Two reports of so-called breakthrough coronavirus infections – in which fully vaccinated individuals contract the disease – suggest that the vaccines still provide strong protection against serious diseases, even in variants.
The cases, described Wednesday in the New England Journal of Medicine, involved two of more than 400 fully vaccinated study participants who were tested weekly for Covid-19. Both women developed mild cases of the disease and recovered quickly.
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The study’s co-author, Dr. Robert Darnell, a professor and senior physician at Rockefeller University in New York City, said the two cases are no cause for alarm.
“They certainly did not need to be hospitalized,” he said. “They had cases of Covid-19 at home.”
As the number of fully vaccinated individuals in the United States increases, so will the reports of breakthrough infections. Last Friday, the Centers for Disease Control and Prevention said it had received reports of about 5,800 breakthrough infections in more than 77 million fully vaccinated people.
Breakthrough infections can occur because no vaccine is 100 percent effective. Yet such cases remain very rare.
CDC officials are collecting more data on breakthrough cases to determine if patterns exist in patients. One of the questions the agency asks is whether certain variants are more likely to play a role in breakthrough cases.
Both cases in the New England Journal of Medicine report were sequenced, and both cases were found to share certain mutations with the variants first identified in the United Kingdom and New York. However, neither contained all mutations corresponding to these previously identified variants. (Variants of the virus can contain a number of mutations.)
Nonetheless, experts warned that because the report included only two cases, it is too early to draw any conclusions about which variants are most likely to lead to breakthrough infections.
One of the samples contained a mutation called E484K, which is also found in the variants from South Africa, Brazil, and New York City, and is believed to help the virus bypass the body’s immune response to some degree.
Jeremy Kamil, a virologist at LSU Health Shreveport, said he was not surprised this mutation was detected, as lab data suggests it could play a role in breakthrough cases.
“If you asked scientists what mutations you would expect in a breakthrough infection, I think the first answer you would get would be E484K,” said Kamil, who was not involved in the new research.
Also Wednesday, two studies published in the CDC’s Weekly Morbidity and Mortality Report, related to breakthrough infections in nursing homes. One report identified 22 breakthrough infections in 78 nursing homes in the Chicago area, which from December to March had fully vaccinated nearly 15,000 residents and staffers. In two-thirds of the breakthrough cases, the infections were asymptomatic, although several people developed mild to moderate symptoms, the report said. Two patients were hospitalized and one person died.
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The second report focused on an outbreak of Covid-19 at a Kentucky nursing home in March. Twenty-six residents and 20 executives tested positive, including 18 residents and four executives who were fully vaccinated. Sequencing the cases detected the same E484K mutation as in the New York cases.
However, those vaccinated were still 87 percent less likely to develop symptoms compared to those who were not vaccinated.
“The results of this study are telling that vaccination resulted in a reduced risk of infection and symptomatic disease in a high-risk population,” such as a nursing home, said Jason Kindrachuk, an assistant professor of medical microbiology and infectious diseases at the University of Manitoba. . in Winnipeg.
Likewise, the women described in the New England Journal of Medicine report also had mild symptoms, said Kindrachuk, who was not involved in the new reports. “The vaccines did exactly what we assumed based on clinical trial data and real world data: they protected against serious disease.”
One of the patients in the New England Journal of Medicine report, a healthy 51-year-old woman, tested positive for Covid-19 on March 10, 19 days after her second dose of the Moderna vaccine. She said she followed guidelines, which included masking and social distancing, but developed symptoms such as sore throat, congestion, and headaches. The day after her test, she lost her sense of smell. All her symptoms disappeared a week later.
The second patient, a 65-year-old woman with no risk factors for severe Covid-19, tested positive on March 17, 36 days after her second dose of the Pfizer-BioNTech vaccine. She fell ill two weeks after her unvaccinated partner was diagnosed with Covid-19.
Her symptoms included fatigue, blocked sinuses and headaches. As in the first case, her symptoms disappeared after just a few days.
While data from the CDC suggests breakthrough infections are rare, Darnell said it would be prudent for fully vaccinated people to get tested for Covid-19 if they develop symptoms similar to the disease.
“If you do get sick after vaccination, and it looks, smells and sounds like Covid-19, it could be Covid-19,” he said.
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