Local researchers have welcomed findings for Russia’s Sputnik V viral vector vaccine, which achieved 91.6% efficacy in preventing symptomatic Covid-19 in a phase 3 clinical trial.
They say it is a boost to global efforts to control the pandemic.
Unlike most other phase 3 Covid-19 vaccine trials, the vaccine and control groups in this trial were not the same size, but split in a three-to-one ratio.
The analysis, based on data from nearly 20 000 participants, showed that the two-shot vaccine offered full protection from severe illness.
There were no serious adverse events associated with the vaccine and it was found to be safe and effective in people aged over 60, who are at highest risk for severe disease and death.
The preliminary results do not show whether Sputnik V reduces the risk of transmission or asymptomatic infection and it is not clear how long protection lasts.
The trial is ongoing and aims to include 40 000 people. Monitoring of safety and efficacy is continuing.
Confirmation of Sputnik V’s efficacy and safety is easing scientific scepticism off the Gamaleya Research Institute’s vaccine, after it was given state approval in August before phase 3 testing.
There were concerns at the time that Russia’s premature regulatory approval of the vaccine was driven by geopolitical ambitions.
Sputnik V has been given regulatory approval in 16 countries so far, including Hungary, which broke ranks with the EU last month by becoming the first bloc member to approve it.
The latest data has been submitted to the European regulator for review.
‘Rigorous and positive’ results
Africa Health Research Institute director and vaccinology expert Professor Willem Hanekom says the results are “rigorous and positive, and contribute to the field” of Covid-19 vaccine development.
While the lack of diversity – only white males were included in the study and no mention of the vaccine’s efficacy on HIV – is worth noting, he said “there is a good spread across ages”, from 18 to 60+.
Professor Linda-Gail Bekker, director of the Desmond Tutu HIV Centre and co-leader of the Ensemble Johnson & Johnson trial in South Africa, says the Sputnik V trial is “compelling”.
However, she, like Hanekom, questions the absence of data for HIV-positive people. She says more research is needed to find out whether the vaccine is safe and effective for people living with HIV.
Similar to the Oxford-AstraZeneca vaccine, Sputnik V is a viral vector vaccine, which is based on a modified version of adenovirus, a common cold virus.
This is tailored to carry genetic instructions for making the coronavirus spike protein, which it passes to human cells. The manufactured coronavirus spike protein then triggers an immune response to protect against Covid-19.
Sputnik V, however, uses a different human adenovirus for each of the two doses – initially recombinant human adenovirus type 26 (rAd26-S), followed by a booster shot with type 5 (rAd5-S) to trigger a stronger immune response and reduce the risk of resistance.
Oxford-AstraZeneca uses a double dose of type 26 and Johnson & Johnson a single dose of type 26.
“The only problem I have around the type 5 boost is that the data we have from previous HIV trials using the Ad5 platform was not successful and, worryingly, in certain populations we saw an increased risk of acquiring HIV,” Bekker says.
Another high-efficacy vaccine
A round-up of the current vaccine front-runners puts the Sputnik V vaccine in the same high-efficacy group as the mRNA vaccines made by Moderna and Pfizer-BioNTech, which show efficacy of about 95%.
It is important to note that while efficacy in preventing Covid-19 varies between the six current vaccines, they all appear to be highly effective at preventing severe Covid-19 and death.
Efficacy rates for the Oxford-AstraZeneca vaccine have varied between 62% to 90% in late clinical trials, with most trial results in the lower end of that range.
One million doses of the Covishield vaccine manufactured by the Serum Institute of India, under licence from AstraZeneca, were the first to reach South Africa’s shores. The two-dose vaccine will initially be rolled out to healthcare workers.
Preliminary findings, not yet published in any reputable medical journal, for the single-dose Johnson & Johnson vaccine in phase 3 clinical trials show 66% efficacy overall, with 72% in the US and 57% in South Africa, where the highly transmissible 501Y.V2 variant is dominant.
The vaccine showed 85% efficacy at preventing moderate to severe disease 28 days after vaccination. More than 40 000 participants were enrolled.
Novavax recently announced that its vaccine was 89% effective in its UK phase 3 trial. The South African phase 2B trial of the vaccine suggests 60% efficacy against mild and severe Covid-19 among 94% of trial participants living without HIV.
The 49% overall efficacy in South Africa included HIV-positive volunteers, but the numbers were low, which makes them uncertain.
The researchers say the highly contagious 501Y.V2 variant was responsible for 90% of infections in the South African arm of the study, which enrolled 4 400 volunteers.
‘Phenomenal protection against severe disease’
Hanekom says crucial results showing that the vaccines used in all the trials prevent severe disease and death is being lost, even though it means a heavy weight will be lifted off overburdened hospitals and healthcare workers if people are given vaccines.
“We want vaccines to protect individuals, but we also know we’re going to control the epidemic with more than 50% efficacy. While the higher efficacy vaccines prevent severe disease and death, the Johnson & Johnson, Novavax and Oxford-AstraZeneca vaccines, with lower efficacy rates, have also shown phenomenal protection against severe disease and death. For me, that is by far the most important thing for an individual,” says Hanekom.
Bekker agrees: “If everyone is vaccinated, we know we have a reduced risk of death and severe illness. We need to get away from the idea that we are going to stop infection in everyone 100% … We need to calculate how we think about this and get back to a reasonable goal of normality. It’s encouraging that although we [Johnson & Johnson] took a hit for efficacy overall, we are the same globally for reduction of death and disease.”
The 501Y.V2 variant has shown a deft ability to dodge protective antibodies in the bloodstream, which drives up infections in South Africa.
Vaccines developed before the emergence of the variant have shown reduced ability to protect against it.
Bekker says the Novavax and Johnson & Johnson vaccines are the only ones that have “hard and fast” data on the variant. The 501Y.V2 variant is now being reported in 31 countries including the US, UK and Australia.
Hanekom says the Johnson & Johnson (57% efficacy) and Novavax (60%) trials in South Africa suggest less protection against the variant, but there is still some protection, which will have a “massive impact on the pandemic”.
However, he says, published data of these studies are needed to scrutinise the detail to understand what the role of the variant has been.
Hanekom says the clinical results can be complemented with laboratory results and that Pfizer-BioNTech and Moderna have already tested their vaccines against variants and have published results in preprints, which show that the vaccines are sensitive to the variants.
Africa Health Research Institute scientists are using live viruses and plasma samples from trial participants in the Novavax, Johnson & Johnson and Oxford-AstraZeneca studies in South Africa to investigate whether the viruses can be stopped by antibodies generated from the vaccine.
“We are hoping for more definitive results, which are expected soon,” Hanekom said.
Baleta is an independent science journalist, World Health Organisation vaccine safety communications advisor and trainer. She is also a member of the vaccine hesitancy working group of the National Advisory Group on Immunisation
This article was produced by Spotlight – health journalism in the public interest