More than two months after being fully vaccinated against Covid, a doctor in New York woke up with a headache and a feeling of dull and heavy tiredness. A fever and chills soon followed, and his sense of taste and smell began to fade.
This, he thought, could not be happening. But it was: he tested positive for the coronavirus.
“It was a huge shock,” he said. He knew that no vaccine was perfect and that the injections from Pfizer-BioNTech he received were considered 95 percent effective in a large clinical trial. “But somehow, in my mind, it was 100 percent,” he said.
The doctor, who asked to remain anonymous to protect his privacy, is among the few reported cases of people who became infected after being partially or fully vaccinated. Nearly 83 million Americans have received at least one dose of the Covid vaccine, and it is unclear how many of them will have a “discovered” infection, although two new reports suggest that the number is very small.
One study found that only four of the 8,121 fully vaccinated employees at Southwestern Medical Center in Dallas were infected. The other found that only seven of the 14,990 workers at UC San Diego Health and the David Geffen School of Medicine at the University of California, Los Angeles tested positive two or more weeks after receiving a second dose of the Pfizer-BioNTech or Moderna vaccines. Both reports, published Tuesday in the New England Journal of Medicine, show how vaccines work in the real world, and during a period of intense transmission.
But these groundbreaking cases, while quite rare, are a clear reminder that vaccinated people are not invincible, especially when the virus continues to circulate widely.
“We felt very strongly that this data should not cause people to say, ‘We are all going to be vaccinated and then we can all stop wearing masks,’” said Dr. Francesca J. Torriani, an infectious disease specialist at UC San Diego Health who led the California study. “These measures should continue until a larger segment of the population is vaccinated.”
Only a few of the positive Covid health workers in the California study showed symptoms, she said, and they tended to be mild, suggesting that the vaccines were protective. This echoes vaccine test data, indicating that invasive infections were mild and did not require hospitalizations. Some people did not show any symptoms and were discovered only through tests in studies or as part of their medical care.
For example, doctors at the University of North Carolina found some asymptomatic cases in vaccinated patients who were tested for coronavirus before surgery or other medical procedures, according to Dr. David Wohl, the medical director of the vaccine clinic at that center .
He said the absence of symptoms could have meant that the vaccine was doing exactly what it was supposed to do: prevent people from getting sick, even if it didn’t completely block the virus from infecting them.
The Center for Disease Control and Prevention has a small team that studies innovative cases, said agency spokeswoman Kristen Nordlund. One question the researchers are considering is whether certain variants of the coronavirus may play a role in the discovery cases.
“Currently, there is no evidence that Covid-19 after vaccination is occurring because of changes in the virus,” said Nordlund.
In the coming months, Pfizer and Moderna are expected to release data that should indicate how often vaccinated people are infected with the virus, even if they have no symptoms. The companies have tested participants in their vaccine tests for antibodies to a protein called N, which is part of the coronavirus, but not part of the vaccine. Finding these antibodies means that a vaccinated person has been infected with the virus. Some study volunteers are also having their noses cleaned regularly to test for an active viral infection.
Another issue is the effectiveness of vaccines in people whose immune systems have been weakened by disease or medication, said Dr. William Schaffner, an infectious disease specialist at Vanderbilt University. Innovative cases can occur in these people because their bodies cannot produce a robust reaction to a vaccine.
“And it’s amazing how widespread immunocompromise is,” said Dr. Schaffner. He called the disease “a testament to modern medicine” because many patients with it are being successfully treated for illnesses that would not have killed them long ago.
The doctor who fell ill in New York despite the full vaccination was isolated at home for almost two weeks. He described his illness as relatively mild and said he was treated with monoclonal antibodies to fight the virus. “If the worst flu is 10, this is four,” he said.
Without the vaccine, he said, he believes he would have been sicker.
“I would have feared for my mortality,” he said. “But I didn’t have an anxious moment. I didn’t think I was going to die. To think that you are not going to die – that’s a big deal. “
Apoorva Mandavilli contributed reporting.