In a new case study published in the British Medical Journal, doctors have warned that it might be possible for someone to have two completely separate bouts of COVID-19 infections, something that is not unheard of, but still uncommon. The findings come after doctors treated a man who had two separate infections four months apart with multiple negative tests in between.
The patient, a man in his 40s, had well-controlled type 2 diabetes, was obese, and had low thyroid function, all known risk factors for severe COVID-19 infections. He initially had severe COVID back in April 2020 and was hospitalized with breathing difficulties and required mechanical ventilation. He was treated with blood thinners and other COVID-19 medications and spent two months in hospital with various related medical conditions, such as kidney failure, a hospital-acquired infection (MRSA), gastrointestinal bleeding, and ventilator-associated pneumonia. He eventually recovered and was discharged from the hospital to a rehabilitation care center.
He then acquired a second infection in August 2020, four months after testing positive the first time, and having had four negative COVID-19 tests in the months proceeding. For the second infection, his symptoms were much milder and he stayed in hospital for just one day, initially.
He was discharged but returned two weeks later, complaining of shortness of breath. He again tested positive for the virus and was treated in hospital for a week.
The authors of the case report suggest that the positive COVID-19 tests months apart after testing negative four times in between may mean that the man had been reinfected with the virus. Furthermore, because he had a much milder second infection, they suggest it may have been due to the residual immunity he had leftover after the first more severe infection.
"As the COVID-19 pandemic has evolved, emerging reports have shown that SARS-CoV-2 reinfection is possible, such that positive SARS-CoV-2 RNA testing over a long period of time does not necessarily indicate persistent viral shedding from prior COVID-19 infection." the authors wrote in the general report.
Not much is known about how COVID-19 reinfections work and whether there is full or partial immunity from antibodies after the first round of infection. A rare case in the US reported a man that was reinfected but suffered a more severe COVID-19 experience the second time around.
"The role of the presence or absence of antibodies after initial infection in survivors of a first episode of COVID-19 and its role in mitigating the risk of SARS-CoV-2 reinfection is not clearly defined. It is plausible, however, that waning immunity or absence of antibodies after the first episode of SARS CoV-2 infection may make one more susceptible to reinfection." the authors said in a statement.
Only around 100 cases of reinfection have been reported around the world so it appears currently that reinfection is rare. However, more work will need to be carried out to understand long-term immunity and the chances of being reinfected, especially now that various new variants of SARS-CoV-2 have emerged around the world.
