ARI SHAPIRO, HOST:
Public health officials say it's important to vaccinate as many people as quickly as possible to reduce the risk from new coronavirus variants. One strategy to stretch existing supplies would be to give just one dose of the vaccine to people who've recovered from COVID-19. But NPR science correspondent Richard Harris reports the logistics of doing that are daunting.
RICHARD HARRIS, BYLINE: Dr. Mohammad Sajadi at the University of Maryland's Institute of Human Virology was interested to see how people who had recovered from COVID-19 responded after just the first shot of a two-dose vaccine.
MOHAMMAD SAJADI: We saw a much faster response and a higher response earlier.
HARRIS: And how equivalent is that then to essentially having a booster shot after a vaccine?
SAJADI: It - well, that's exactly what this is, right?
HARRIS: He and his colleagues report today in JAMA that the initial infection was equivalent to the first shot of a vaccine. His lab and about half a dozen others have seen that this response is at least as good, if not better, than someone who gets two vaccine doses. These studies, though mostly unpublished, together make a strong case. So he says while vaccine is scarce, why not just offer one shot to people who have already had the disease?
SAJADI: You could free up automatically millions of doses and about, I would say, 4- to 5% increase in the vaccine supply automatically. We think it makes sense at this time to promote such a policy.
HARRIS: Federal health officials are intrigued, but are hesitant to go this route. For one thing, there's still lots of questions, says Allison Aiello, an epidemiologist at the University of North Carolina.
ALLISON AIELLO: Does the vaccination response last as long as it would for somebody who had two vaccines?
HARRIS: Her own studies of this topic also bear on a practical question, which is how to identify the people who have previously been sick. One idea is to test for antibodies in the blood, but she found that those can fade unpredictably.
AIELLO: So using antibody levels would not be a foolproof way of identifying individuals that have had past infection.
HARRIS: And testing for antibodies would add another layer of complexity to a system that's complicated enough as it is. So Anna Legreid Dopp at the American Society of Health-System Pharmacists says a better strategy might be to focus on people who have had a positive PCR test.
ANNA LEGREID DOPP: The trick will be in narrowing in on those 28 million people who have tested positive, communicating with them and then getting them vaccinated.
HARRIS: The question is where to find information about those diagnoses. It's scattered in individual medical records, but it has also been collected by state and local health departments who used it for contact tracing.
LEGREID DOPP: I guess I would see the data coming from more at the state level, where it's the linking of the immunization registries with the state departments of health.
HARRIS: But that could raise legal issues because that state data is only supposed to be used for public health purposes, and it's not clear whether it can be shared with, say, a pharmacy without each patient's explicit permission. What's more, these databases aren't currently configured for that purpose, and it could take many months to do that, by which time vaccines may no longer be in short supply.
LEGREID DOPP: I know it is a little bit wishful thinking.
HARRIS: This strategy could make sense in countries like England and Israel, which have strong centralized health systems. But the U.S. system just isn't set up that way. And adding these complexities could well make the struggling vaccination system bog down instead of speed up.
Richard Harris, NPR News.
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