Cape Town – A smaller trial in South Africa has shown that Novax’s experimental coronavirus vaccine was not as effective at preventing the disease as in a UK trial.
The vaccine was only 49% effective at preventing symptomatic cases of Covid-19 in the 4 400-participant study, but among people who are HIV-negative it was 60% effective.
Based on a trial of more than 15 000 patients in the UK, the jab was 89% effective at preventing symptomatic Covid-19.
Novax published the results and said it plans to submit them to a scientific journal for review. It maintained that the 60% reduced risk against Covid-19 illness in vaccinated individuals in South Africans underscores its value to combat the variant circulating in South Africa.
What was concerning, however, is the chances of people getting Covid-19 a second time, said Professor Shabir Madhi, executive director of the Vaccines and Infectious Diseases Analytics Research Unit at Wits University, and principal investigator in the Novavax Covid-19 vaccine trial in South Africa.
Tests suggested that nearly a third of the study participants had been previously infected, yet rates of new infections in the placebo group were similar.
"Past infection with early variants of the virus in South Africa does not protect against infection with the new one,’’ Madhi said. "There doesn't seem to be any protection derived."
However, Novavax said it is starting to develop a version of the vaccine that could more specifically target the mutations found in South Africa.
Just over 4 400 participants were enrolled in South Africa's Phase 2b study that started in August last year. It took place as a new variant emerged in South Africa that is more infectious. The variant, B.1.351, was discovered in December and has spread to 30 countries.
“The higher efficacy of the vaccine in the UK than in South Africa is because the variants circulating in SA are less sensitive to vaccine-induced immune responses," said Madhi.
"Nevertheless, the 60% reduced risk against Covid-19 illness in vaccinated individuals in South Africans underscores the value of this vaccine to prevent illness from the highly worrisome variant currently circulating in South Africa, and which is spreading globally.
’’This is the only Covid-19 vaccine for which we now have objective evidence that it protects against the variant dominating in South Africa.”
SA Medical Research Council president and CEO, Professor Glenda Gray, said: "If we can prevent more hospitalisation and deaths, then this is an important outcome.
’’Also, it's important to note that as the new variants start to circulate, we might see a diminishing vaccine effectiveness in other vaccines that are currently being rolled out at a global level.’’
Some preliminary research has raised concerns that current coronavirus vaccines may not work as well against that variant. Pfizer and BioNTech, makers of a coronavirus vaccine, said yesterday, though, their product is effective against the Covid-19 variants that have emerged in the UK and South Africa.
In a statement, the two companies said these preliminary findings "do not indicate the need for a new vaccine to address the emerging variants".
Madhi, who also shared clinical trial data during a late-night webinar, said that the ability of Covid-19 vaccines to impact the pandemic would depend on the product, its efficacy and how quickly we could scale up coverage of the vaccine.
"In the study itself, after 4 400 points, we managed to do sequencing, 93% of all of the cases ended up being the 501Y.V2 variant. So all of the efficacy results is speaking to efficacy in relation to this dominant, mutated virus.’’
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