https://www.vox.com/2020/7/12/21321653/getting-covid-19-twice-reinfection-antibody-herd-immunity
Vox said:“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 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.
I believe it is far more likely that my patient fully recovered from his first infection, then caught Covid-19 a second time after being exposed to a young adult family member with the virus. He was unable to get an antibody test after his first infection, so we do not know whether his immune system mounted an effective antibody response or not.
Regardless, the limited research so far on recovered Covid-19 patients shows that not all patients develop antibodies after infection. Some patients, and particularly those who never develop symptoms, mount an antibody response immediately after infection only to have it wane quickly afterward — an issue of increasing scientific concern.
What’s more, repeat infections in a short time 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.
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