South Africa has temporarily suspended the rollout of Johnson & Johnson’s COVID-19 vaccine.

The Minister of health DR Zweli Mkhize recommended pausing its use because of rare cases of blood clots.

The U.S. Food and Drug Administration (FDA) said the pause there was expected to be a matter of days. Six women under age 50 developed rare blood clots in the United States among more than 6 million people given the J&J shot so far.

“I had urgent consultations with our scientists, who advised that we cannot take the decision by the FDA lightly. Based on their advice, we have determined to voluntarily suspend our rollout until the causal relationship between the development of clots and the Johnson & Johnson vaccine is sufficiently interrogated,” Health Minister Zweli Mkhize told reporters.

However, Mkhize said there had not been reports of such clots in South Africa after almost 290,000 vaccinations.

In South Africa, the J&J vaccine has been given to health workers in a research study that is further testing it in the field.

The government expects to receive its first batch of commercial doses later this month, as part of a bilateral deal with J&J for 31 million doses.

South Africa is the worst-hit country on the African continent in terms of recorded coronavirus infections and deaths. It suffered a severe “second wave” of infections that was driven by a more infectious virus variant called 501Y.V2.