South Africa has confronted blow after blow to its pandemic-control efforts: A worrisome variant swept throughout the nation, driving a devastating second wave of coronavirus instances. Then officers needed to scramble for another when the vaccine it had wager on, from AstraZeneca, proved ineffective in opposition to the variant, which may partially dodge the physique’s immune system response.

Now the choice — Johnson & Johnson’s single-dose vaccine, the one one now in use in South Africa — has run into hassle as effectively, over concerns of rare blood clots that emerged in a handful of people in the US who had acquired the shot. It is unclear whether the vaccine is responsible.

South Africa’s well being minister, Dr. Zwelini Mkhize, introduced on Tuesday that the nation would briefly halt its vaccine program for medical staff, which has inoculated round 290,000 folks to this point. Dr. Mkhize mentioned he anticipated this system — a medical trial — to renew in just a few days, after the authorities have had an opportunity to look into the blood clot instances in the US.

“Science should be revered always, though this will likely imply a disruption in our plans,” Dr. Mkhize mentioned on Tuesday.

South African well being authorities have been gearing as much as lengthen vaccinations to most people beginning in Might. That program depends on 30 million doses of the Johnson & Johnson vaccine and 30 million of the two-shot Pfizer-BioNTech vaccine, which South African officers not too long ago secured.

The nation halted use of the AstraZeneca vaccine after proof emerged that it didn’t defend clinical-trial individuals from turning into mildly or reasonably sick from the variant, often called B.1.351., that’s now dominant within the nation. South African authorities then pivoted to the Johnson & Johnson vaccine, which is manufactured within the nation beneath license and has a 64 p.c efficacy charge in South Africa, in line with an evaluation by the U.S. Meals and Drug Administration.

Well being specialists say that the choice on Tuesday to pause vaccinating well being care staff is the type of factor that occurs usually in medical trials, and that it most likely gained’t have any main implications for vaccinating most people.

“In the intervening time, there may be nothing to point that it will delay the nationwide rollout program,” mentioned Dr. Richard Lessells, an infectious illnesses specialist on the KwaZulu-Natal Analysis and Innovation Sequencing Platform.

Even so, if proof emerges to implicate the Johnson & Johnson vaccine in blood clotting drawback, and well being officers start to query its security, it might be a devastating blow for South Africa, the African nation hardest hit by the coronavirus, because it races to inoculate its inhabitants earlier than an much more harmful variant seems.

“The U.S. has entry to different vaccines to fill a spot, by way of not utilizing the Johnson & Johnson vaccine,” mentioned Shabir Madhi, a virologist at College of the Witwatersrand who ran the AstraZeneca vaccine trial in South Africa. “That kind of luxurious doesn’t exist in different nations, together with South Africa.”