Medical: My patient caught Covid-19 twice

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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The Guardian said:

People who have recovered from Covid-19 may lose their immunity to the disease within months, according to research suggesting the virus could reinfect people year after year, like common colds.

In the first longitudinal study of its kind, scientists analysed the immune response of more than 90 patients and healthcare workers at Guy’s and St Thomas’ NHS foundation trust and found levels of antibodies that can destroy the virus peaked about three weeks after the onset of symptoms then swiftly declined.

Blood tests revealed that while 60% of people marshalled a “potent” antibody response at the height of their battle with the virus, only 17% retained the same potency three months later. Antibody levels fell as much as 23-fold over the period. In some cases, they became undetectable.

“People are producing a reasonable antibody response to the virus, but it’s waning over a short period of time and depending on how high your peak is, that determines how long the antibodies are staying around,” said Dr Katie Doores, lead author on the study at King’s College London.

The study has implications for the development of a vaccine, and for the pursuit of “herd immunity” in the community over time.

The immune system has multiple ways to fight the coronavirus but if antibodies are the main line of defence, the findings suggested people could become reinfected in seasonal waves and that vaccines may not protect them for long.

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