and] what are the next steps supposed to be then we bring it back,” he said.

This comes as, last week, the first million doses of the AstraZeneca vaccine arrived in SA, via the Serum Institute of India. The doses were meant for healthcare workers as part of the first phase of the country's vaccine rollout.

According to a Reuters report on Sunday, AstraZeneca said at the weekend that its vaccine - developed with the University of Oxford - appeared to offer only limited protection against mild disease caused by the B.1.351 variant of Covid-19, based on early data from a trial.

The study by Wits and Oxford universities showed the vaccine had significantly reduced efficacy against the South African variant, according to a Financial Times report published earlier in the day.

“In this small phase I/II trial, early data has shown limited efficacy against mild disease primarily due to the B.1.351 South African variant,” an AstraZeneca spokesman said in response to the FT report. “However, we have not been able to properly ascertain its effect against severe disease and hospitalisation given that subjects were predominantly young healthy adults.”

Speaking on Sunday night, Madhi said that, although it wasn’t the intention, when the volunteers had been “exposed to the virus most forcefully” it was a result of infection due to the B.1.351 variant.

“So, inadvertently, the study now provides us an answer as to whether or not this vaccine - and probably indicates what the effect of other vaccines might or might not be - in terms of protection at least against mild, moderate illness, due to this particular variant,” said Madhi.

However, the news, even in the lab, wasn’t good. The tests, done independently at two different labs, found that “much of the antibody that was induced by the vaccine was not actually active against the variant that was currently circulating in SA, the B.1.351 variant”.

“So we’ve seen a substantial drop off, in terms of the ability of the vaccine-induced antibody to neutralise the activity of the virus when tested in the laboratory. Obviously, that would be reason enough to be concerned that the vaccine might not do what we actually set up for it to achieve … if these antibodies are not working that well in the laboratory,” he said.

And, he said, this is what showed with the trial participants.

“So unlike … where we had a 75% reduction of Covid-19 14 days after the first dose of the vaccine until the October 31, when we analysed the individuals in terms of how well the vaccine work against the variant predominantly, what we observed was very little difference in terms of the case accumulation between the vaccine group and the placebo group.

“Consequently, the bottom line, in terms of these results, is that there was a 22% difference - a 22% lower risk of developing Covid-19 - in the vaccinated group, but that was not statistically significant. So we can say that we have not proven that this particular vaccine protects against Covid-19, and particularly against Covid-19 which is a consequence of infection by the B.1.351 variant.

“That is largely disappointing news, but what I need to emphasise again at this point, is that two-thirds of the Covid-19 cases in this particular study were due to mild infection, and the other  third that were due to moderate illness. So what this data doesn’t tell us is whether or not this vaccine might still protect against severe Covid-19, especially individuals that have higher risk of developing severe disease,” said Madhi.

However, in what was promising news, the Johnson & Johnson vaccine did show effectiveness against severe infection - and the effectiveness of the AstraZeneca vaccine was likely to be the same, or similar, for this category of infection.

AstraZeneca said it believed its vaccine could protect against severe disease, given that the neutralising antibody activity was equivalent to that of other Covid-19 vaccines.

“Oxford University and AstraZeneca have started adapting the vaccine against this variant and will advance rapidly through clinical development so that it is ready for autumn delivery should it be needed,” the AstraZeneca spokesman said.