World's First Confirmed Case of COVID-19 Re-Infection Raises Questions Over Coronavirus Immunity

Researchers have reported the world’s first confirmed case of COVID-19 re-infection, raising questions about the durability of immune protection from the SARS-CoV-2 virus.

Researchers have confirmed that a 33-year-old man was first infected by SARS-CoV-2 in late March and then again contracted the virus after four and a half months while traveling in Europe, according to a report by STAT. There have been reports earlier of cases of COVID-19 re-infection, although they were based on anecdotal evidence and had been attributed mainly to flaws in testing. However, in this latest case of COVID-19 re-infection, researchers from the University of Hong Kong (Hong Kong) sequenced the virus from the patient’s two infections and found that they did not match, indicating that the second infection was not linked to the first. The researchers found a difference of 24 nucleotides, the “letters” that make up the virus’ RNA, between the two infections.


The finding of the world’s first confirmed case of COVID-19 re-infection comes amidst concerns over how long one can remain protected from the SARS-CoV-2 virus after being infected and recovering. Various studies have found that the majority of recovered COVID-19 patients generate a robust immune response involving both antibodies (molecules that can block the virus from infecting cells again) and T cells (which can help clear the virus), according to the STAT report. This indicates protection from repeat COVID-19 infection could last for some time. However, experts believe that immunity to SARS-CoV-2 cannot last forever as people generally once again become susceptible to the coronaviruses that cause common cold after a year or even less, and remain protected against SARS-1 and MERS for just a few years.

Nevertheless, experts believe that the Hong Kong case is rare and unprecedented among the tens of millions of cases globally and immune protection to COVID-19 may generally last more than a few months. More definitive conclusions could be reached only after the conclusion of studies currently tracking patients who have recovered from COVID-19. Additionally, experts have pointed out that that the Hong Kong man’s second case was milder than his first, indicating that his immune system was providing some protection against the SARS-CoV-2 virus, even if it failed to prevent re-infection entirely, according to STAT.

“There’s been more than 24 million cases reported to date,” Maria Van Kerkhove, a coronavirus expert at the World Health Organization, said at a briefing, when asked about the Hong Kong report. “And we need to look at something like this at a population level. What we are learning about infection is that people do develop an immune response, and what is not completely clear yet is how strong that immune response is and for how long that immune response lasts.”

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