Had Covid? You May Need Only One Dose of Vaccine, Study Suggests

Had Covid? You May Need Only One Dose of Vaccine, Study Suggests

People who have already been sick with Covid-19 should still be vaccinated, experts say, but they may experience intense side effects even after one dose.

Shannon Romano, a molecular biologist, came down with Covid late last March, about a week after she and her colleagues shut down their lab at Mount Sinai Hospital. A debilitating headache came first, followed by a fever that kept rising, and then excruciating body aches. “I couldn’t sleep. I couldn’t move,” she said. “Every one of my joints just hurt inside.”

It was not an experience she wanted to repeat — ever. So when she became eligible for the Covid-19 vaccine earlier this month, she got the shot.

Two days after her injection, she developed symptoms that felt very familiar. “The way my head hurt and the way my body ached was the same headache and body ache I had when I had Covid,” she said. She recovered quickly, but her body’s intense response to the jab caught her by surprise.

A new study may explain why Dr. Romano and many others who have had Covid report these unexpectedly intense reactions to the first shot of a vaccine. In a study posted online on Monday, researchers found that people who had previously been infected with the virus reported fatigue, headache, chills, fever, and muscle and joint pain after the first shot more frequently than did those who had never been infected. Covid survivors also had far higher antibody levels after both the first and second doses of the vaccine.

A dose of Pfizer’s vaccine was prepared at a vaccination site in Rohnert Park, Calif.

Had Covid? You May Need Only One Dose of Vaccine, Study Suggests

Based on these results, the researchers say, people who have had Covid-19 may need only one shot.

“I think one vaccination should be sufficient,” said Florian Krammer, a virologist at the Icahn School of Medicine at Mount Sinai and an author on the study. “This would also spare individuals from unnecessary pain when getting the second dose and it would free up additional vaccine doses.”

A second study released on Monday bolsters the idea. The research included 59 health care workers, 42 of whom previously had Covid (with or without symptoms). The researchers didn’t assess side effects, but they did find that those who had been previously infected responded to the first jab by generating high antibody levels, comparable to the amounts seen after the second dose in people who had never been infected. And in lab experiments, those antibodies bound to the virus and stopped it from entering cells. To stretch the vaccine supply, the authors conclude that those who have previously had Covid should be moved down the priority list and receive only one dose of the vaccine while supplies are limited.

While some scientists agree with this logic, others are more cautious. Changing the number of doses could create “a really tricky precedent,” said E. John Wherry, director of the University of Pennsylvania’s Institute for Immunology. “We don’t take FDA approvals of, say, a chemotherapeutic drug and then just throw out the dosage schedule,” he said.

Dr. Wherry also pointed out that people who had mild cases of Covid seem to have lower antibody levels, and may not have protection against more contagious variants of the virus. It might also be difficult to identify which people have previously been infected. “Documenting that becomes a really potentially messy public health issue,” he said.