SACHA PFEIFFER, HOST:
South Africa has halted the use of a coronavirus vaccine by AstraZeneca. The country's health minister, Zweli Mkhize, made the announcement on Sunday.
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ZWELI MKHIZE: We have to hold onto AstraZeneca. It is temporary until we figure out these issues. What are the next steps supposed to be? When we know those steps, then, of course, we'll bring it back.
PFEIFFER: The pause comes after a study found the vaccine may not be as effective against a COVID-19 variant that was first detected in South Africa. The country has a million doses of the AstraZeneca vaccine and had planned to deploy them soon. So this setback is a blow to South Africa's pandemic response. So far, the country has recorded more than 1.4 million cases and at least 46,000 deaths. Joining us now is NPR global health correspondent Nurith Aizenman. And, Nurith, ever since these major variants emerged in the U.K., in Brazil, in South Africa, there's been concern that vaccines might not work against them. Is that what's happening in South Africa?
NURITH AIZENMAN, BYLINE: We really don't know yet. But here's why officials there are alarmed. Starting late November, early December, South Africa saw this massive second wave of coronavirus infections fueled by the variant first detected there. It's distinct from the variants first found in the U.K. and Brazil. It's now the dominant strain in South Africa. And it's popping up in many other countries as well, including the U.S. This variant appears to be more transmissible. And it's got some mutations that suggest that existing vaccines could be less effective against it. So South African scientists who were doing a long-running trial of the AstraZeneca vaccine there decided to check. How was it performing against the variant? On Sunday night, the lead researcher, Shabir Madhi, announced in a televised briefing to the nation that the results of the preliminary analysis were troubling.
PFEIFFER: How troubling? What exactly did he find?
AIZENMAN: For this trial, they had given about 2,000 South Africans either the vaccine or a placebo to see over time if those who had gotten the vaccine were less likely to get COVID. The results suggested the vaccine was only about 10% effective at preventing mild or moderate cases of COVID-19 from this new strain.
PFEIFFER: Ten percent, much, much lower than we've heard from some other vaccines. But there are often caveats with studies like this. I understand this one has some.
AIZENMAN: Really, really big caveats. The sample size was tiny, less than 40 COVID cases from the new variant. Also, this finding is just speaking to the vaccine's ability to prevent mild cases. At the briefing, Madhi, the lead scientist, noted that what really matters is whether a vaccine can prevent serious cases, the ones that overwhelm hospitals, cause people to die. And this trial does not shed light on severe cases because only people who were young and quite healthy were studied. Madhi noted that the trials of other vaccines indicate that they are often far more effective at preventing severe cases than mild ones. So he's actually optimistic that the AstraZeneca vaccine will prove useful against severe disease. Company officials have also said they think that's the case.
PFEIFFER: And, Nurith, that sounds very positive, actually. Yet South African officials are already modifying their vaccine strategy based on the not-so-happy news.
AIZENMAN: Right. The government had purchased 1 million doses of the AstraZeneca vaccine. In light of these findings, they've announced that they're going to suspend that effort while they recalibrate. They may decide to just use this vaccine for lower risk populations like young people. Also, AstraZeneca is reportedly already working to adapt the vaccine against this particular variant.
PFEIFFER: What about some of the other major vaccines? Do we know if they will work against this variant?
AIZENMAN: This is a hot question because, of course, this isn't just a problem for South Africa. The variant could become common all over the world. Now, it does appear that another vaccine that's key to many countries' strategy, the Johnson & Johnson one, is at least more effective at preventing mild disease and severe disease than the strain prevalent in South Africa. Madhi, the scientist, said, possibly, they will still need to recalibrate and not aim for achieving herd immunity so fast, but at least use vaccines to protect the most vulnerable from the worst effects of COVID. So this is going to be the vital area of research moving forward.
PFEIFFER: That's NPR's Nurith Aizenman. Thank you.
AIZENMAN: You're welcome. Transcript provided by NPR, Copyright NPR.
