South Africa’s health products regulator on Monday said that it would not approve Russia’s Sputnik V COVID-19 vaccine as it could increase the risk of HIV infection among men.

The decision was based on earlier studies which tested the safety of a modified form of adenovirus a type of virus that causes respiratory infections, known as the Ad5 and contained in the Russian jab. 

“Use of the Sputnik V vaccine in South Africa, a setting of a high HIV prevalence and incidence, may increase the risk of vaccinated males acquiring HIV,” the South African Health Product Regulatory Authority (SAHPRA) said in a statement.

It further noted that the company behind the application for the use of Sputnik V in South Africa had no proof that the formula would be safe “in settings of high HIV prevalence”.

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“The rolling review of the Sputnik V vaccine will, however, remain open for submission of relevant safety data in support of the application,” it added.

Russia’s Gamaleya Centre, which developed Sputnik V, said it would produce information to show that SAHPRA’s concerns were “completely unfounded”. “Speculation regarding the association between adenovirus type-5 vectored vaccines and HIV transmission in high risk groups has been based on small-scale studies,” it said in a statement.   

This week, South Africa is set to begin vaccinating children as young as 12 as they are now offering booster shots to certain immuno-compromised citizens.

South Africa is currently offering the single-dose Johnson & Johnson, which also contains an adenovirus but of a different type, and the rMNA Pfizer/BioNTech jab. Sinovac has also been approved.