COVID and Reinfection
The question is, can a patient who has had COVID be re-infected by the SARS-CoV-2 virus?
The press recently have documented that there appears to have been a case of reinfection in Hong Kong during August.
Is this the case? What are the implications for immunity and vaccination? Professor Justin Stebbing has helped us to answer this question.
It appears that the 33-year-old gentleman from Hong Kong was infected in March, having symptoms of fever, cough, sore throat and headache. He tested positive for coronavirus and was then admitted to hospital three days later. At the point of admission, his symptoms were alleviated and he was discharged in April when he tested negative for the virus on two occasions.
He was then tested four months later in August on return to Hong Kong from Spain at Hong Kong airport. Interestingly enough, he did not have any symptoms in August. This might indicate that his immune system was working, as he remained asymptomatic but did not have enough immunity to prevent reinfection.
The viruses from the two episodes differed in their nucleotides. This would indicate that he was infected at two different times by two differing mutations of SARS-CoV-2. It was apparent that one was closely related to variants circulating in the United States and England in March and April, and the other was related to viruses from Switzerland and England in July and August.
Ten days after the patient developed symptoms for the first time, he tested negative for antibodies against the virus; however, it may have been too early to detect the antibodies. The second time, in August, he also did not have antibodies in his first three days in hospital. He tested positive on the fifth day, indicating that his immune response was beginning to fight the virus.
Professor Stebbing, who has presented the case in writing to us in detail, suggests that although it would appear reinfection is possible, he points out that the immune system is doing its job. As the patient originally tested negative for antibodies during his first infection and, unfortunately, the antibody levels were not monitored over time, it is not possible to know the magnitude of his immune response.
However, a preprint published by Ania Wajnberg reports that the vast majority of infected individuals with mild to moderate COVID-19 experience a robust IgG antibody response against the viral spike protein. This was based on a data set of 19,860 individuals who were screened at Mount Sinai Hospital in New York City. In this preprint, they also showed that titres were stable for at least a period of approximately three months, and that the anti-spike binding titres significantly correlated with the neutralisation of SARS-CoV-2. Their data suggested that more than 90% of seroconvertors make detectable neutralising antibody responses and these titres are stable for at least the near-term future.
Unfortunately, the T-cell response has not been measured and, although it is clear that the gentleman from Hong Kong did have a second reinfection by a mutant SARS-CoV-2 virus, his response was limited and he was asymptomatic. The T-cell response, which may have helped to also reduce his symptoms, has not been measured and the other consideration here is was he infectious, as the amount of virus particle has not been indicated.
We should also consider the fact that millions of people have been infected with SARS-CoV-2, but as yet, this is the only one individual case in which reinfection has been proven.
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