Could A Single-Dose Of COVID-19 Vaccine After Illness Stretch The Supply?

Mar 1, 2021
Originally published on March 3, 2021 12:38 pm

Public health officials say it's important to vaccinate as many people as quickly as possible to reduce the risk posed by new coronavirus variants. One strategy to stretch existing supplies – albeit with huge logistical challenges — would be to give just one dose of the vaccine to people who have recovered from COVID-19.

About half a dozen small studies, all consistent with one another but as yet unpublished, suggest this strategy could work.

Dr. Mohammad Sajadi, at the University of Maryland medical school's Institute of Human Virology studied health care workers who were just getting their first of two vaccine shots. His research team homed in on those who had previously been diagnosed with COVID-19.

"We saw a much faster response and a much higher response," he says, based on the protective antibodies his team measured in the blood. The infection served the same priming role as an initial dose of the Moderna or Pfizer vaccine would have, so the first shot they got was in effect a booster. It amplified and solidified immunity to COVID-19. The study was published Monday in JAMA, the journal of the American Medical Association.

(The Johnson & Johnson vaccine authorized Saturday by the Food and Drug Administration only requires a single dose.)

So, he says while vaccine is scarce, it makes sense to offer just one shot to people who have already had the disease.

"You can free up automatically millions of doses," he says, increasing vaccine supply by 4% or 5%. "We think it makes sense at this time to promote such a policy."

Federal health officials are intrigued. Dr. Anthony Fauci, who serves as COVID-19 adviser to the White House, has said it's an idea worth further study. (He is dead set against another strategy, which is stretching out the time between first and second doses).

But health officials are not ready to say yes. For one thing, there are still lots of questions, says Allison Aiello, an epidemiologist at the University of North Carolina's Gillings School of Global Public Health.

For one: "Does the vaccination response last as long as it would for somebody who had two vaccines?" she asks. That's not known. Also, the blood tests that measure vaccine effectiveness may not fully indicate whether a person is immune or not.

She and her colleagues conducted one of the studies looking at this issue, and it too found that a single dose stimulated strong immune reactions in 10 people who had recovered from COVID-19. Her study also bears on a practical question, which is how to identify the people who have previously been sick.

One idea is to test for coronavirus antibodies in the blood. But she says those can fade unpredictably, "so using antibody levels would not be a foolproof way of identifying individuals who have had past infection."

And testing for antibodies would add another layer of complexity to a system that's complicated enough as it is.

So, a better strategy might be to focus on the people who have had a positive PCR test to diagnose their disease.

"The trick will be in narrowing in on those 28 million people who have tested positive, communicating with them, and then getting them vaccinated," says Anna Legreid Dopp, senior director of clinical guidelines and quality improvement at the American Society of Health-System Pharmacists.

One question is where to find information about those diagnoses. It's scattered inconveniently in individual medical records, but it has also been collected by state and local health departments, who used it for contact tracing.

"I guess I would see the data coming from more the state level, where it's linking the immunization registries with the state departments of health," she says.

But that could raise legal issues, says Lawrence Gostin, a law professor at Georgetown University. He says that state data are only supposed to be used for public health purposes, and sharing them with, say, a pharmacy that as a vaccine sign-up system is "really stretching the lawfulness and ethics for what you could do." Patients might individually have to give consent to release their data, he says.

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.

"I know it is a little bit wishful thinking," says Legreid Dopp. She's frustrated that there is so much health data out there that could be linked and organized, but systems to do that are often cumbersome or nonexistent.

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. "This is American exceptionalism, and not in a good way," Gostin says.

And adding these complexities could well bog down the struggling vaccination system bog down rather than speed it up.

"With three completely different vaccines going as early as next week, I think that state and local health departments are going to be really taxed on logistics," Claire Hannan, executive director of Association of Immunization Managers, told NPR in an email. "We need to do everything we can to simplify things."

You can contact NPR Science Correspondent Richard Harris at rharris@npr.org.

Copyright 2021 NPR. To see more, visit https://www.npr.org.

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. Transcript provided by NPR, Copyright NPR.