It may be possible to have two separate episodes of serious COVID-19 infection because of waning immunity, doctors have warned.
Writing in BMJ Case Reports, researchers at the Department of Internal Medicine, Section of Infectious Diseases, at Yale University School of Medicine, New Haven, USA, say a man in his 40s was treated twice, with infections separated by four months of no symptoms and serial negative tests for the virus.
They suggest severe infection first time may be followed by subsequent milder symptoms.
The patient, who had well-controlled type 2 diabetes, an underactive thyroid gland, and was obese, was first admitted to hospital in April 2020 with severe COVID-19, having breathing difficulties and a high-pitched wheeze caused by stridor.
He developed respiratory failure and required mechanical ventilation, blood thinners and other drugs to treat the virus.
During his two-month hospital stay, he developed serious complications, including MRSA, gastrointestinal bleeding, ventilator-associated pneumonia and kidney failure. When he stabilised, he was subsequently discharged to an acute care facility for rehabilitation.
In August 2020, he tested positive for SARS-CoV-2, following four interval negative tests in the preceding three months, and stayed in hospital for one day.
However, he was readmitted two weeks later with shortness of breath and told doctors he had had intermittent episodes of choking, shortness of breath and stridor. This third hospital stay lasted a week.
He tested positive for SARS-CoV-2 and claimed he had had little exposure to other people, except for relatives and immediate family, none of whom had symptoms or had been recently ill.
The authors write that the subsequent positive test might be attributable to re-infection with the virus and the milder symptoms second time around could be because of residual immunity from the first severe infection.
Although the Centers for Disease Control and Prevention (CDC) suggest a positive SARS-CoV-2 swab test within 90 days of an initial infection may represent sustained viral shedding rather than reinfection, the authors say: “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.”
They add: “If patients with severe disease develop more robust antibody levels, their duration of protection against re-infection and resulting severity of disease, if it does occur, may be muted. Future observations would certainly shed more light on this if this hypothesis holds true.
“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 re-infection 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 re-infection.”
Tuan J, Spichler-Moffarah A, Ogbuagu O. A new positive SARS-CoV-2 test months after severe COVID-19 illness: reinfection or intermittent viral shedding? BMJ Case Reports 5 February 2021; doi 10.1136/bcr-2020- 240531
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