Efficacy of a coronavirus vaccine from Sinovac – one of main jabs – has been found to be as low as 50.4 percent.
The coronavirus variant discovered in South Africa can “break through” Pfizer-BioNTech’s COVID-19 vaccine to some extent, a study in Israel found.
The South African coronavirus variant managed to penetrate the protection offered by two doses of the Pfizer-BioNTech vaccine to some degree, though it remains unclear just how much efficacy is lost, it said.
The research, released on Saturday, compared nearly 400 people who tested positive for COVID-19 two weeks or more after they received one or two doses of the vaccine, against the same number of unvaccinated patients with the disease.
It matched age and gender, among other characteristics.
The South African variant, B.1.351, was found to make up about 1 percent of all the COVID-19 cases across all the people studied, according to the study by Tel Aviv University and Israel’s largest healthcare provider, Clalit.
But among patients who had received two doses of the vaccine, the variant’s prevalence rate was eight times higher than those unvaccinated – 5.4 percent versus 0.7 percent.
This suggests the vaccine is less effective against the South African variant, compared with the original coronavirus and a variant first identified in Britain that has come to comprise nearly all COVID-19 cases in Israel, the researchers said.
“We found a disproportionately higher rate of the South African variant among people vaccinated with a second dose, compared with the unvaccinated group. This means that the South African variant is able, to some extent, to break through the vaccine’s protection,” said Tel Aviv University’s Adi Stern who led the study.
However, the researchers cautioned that the study only had a small sample size of people infected with the South African variant because of its rarity in Israel.
They also said the research was not intended to deduce overall vaccine effectiveness against any variant, since it only looked at people who had already tested positive for COVID-19, not at overall infection rates.
Pfizer and BioNTech could not be immediately reached for comment outside business hours.
The companies said on April 1 that their vaccine was about 91-percent effective at preventing COVID-19, citing updated trial data that included participants inoculated for up to six months.
With respect to the South African variant, they said among a group of 800 study volunteers in South Africa, where B.1.351 is widespread, there were nine cases of COVID-19, all of which occurred among participants who got the placebo.
Of those nine cases, six were individuals infected with the South African variant.
The Israeli researchers said they have been testing a third dose of their shot as a booster, and have said they could modify the jab to specifically address new variants if needed.
Some previous studies have indicated the Pfizer-BioNTech shot was less potent against the B.1.351 variant than against others of the coronavirus, but still offered a robust defence.
While the results of the study may cause concern, the low prevalence of the South African strain was encouraging, according to Stern.
“Even if the South African variant does break through the vaccine’s protection, it has not spread widely through the population,” said Stern, adding the British variant may be “blocking” the spread of the South African strain.
Almost 53 percent of Israel’s 9.3 million population has received both doses of the Pfizer-BioNTech vaccine.
Israel has largely reopened its economy in recent weeks as the pandemic appeared to recede, with infection rates, severe illness and hospitalisations dropping sharply.
About one-third of Israelis are below the age of 16, which means they are still not eligible for the shot.