A 25-year-old man from Nevada and a 42-year-old man in Virginia experienced second bouts of COVID-19 about 2 months after they tested positive the first time. Gene tests show both men had two slightly different strains of the virus, suggesting that they caught the infection twice, medscape.com reported Tuesday.
Researchers say these are the first documented cases of COVID-19 reinfection in the US. About two dozen other cases of COVID-19 reinfection have been reported around the globe, from Hong Kong, Belgium, the Netherlands, India, and Ecuador. A third US case, in a 60-year-old in Washington, has been reported but hasn't yet been peer reviewed.
Until now, immunologists haven't been too concerned about these reinfections because most second infections have been milder than the first, indicating that the immune system is doing its job and fighting off the virus when it is recognized a second time.
Unlike most of those cases, however, the men in Reno, Nevada, and Virginia, and a 46-year-old man in Ecuador, had more severe symptoms during their second infections, potentially complicating the development and deployment of effective vaccines.
The US cases are detailed in new studies published in The Lancet and the journal Clinical Infectious Diseases.
"Coronaviruses are known to reinfect people — the seasonal ones — and so it's not very surprising to see reinfections occurring with this particular coronavirus," said Akiko Iwasaki, PhD, an immunobiologist at Yale University who was not involved in either study. "And the fact that there is more severe disease the second time around. It could be a one-in-a-million event, we don't know. We're just becoming aware of the reinfection cases, and they are just a handful among millions of people infected."
The Nevada man originally got sick on March 25. His symptoms included a sore throat, cough, headache, nausea, and diarrhea. A test taken at a community event held on April 18 confirmed COVID-19. His symptoms gradually subsided and he reported feeling better on April 27. He tested negative for the virus twice after he recovered.
About a month later, the man went to an urgent care center with a fever, headache, dizziness, cough, nausea, and diarrhea. They sent him home. Five days later, he went to the doctor again, this time with difficulty breathing and low blood oxygen. They told him to go to the ER. He was admitted to the hospital on June 5. Lung X-rays showed telltale patches of cloudiness, known as ground-glass opacities, and a nasal swab test confirmed COVID-19. Gene testing of the two swabs, from April and June, showed key changes to the genetic instructions for the virus in the second test, suggesting that he'd gotten a slightly different strain the second time.
The Virginia man — a military health care provider — was infected the first time at work. He tested positive in late March after getting a cough, fever, and body aches. He recovered after 10 days and was well for nearly 2 more months. In late May, however, a member of his family got COVID-19, and he then got sick again with a fever, cough, difficulty breathing, and stomach upset. A chest X-ray confirmed pneumonia. His symptoms were worse the second time. Gene testing of the virus from each of his swabs indicated slight changes, suggesting he was infected twice.
Implications for vaccines
Akiko Iwasaki, an immunologist at Yale University and an investigator with the Howard Hughes Medical Institute, who wrote a commentary with the study said the study raises questions about how long immunity lasts after a natural infection. Protection with a vaccine is likely to be quite different, she said.
"Vaccines can be designed to induce much higher levels of antibody and much longer lasting immunity," she said. Just because the natural infection doesn't give you protection doesn't mean the vaccines cannot. It's a separate issue."
Offit, also a vaccine expert at the Perelman School of Medicine at the University of Pennsylvania, said he expects protection from vaccines will likely last at least a year or two.
The protection provided by infection or vaccination isn't 100% perfect until the day it disappears completely, he said. Instead, protection fades gradually, so someone exposed to a huge dose of the virus might get re-infected within months, while others could be protected for years, Offit said.
It's also possible the Nevada man has an undiagnosed problem with his immune system. "He probably should be seen by an immunologist," Offit said.
The length of time an infection will be protective remains one of the key open questions about the virus.
