““Wait. I can catch Covid twice?” my 50-year-old patient asked in disbelief. It was the beginning of July, and he had just tested positive for SARS-CoV-2, the virus that causes Covid-19, for a second time — three months after a previous infection.
While there’s still much we don’t understand about immunity to this new illness, a small but growing number of cases like his suggest the answer is yes.
Covid-19 may also be much worse the second time around. During his first infection, my patient experienced a mild cough and sore throat. His second infection, in contrast, was marked by a high fever, shortness of breath, and hypoxia, resulting in multiple trips to the hospital.
Recent reports and conversations with physician colleagues suggest my patient is not alone. Two patients in New Jersey, for instance, appear to have contracted Covid-19 a second time almost two months after fully recovering from their first infection. Daniel Griffin, a physician and researcher at Columbia University in New York, recently described a case of presumed reinfection on the This Week in Virology podcast.
It is possible, but unlikely, that my patient had a single infection that lasted three months. Some Covid-19 patients (now dubbed “long haulers”) do appear to suffer persistent infections and symptoms.
My patient, however, cleared his infection — he had two negative PCR tests after his first infection — and felt healthy for nearly six weeks.”
“repeat infections in a short period are a feature of many viruses, including other coronaviruses. So if some Covid-19 patients are getting reinfected after a second exposure, it would not be particularly unusual.”
“Herd immunity depends on the theory that our immune systems, once exposed to a pathogen, will collectively protect us as a community from reinfection and further spread.”
“Experts generally consider natural herd immunity a worst-case-scenario backup plan. It requires mass infection (and, in the case of Covid-19, massive loss of life because of the disease’s fatality rate) before protection takes hold.”