One shot of vaccine may be enough for COVID-19 survivors, studies suggest

For people who have bared their arms for a twodose COVID-19 vaccine, the message from public health officials has been clear: Get the second shot if you want full protection.

But emerging evidence suggests there may be an exception to that rule. If you have already battled a coronavirus infection, it’s possible one dose may suffice.

“This has been rumored for a long time, that people with preexisting disease need only a single dose to get really long-lasting immunity,” said Dr. George Rutherford, an infectious disease epidemiologist at UC San Francisco.

Both the Pfizer-BioNTech and Moderna vaccines require two doses given a few weeks apart. The first dose essentially primes the immune system to recognize and attack the virus’s telltale spike protein, while the second one prompts a flood of antibodies.

Getting that second dose is essential in order to get the fullest possible protection against the virus, experts say.

There are a few exceptions to the two-dose rule — such as having an immediate or severe allergic reaction to the first dose — but, so far, being a COVID-19 survivor isn’t one of them.

However, researchers are increasingly finding that a SARS-CoV-2 infection may act a lot like the first shot of the vaccine.

A study by scientists in Seattle and Montreal examined blood serum samples from people who had recovered from COVID-19 and from others who had never had a coronavirus infection. Samples were collected both before and after immunization with either the Pfizer or the Moderna vaccine.

The researchers found that, in the COVID-19 survivors, a single dose of vaccine boosted antibody levels against several different coronavirus variants by up to a thousandfold — and that a second dose essentially offered no additional benefit. Meanwhile, those with no history of infection had lower antibody levels after two doses of vaccine than previously infected people had after just one. Those findings were reported last month in the journal “Science.”

In another recent study, researchers in New York looked at serum samples from 110 people, some who had been infected with SARS-CoV-2 and some who had not, and analyzed how their antibody levels differed after getting the Pfizer or the Moderna vaccine.

They found that, after just one shot, those who had already been infected had antibody levels 10 to 45 times higher than those whose histories were infection-free. Moreover, with just that first dose, the COVID-19 survivors’ median antibody levels were more than six times higher than levels in uninfected folks who completed the two-dose regimen, according to the report in the New England Journal of Medicine.

A preliminary version of those findings prompted Dr.

Francis Collins, director of the National Institutes of Health, to observe that “the results raise the possibility that one dose might be enough for someone who’s been infected with SARSCoV-2 and already generated antibodies against the virus.” However, he added in a blog post, “much more research is needed — and I am definitely not suggesting a change in the current recommendations right now.”

The New York scientists also found that people who had previously been infected tended to have more symptoms after their first shot compared with their never-infected peers. They were also more likely to report other less common vaccine side effects, including headache, fatigue, fever, chills, muscle aches and joint pain.

France’s health authority has already issued a recommendation that those who had a confirmed SARSCoV-2 infection take just one dose of vaccine, even if their infection didn’t result in symptoms of COVID-19.

Collins suggested the U.S. Food and Drug Administration might follow suit if the evidence continues to build. Such a policy could help extend vaccine supply and get more people immunized more quickly, he wrote.