South Africa’s health products regulator has turned down approval for Russia’s Covid vaccine Sputnik V for use.

This is due to two failed research studies testing an HIV vaccine also using Adenovirus Type 5, which found men given Sputnik had a higher risk of being infected with HIV. The regulators said they had asked the Russian makers of Sputnik V to provide data proving the vaccine’s safety in a country with high rates of HIV but that “the applicant was not able to adequately address (their) request.”

Widespread vaccine hesitancy in Russia has seen only 32% of the population vaccinated despite availability of Sputnik V prompting Vladimir Putin to grant all Russians a week off work in an attempt to reverse the dramatic increase in COVID deaths this month.

Sputnik V is yet to be authorized by the World Health Organization and the European Medicines Agency however, the shot has been given the green light in more than 70 countries with no significant safety problems identified.

In a statement, the Gamaleya Centre, manufacturers of Sputnik called the concerns about the vaccine’s vector “completely unfounded.” It said speculation about the link between Adenovirus Type 5 and HIV transmission in high-risk populations was based on “small-scale inconclusive studies among volunteers with highly probable risky behaviour.” It noted that the same vector was used in China’s CanSino vaccine, which has been widely used in China.

Dr. Julian Tang, a virologist at Britain’s University of Leicester, was perplexed by the South African decision to reject Sputnik V. “It’s a strange connection to make,” he said, explaining that while past concerns have been raised about using the particular virus vector in Sputnik V, much remains uncertain. “It’s not the vector that caused HIV so you can’t just blame it on that,” Tang said.

The widely accepted AstraZeneca vaccine uses a related chimpanzee adenovirus; both it and the Johnson & Johnson shot have been approved in South Africa.