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Can we catch COVID two times?

Text updated on 2020-09-24

Yes, it is possible to catch COVID-19 several times.

SARS-CoV-2 coronavirus  reinfection has recently been demonstrated in a few patients. The possibility of being re-infected with the COVID 19 virus had been suspected for several months. Indeed, cases of cured and negatively tested patients regaining symptoms and/or carrying viral RNA have been observed in different countries. However, the detection of the virus in "cured" patients can be interpreted in two different ways: either a return of the first infection, which in reality would not have been completely eliminated but would have fallen below the detection threshold of the tests, or a real new infection. A comparison of the sequence of viral RNA in the first and "second" infection allows us to distinguish between these two possibilities: an identical or very similar sequence is compatible with a resurgence of the first infection, whereas significant differences between the viral RNA detected during the two infectious episodes are indicative of two independent infections. This has been observed in a few patients.

Two cases have been reported: in some patients, symptoms were more severe the second time and in others, symptoms were less severe than the first COVID-19 infection. For example, a 33-year-old resident of Hong Kong had no symptoms during reinfection while a 25-year-old resident of Reno, Nevada (USA) had a severe form of COVID-19 during re-infection, but not during his first infection.

In the case of the viruses that cause colds (HCoV: NL63, 229E, OC43 and HKU1), which also belong to the coronavirus family and for which more information is available, a person is re-infected on average every 3 years and a second infection may occur only 6 months after the previous one. For the SARS-CoV-2 COVID-19 virus, our knowledge is still too limited to estimate the probability of reinfection.

The few observed cases of re-infection of COVID-19 are asking important questions for which we do not yet have a clear answer: How often do these reinfections occur? What are the consequences for patients and the dynamics of the pandemic? What are the implications for vaccine development?

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Study reporting the case of a patient who tested positive for the SARS-CoV-2 coronavirus on his return from Spain, at the Hong Kong airport, four and a half months after a first infection. The differences between the viral RNA sequences collected during the two infectious episodes confirm that these are two successive independent infections.

To, K. K. W., Hung, I. F. N., Ip, J. D., Chu, A. W. H., Chan, W. M., Tam, A. R., ... & Lee, L. L. Y. (2020). COVID-19 re-infection by a phylogenetically distinct SARS-coronavirus-2 strain confirmed by whole genome sequencing. Clinical Infectious Diseases.

In this preprint, the authors report the case of a 25-year-old patient from Reno, Nevada, who developed a severe form of COVID-19 (with hospitalization and need for continuous oxygen supply) one month after the end of symptoms associated with a first infection that did not require hospitalization. Differences in viral RNA sequences between the two infectious episodes confirm that this is a reinfection and not a resurgence of the first infection.

Tillett, R., Sevinsky, J., Hartley, P., Kerwin, H., Crawford, N., Gorzalski, A., ... & Farrell, M. (2020). Genomic Evidence for a Case of Reinfection with SARS-CoV-2. Available at SSRN 3680955.

This commentary in the journal Nature explores the questions posed by the two studies above regarding the spread of COVID-19 and the development of a vaccine.

Ledford H. (2020). Coronavirus reinfections: three questions scientists are asking. Nature, 10.1038/d41586-020-02506-y. Advance online publication.

SARS-CoV-2 coronavirus reinfection in macaques.

Chandrashekar, A., Liu, J., Martinot, A. J., McMahan, K., Mercado, N. B., Peter, L., ... & Busman-Sahay, K. (2020). SARS-CoV-2 infection protects against rechallenge in rhesus macaques. Science.

Analysis of serological and clinical data accumulated in the Netherlands in ten men (aged 27-40 years at the start of the study) for 35 years, from 1985 to 2020, who volunteered to have blood samples taken approximately every 3-6 months. A total of 132 common cold coronavirus (HCoV: NL63, 229E, OC43 and HKU1) infections were detected, i.e. between 3 and 22 infections per individual. A similar median reinfection time of approximately 30 months was measured for each of the 4 cold coronaviruses. In some cases, re-infection with the same coronavirus occurred 6 months after the first one. For each coronavirus, there are half as many infections from May to September as from December to March.

Edridge, A. W., Kaczorowska, J., Hoste, A. C., Bakker, M., Klein, M., Loens, K., ... & Ieven, M. (2020). Seasonal coronavirus protective immunity is short-lasting. Nature Medicine, 1-3.

Cases of reinfection 93 days after the first infection. Differences in the viral RNA sequences of the two infectious episodes suggest reinfection.

Van Elslande, J., Vermeersch, P., Vandervoort, K., Wawina-Bokalanga, T., Vanmechelen, B., Wollants, E., ... & Maes, P. (2020). Symptomatic SARS-CoV-2 reinfection by a phylogenetically distinct strain. Clinical infectious diseases: an official publication of the Infectious Diseases Society of America, ciaa1330.

Cases of reinfections in two clinicians in India. Differences in the viral RNA sequences of the two infectious episodes suggest that this is indeed a reinfection.

Gupta, V., Bhoyar, R. C., Jain, A., Srivastava, S., Upadhayayay, R., Imran, M., ... & Gupta, R. (2020). Asymptomatic reinfection in two healthcare workers from India with genetically distinctSARS-CoV-2. Preprint

Cases of reinfection 51 days after the first infection. Differences in the viral RNA sequences of the two infectious episodes suggest reinfection.

Larson, D., Brodniak, S. L., Voegtly, L. J., Cer, R. Z., Glang, L. A., Malagon, F. J., ... & Burgess, T. (2020). A Case of Early Re-infection with SARS-CoV-2. Clinical infectious diseases: an official publication of the Infectious Diseases Society of America, ciaa1436

Regularly updated table of re-infection COVID cases reported worldwide. As of September 24, 2020, there were 15 cases of re-infection.

BNO News article updated regularly.

Further reading

How does she get COVID-19 ?

Is the SARS-CoV-2 coronavirus transmitted by aerosols?

Do I have to wear a mask inside / outside?

Do I have to wear a mask if I already had COVID-19?