South Africa is suspending the deployment of AstraZeneca's (AZN  ) coronavirus vaccine after it was discovered that the vaccine was less effective against the recently discovered variant spreading throughout the country.

The South African Department of Health announced its decision to suspend the vaccine rollout on Sunday. Minister of Health Dr. Zweli Mkhize said that the temporary hold was being enacted to give the government time to reconsider its vaccine rollout. The decision was influenced by a recently released report by the University of Witwatersrand, which found that the vaccine barely offered any protection against mild cases of COVID-19.

"Vaccines that are effective against the more severe forms of disease may not affect milder forms, so there is optimism that severe disease will still be prevented by vaccines," said Peter Openshaw of the Imperial College London, quoted by the Associated Press.

The study's findings aren't quite "official" or definitive quite yet, having not been peer reviewed yet (though the study has since been submitted to other universities for review and should be released to the public shortly thereafter). The study also only covered younger demographics that are at less risk of contracting a severe case of COVID-19. There's still hope that the vaccine will be effective against severe cases. Some health experts and AstraZeneca voicing their belief that the vaccine could still be effective in reducing strain on hospitals by reducing the volume of severe cases.

AstraZeneca's shares seem to have taken a bit of a hit from the news, though the company still managed to reach $50.06 before markets closed on Monday, 0.69% up from Friday's closing price of 49.72. The slight drop during Monday trading may have been unrelated to the events in South Africa; a quick look at AstraZeneca's performance over the last few months shows a great deal of fluctuation, bouncing between a high of $58.02 and a low of $48.52 over the last six months to date.