Covid-19 Survivors Might Only Need One mRNA Vaccine Dose

Covid-19 Survivors Might Only Need One mRNA Vaccine Dose
Frozen vials of the Pfizer/BioNTech vaccine being thawed out for use at a hospital in Belgium (Photo: Francisco Seco, AP)

For people who have survived a past encounter with covid-19, only one dose of a mRNA vaccine may be needed for full protection, research released Wednesday suggests. The findings add weight to the proposed idea by some experts that survivors should only get one shot in order to help stretch out the vaccine supply.

Researchers at Mount Sinai have been studying the ins-and-outs of immunity to the coronavirus since the start of the pandemic. Their earlier work, for instance, has suggested that natural immunity from infection tends to be robust and lasts for at least six months in most survivors. It’s still an area of active research, though, and reinfection is possible. And many who have survived covid-19 would be at higher risk for serious illness if they were unlikely enough to catch it and become sick again. Both doctors and the Centres for Disease Control and Prevention still recommend that everyone eligible for vaccination should receive it, even if they’ve endured covid-19 already.

While the rollout of vaccinations has been improving steadily since last December, only around 19% of the U.S. has received at least one dose, and less than 10% have been fully vaccinated. In hopes of speeding up vaccination efforts, some scientists have argued that covid-19 survivors should be told to only get one dose of the similar Moderna and Pfizer/BioNTech vaccines. Until recently, they were the only available vaccines in the country. Yet other experts have cautioned that we still don’t know whether these people would be as fully protected as everyone else who gets the standard two-dose course.

To help settle this question, the researchers at Mount Sinai looked at 109 previously uninfected volunteers who had either been fully vaccinated or were survivors (confirmed through antibody testing) who at the time had only gotten one dose of either mRNA vaccine. In another group of 231 people, they compared the level of reported side effects between survivors and uninfected people post-vaccination.

The study, published in the New England Journal of Medicine, found that survivors given one dose had a similar and often greater antibody response to the coronavirus than those fully vaccinated. Survivors also tended to experience side effects like infection site pain or fatigue more often after the first dose, compared to uninfected people after the first dose, but at levels that were similar to people after they had received the full two doses. Since these side effects are usually a sign of the body’s immune system learning how to recognise the virus, that too suggests survivors who get only one shot are still getting as much protection from covid-19 as everyone else who gets two doses.

“For that reason, we believe that a single dose of vaccine is sufficient for people who have already been infected by SARS-CoV-2 to reach immunity.”said study author Viviana Simon, a professor in the Departments of Microbiology and Medicine at Mount Sinai’s Icahn School of Medicine, in a statement released by the university.

The study’s findings were originally released to the public early last month as a preliminary paper on the website medRxiv. At the time, they were notable enough for the director of the National Institutes of Health, Francis Collins, to write about them. Though Collins did discuss the study, which was NIH-funded, favourably, he also pointed out that it would take seeing other studies supporting the same conclusion before there would likely be any official change in guidance from the Food and Drug Administration or CDC. The new study doesn’t weigh in on Johnson & Johnson’s one-shot vaccine that uses a different technology to increase covid-19 immunity, and what it could mean for covid-19 survivors.

If that data does show up, it could very well go a long way in extending our vaccine supply. No one is really sure yet, but anywhere from 20% to 30% of the country has already had covid-19. And though vaccine access is getting better, any little boost in speed would help out greatly.