First case of coronavirus reinfection confirmed, researchers say

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By Yasemin Saplakoglu
published

A man in Hong Kong was reinfected with the novel coronavirus, but didn't develop any symptoms the second time.

People wearing masks in a metro station in Hong Kong on March 3.
(Image credit: Shutterstock)

A man in Hong Kong is the first with a confirmed reinfection with the novel coronavirus, a new study suggests.

This may be the first major clue to a still-unanswered question about the COVID-19 pandemic: How long does immunity to SARS-CoV-2 last? There have been some previous reports of potential reinfection cases around the globe, but none have been confirmed with definitive testing, according to The New York Times. People who recover from COVID-19 can shed virus fragments for weeks, which can turn up as a positive COVID-19 test results, even when they aren't actually shedding live virus, according to The Times.

But today (Aug. 24), a group of researchers reported on a case of a patient who was infected with two genetically different strains of the coronavirus, months apart, according to a press release from the University of Hong Kong's Department of Medicine. The scientists found that the coronavirus that infected the patient, a 33-year-old-man in Hong Kong, the second time around had 24 different nucleotides, or building blocks, in its gene sequence than the virus that infected him the first time. 

Related: Coronavirus live updates

That likely means that the person didn't just continue to shed the same virus months after being infected, according to the study that was just accepted, but not yet published, in the journal Clinical Infectious Diseases.

But this case shouldn't spark widespread fear.

"This is no cause for alarm - this is a textbook example of how immunity should work," Akiko Iwasaki, a professor of immunobiology and molecular, cellular and developmental biology at the Yale School of Medicine, wrote on Twitter.

The patient, who was previously healthy, was first diagnosed with COVID-19 on March 26. During his first infection he had mild symptoms including a cough, sore throat, headache and fever for several days. Though his symptoms subsided, he was hospitalized on March 29  and was discharged on April 14 after testing negative for the virus twice.

Four and half months later, the patient was returning to Hong Kong from Spain via the United Kingdom and tested positive for the virus in a screening at the Hong Kong airport on Aug. 15, according to the report. He was again hospitalized but didn't have any symptoms. "While immunity was not enough to block reinfection, it protected the person from disease," Iwasaki wrote.

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Antibody tests showed that the patient did not have any detectable antibody to the coronavirus when he was reinfected but developed detectable antibodies after reinfection. 

"This is encouraging," Iwasaki wrote. "While this is a good example of how primary infection can prevent disease from subsequent infection, more studies are needed to understand the range of outcomes from reinfection."

This case of re-infection has "several important implications," the authors wrote in the study. "It is unlikely that herd immunity can eliminate SARS-CoV-2, although it is possible that subsequent infections may be milder than the first infection as for this patient." 

COVID-19 will likely continue to circulate in the human population, similar to the coronaviruses that cause common colds, they wrote.

Other implications are that vaccines may not be able to provide lifelong protection against COVID-19 and that vaccines studies should include those who have recovered from COVID-19, the authors wrote. 

“What I think is really important is that we put this into context,” Maria Van Kerkhove, the World Health Organization's technical lead for coronavirus response and head of the emerging diseases and zoonoses unit, said during a news briefing in Geneva on Monday (Aug. 24), according to CNN. There's been more than 24 million cases of COVID-19 reported worldwide, and so "we need to look at something like this on a population level."

Van Kerkhove said she was still reviewing the case, according to STAT News.  "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." 

Originally published on Live Science.

Yasemin Saplakoglu
Yasemin Saplakoglu
Staff Writer

Yasemin is a staff writer at Live Science, covering health, neuroscience and biology. Her work has appeared in Scientific American, Science and the San Jose Mercury News. She has a bachelor's degree in biomedical engineering from the University of Connecticut and a graduate certificate in science communication from the University of California, Santa Cruz.

2 Comments Comment from the forums
  • Dipankar18
    admin said:
    A man in Hong Kong was reinfected with the novel coronavirus twice, but didn't develop any symptoms the second time.

    First case of coronavirus reinfection confirmed, researchers say : Read more
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  • RobertPolaris
    admin said:
    A man in Hong Kong was reinfected with the novel coronavirus twice, but didn't develop any symptoms the second time.

    First case of coronavirus reinfection confirmed, researchers say : Read more
    And yet After six months of the Corona pandemic, a body of scientific work is emerging that shows our immune system is capable of remembering Corona and producing a lasting immunity.

    This immunology work also supports the theory of cross-protection, whereby the body can mount a timely and appropriate defense on the simple inference that Sars-CoV-2 is a lot like other coronaviruses.


    Over the course of the pandemic, medical fears have been shaped as much by what the future holds in terms of second waves and mutations during the cold of winter, as by what has been happening in the world at any particular moment.

    However, studies both peer-reviewed and not, are seeing positive changes in the human innate immune response to Corona that suggest the diseases’ days of unfettered infection are numbered.

    For example, in one peer reviewed study from Nature, immunologists in Singapore studied the cellular memory of T-cells, an important immune cell that weaponizes other immune responses in addition to tracking and eliminating pathogens on their own.

    The researchers found that:

    People with or recovering from Corona displayed immediate memory T-cell activation to the virus’ proteins.
    People with an infection history—going back as far as 17 years—of SARS-CoV-1 which emerged in China around 2002-2003, had long-lasting memory T-cell responses that ”displayed robust cross-reactivity to the N protein of SARS-CoV-2.”
    And, perhaps most interesting, SARS-CoV-2-specific memory T-cell activation was found “in individuals with no history of SARS, Corona or contact with individuals who had SARS and/or Corona.”The last point is certainly enough to give us hope. And yet more positive research emerges.

    Another study, this one not yet peer-reviewed, found that the response of antibodies—one of the primary classes of immune cells used to defend against pathogens—stayed active in saliva up to 115 days after the onset of symptoms in Corona patients.

    While antibody and T-cell responses in the blood have been extensively studied, this work, published in the preprint publication, has been one of the first to look at responses in mucus cells. The scientists note this is an important area of research since the virus infects in the upper respiratory tract.

    “The immune response is doing exactly what we would expect it to,” Gommerman, an immunologist at the University of Toronto who worked on the study, told CNN. “At least at about four months, which is, as far as, most of us can measure at this point in the pandemic.”

    Work on yet another kind of immune cell, the ‘helper’ T-cell as opposed to the ‘killer’ T-cell, was completed earlier in the year when several studies published in Nature and Science found that the helpers could also, more than half the time, identify Corona and sound the alarm, and that these helpers were present in patients that had never been exposed to Corona.

    The evidence of re-infection is, at this point, non-existent, which suggests humanity’s collective immune system is working well to combat it.

    “So that is all good news,” Gommerman said. ”That means that people who are infected with this novel Coronavirus should have the capacity to mount what’s called a memory immune response to protect themselves against infection.”
    Reply