The coronavirus variant discovered in South Africa can break through the protection provided by Pfizer Inc and BioNTech’s COVID-19 vaccine to some extent, a real-world data study in Israel found. However, the variant’s prevalence in Israel is very low and the vaccine remains highly effective.
The study was released on the medRxiv pre-print site on April 9 and has not been peer reviewed. It compared almost 400 people who had tested positive for COVID-19, 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% 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% versus 0.7%.
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.
The researchers said the study was not intended to assess 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.
Separate real-world Israeli studies on the vaccine’s overall effectiveness, including by Clalit, have shown the Pfizer shot to be more than 90% effective. L1N2KU3L6
“We found a disproportionately higher rate of the South African variant among people vaccinated with a second dose, compared to 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.
In an update to the study posted on April 16, the researchers noted that within the group of people who received two doses, which comprised eight people, all of the B.1.351 infections occurred within a week to 13 days after the second shot. None of them tested positive for it 14 days or more after the second dose.
“This may imply that there is a short window of susceptibility to B.1.351 infection limited to the immediate two weeks after the second dose – but we cannot be confident that this is indeed the case,” Stern and Clalit’s Ran Balicer said in an email to Reuters on Sunday.
The researchers cautioned, though, that the study only had a small sample size of people infected with the South African variant because of its rarity in Israel.
“The B.1.351 incidence in Israel to-date remains low and vaccine effectiveness remains high among those fully vaccinated,” the study said.