With COVID-19 case trends taking troublesome turns after weeks of steady declines, health experts worry the handful of more contagious coronavirus variants spreading in the U.S. may outpace vaccination efforts.
Earlier debates centered around delaying second doses for the Pfizer-BioNTech and Moderna shots in an attempt to inoculate more people in a shorter period — a move that some believe could save more lives in the long run.
Now, mounting evidence suggests people who have recovered from COVID-19 could harmlessly skip their second dose altogether, potentially freeing up millions of vaccines for others who have not been infected and are thus more vulnerable to developing severe disease.
Researchers behind new studies, mostly non-peer reviewed, have found that recovered COVID-19 patients develop far higher levels of coronavirus antibodies after just one dose of a two-dose series vaccine than people who have never been infected. Other research has shown that second doses of a COVID-19 vaccine in recovered patients were virtually useless — other than serving as a booster to already superb immunity — after antibody levels neither jumped nor dropped.
But telling the nearly 30 million people in the U.S. who have been infected with the coronavirus to forget everything they were told and skip their second dose is more complicated than it seems, experts say.
“What these data show is exactly what you’d expect — that people who’ve been naturally infected, who already had developed an immune response to this virus, when they’re then given that quote unquote first dose have a booster response,” Dr. Paul Offit, director of the Vaccine Education Center at the Children’s Hospital of Philadelphia, told CNN last week. “In other words, they’re acting as if they’re getting the second dose.”
“You could reasonably ask, ‘Well, given that there’s a shortage of vaccine, why not make this recommendation that anyone who’s been previously infected can reasonably get one dose, period?’ I think the reason that that didn’t happen was largely programmatic,” Offit added.
For starters, health care workers would need to take the additional step of screening people for past infection, such as with a blood test. A change could also add confusion over public health messaging on COVID-19 vaccination, experts say.
Another complicating factor is that scientists don’t know how immunity from one dose of a vaccine in recovered COVID-19 patients compares to immunity from two doses in an uninfected person over time. They also don’t know how long natural immunity — protection gained from infection alone — lasts.
That’s why the Centers for Disease Control and Prevention says people who have had COVID-19 should still get vaccinated, especially as variants that have been shown to evade vaccines to small degrees continue to spread in the U.S.
Recovered COVID-19 patients have ‘massive boost’ in immunity after one dose
One of the more recent studies found that a group of 59 health care workers in Maryland with a previous coronavirus infection had higher levels of antibodies after a single dose of either the Pfizer or Moderna vaccine than those without a history of infection. The researchers of the study published March 1 in the journal JAMA said their results support lowering recovered COVID-19 patients on vaccination priority lists or giving them just one dose of a two-dose vaccine series.
Study co-author Dr. Mohammad Sajadi, of the University of Maryland medical school’s Institute of Human Virology, told NPR that a single-dose strategy for patients with previous COVID-19 infection could “free up automatically millions of doses,” which could increase vaccine supply by 4% or 5%.
And now that the Johnson & Johnson vaccine, which requires a single dose, has been authorized for emergency use in the U.S., experts expect supplies to gradually increase anyway.
A separate study in London found that health care workers who did not previously have COVID-19 gained “comparable” levels of antibodies after their first dose of the Pfizer shot to those in recovered COVID-19 patients who had not been vaccinated — evidence that protection from natural immunity is on par with a single vaccine dose.
And among those with a previous infection, their antibody levels jumped more than 140-fold after one dose.
Another non-peer reviewed paper posted in early February found that one dose of the Pfizer or Moderna shot increased the amount of antibodies in the blood of people who previously had COVID-19 a 1,000-fold against the original coronavirus stain, the one from South Africa and even the coronavirus that caused the SARS epidemic in 2003.
That’s “a massive, massive boost… It looks pretty clear that we’re boosting their pre-existing immunity,” Dr. Andrew McGuire, an immunologist at the Fred Hutchinson Cancer Research Center in Seattle who led the study, told The New York Times. Although researchers don’t know how long the high levels of antibodies will last, McGuire said “hopefully, they’ll last a long time.”
Yet another study found that antibody levels in people who previously had COVID-19 showed “muted responses” to their second dose of the Pfizer vaccine, suggesting one dose may be enough to protect them from severe disease.
Health officials in the U.S. have not formally addressed skipping second doses for those who have recovered from the coronavirus, but research shows completing the vaccination series doesn’t hurt.
“If you’ve never been infected with this virus before, that second dose of mRNA vaccine dramatically boosts your T-cell immunity, dramatically boosts your antibody response and will no doubt give more complete and longer-lived protection,” Offit of the Children’s Hospital of Philadelphia told CNN.