Omicron response to vaccines analyzed in new study from South Africa : Goats and Soda Data from 78,000 South Africans with COVID show the Pfizer vaccine is far less effective in preventing infection by the omicron variant. But there is still significant protection from severe illness.

Vaccine protection vs. omicron infection may drop to 30% but does cut severe disease

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MARY LOUISE KELLY, HOST:

To another story now - as predicted, the omicron variant of the coronavirus is rapidly gaining a foothold here in the U.S. The CDC said today its prevalence has likely jumped more than tenfold in just two weeks. Omicron could be to blame for 13% of cases now in a region that includes New York and New Jersey. Meanwhile, omicron's already surging in South Africa, and scientists there are getting new insights into how it behaves. NPR's global health correspondent Michaeleen Doucleff is here.

Hey there.

MICHAELEEN DOUCLEFF, BYLINE: Hi.

KELLY: Hi. So let's start with what we're learning from South Africa. A study from there looked at how well two doses of the Pfizer vaccine worked against omicron. What did it find?

DOUCLEFF: Yeah. Well, there's some bad news in the study, and there is some good news. So the study comes from a large private health insurance company called Discovery Health, and scientists there analyzed health records from more than 200,000 people who tested positive for COVID over the past several months. And here's the bad news. They found that protection against infection drops dramatically for omicron, down to about 30%. So if you compare that to delta, the vaccine offered 80% protection against that variant in this study.

KELLY: Thirty percent, you said, against...

DOUCLEFF: Yeah.

KELLY: ...Infection? And that's if you've had two doses of Pfizer. Wow. That sounds really not good. You said there is some good news? What's the good news from this study?

DOUCLEFF: Yeah. So last week, we were talking about a few lab studies that hinted that the vaccines would still protect against severe disease. And now, we have real-world data showing just that. The new study found that just two doses of the Pfizer vaccine reduced a person's risk of hospitalization due to omicron by 70%.

Dr. Ryan Noach is the CEO at Discovery Health. He helped lead the study. He said, like with delta, it's the unvaccinated people that are ending up in the hospitals.

RYAN NOACH: What is clear is that vaccinated individuals are experiencing milder infections in general, and it's primarily the unvaccinated that are requiring admission and also that are requiring oxygen (unintelligible).

DOUCLEFF: So also what's good news is this protection against severe disease is seen in older people as well as people with higher risks.

KELLY: OK. So explain a little bit more. We keep hearing omicron is really, really contagious, but that maybe it makes you less sick than other variants, causes a milder illness. Does the study hit that point?

DOUCLEFF: Yes, it did. But it's a little tricky data. So the data suggests there are fewer hospitalizations. People who do end up in the hospital require less intensive care. And in general, people recover more quickly with this variant. So for instance, a mild course often resolves within just three days.

KELLY: Which would not be terrible - three days.

DOUCLEFF: No, not at all. But here's the tricky part. The researchers point out that this data does not mean that omicron is less virulent in general, that it will cause less severe disease in every country, including here in the U.S.

KELLY: Why - hold on. Why would it cause less severe disease in South Africa, but not everywhere?

DOUCLEFF: Yeah. So it has to do with the - with exposure to the virus. The majority of people in South Africa - we're talking about, like, 80% of people - have already been infected with COVID before omicron came. Some people have even been infected two times before. And every time you're exposed to the virus, whether it's an infection or the vaccine, your immunity improves. And if you catch COVID again, your symptoms are more likely to be mild.

KELLY: Ah. So you're saying the data shows that omicron is - looks less severe in South Africa, but that's because many of the people getting infected in South Africa have already had COVID, so they have some immunity?

DOUCLEFF: Exactly right. The exposure rate isn't as high here, so we're going to have to just wait and see if omicron will be - will cause milder disease here, too.

KELLY: Ugh. All right. NPR's global health correspondent Michaeleen Doucleff with some mixed news there.

Thanks, Michaeleen.

DOUCLEFF: Thank you, Mary Louise.

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