A young man from Nevada, the first successive contagion recorded in the United States, required oxygen when he became infected again. A Lancet study looked at what this case might mean for the treatments and vaccine currently being studied
This 25-year-old man, a resident of Washoe County, Nevada, United States, was the fifth person in the world who had the bad experience of contracting coronavirus twice. Due to this background, his case would not be news; however, he deserved a dedicated study in The Lancet Infectious Diseases because, misfortune also doubled, the second infection was much more serious than the first, with harder COVID-19 symptoms. The episode raised important questions about the duration of immunity that the human body can generate against SARS-CoV-2. When much of the hope of ending the pandemic focuses on the vaccine, observing the failure of immunity is daunting.
The first time the Nevada boy was tested on April 18, he had a sore throat and headache, cough, nausea and diarrhea. It had been like this for a few weeks; the test came back positive. He recovered, in isolation, on his own, and on April 27 he finally felt no symptoms at all. After that, in two checks carried out on May 9 and 26, he tested negative for SARS-CoV- 2, which declared him free of infection. As he had no other comorbidities, no special care was indicated.
However, two days later everything changed.
On May 28, the young man felt the same symptoms again, now complicated by fever and dizziness. His condition worsened, until on June 5, he had to consult his doctor. The coronavirus check tested him positive; his blood oxygen level was below what would have allowed him to return home, so he was referred to a hospital for admission. He was there until he regained his breathing.
To establish whether it was a recurrence of the first infection, the doctors compared the genome of the virus detected in the young man in April to the one detected in June: They found, surprisingly, that it was too different, said the study’s lead author, Mark Pandori from the University of Nevada. It was a new contagion, caused by a second transmission from another person.
An MIT Technology Review article highlighted the implication of such a finding: “Being infected once does not mean you’re protected from being infected again, even if such cases are still vanishingly rare, with just five identified out of nearly 40 million confirmed cases worldwide.”
In practice, this means that those who have survived COVID-19 cannot feel the relief of being immune, at least not completely: “people who have had covid-19 still need to stay vigilant, following the advice on social distancing, wearing face masks, and avoiding crowded, poorly ventilated spaces,” warned the Massachusetts Institute of Technology (MIT). For infectious disease experts, they added, it was not entirely unexpected bad news: “other coronaviruses, such as the common cold, are seasonal.”
“However, there are still many questions that researchers are racing to answer.” Among them: “How much protection does having COVID-19 confer? Does protection come primarily from antibodies or T leukocytes? How long does it last? And perhaps the most pressing question: “What does this mean for current medical treatments, and for vaccines?”.
The Lancet recalled that, as with other agents, the human body generates a detectable immune response against SARS-CoV-2, but “the susceptibility of previously infected people to re-infection is not well understood”, nor has it been elucidated “the extent to which this immune response indicates protective immunity to subsequent infection with SARS-CoV-2”. In studies on other coronaviruses, the scientific publication recalled, the immunity lasts between one and three years.
The case of the young man from Nevada, the first double contagion recorded in the United States, is another reminder of how little is still known about this novel disease. “The mechanisms that could explain why the second infection was more serious are only a matter of speculation,” the study continued. “In the first place, a very high dose of the virus could have caused the second instance of infection, and induced a more serious illness. Second, it is possible that the reinfection was caused by a more virulent version of the virus, or more virulent in the context of the patient ”.
It is also possible that, given the recent immune response to the first infection, the patient’s body has overreacted. “This has been documented in diseases such as dengue: antibodies made in response to one strain of the virus cause problems when infected with another strain,” interpreted the BBC. In other words, far from causing immunity, the first infection makes the second worse, due to the sensitivity of the body’s defence system.
“Our findings have implications for the role of vaccination in the response to COVID-19,” concluded Pandori and his colleagues. “If we really study a case of re-infection, the initial exposure to SARS-CoV-2 might not provide a 100% protective level of immunity for all individuals.” That is something that, in the case of the flu vaccine, for example, is well known: every year it must be adjusted according to the prevailing strains. According to scientists, that could be the case for the coronavirus as well.
Analyzing the study, Paul Hunter, from the University of East Anglia, told the BBC that the case was “very worrying”, given the short time that passed between one infection and another – which would indicate a very short immunity – and the severity of the second infection. However, since the pandemic has affected millions, that the instances of re-infection are so few is a sign that these are rare events. “It is too early to say with certainty what this finding means for an immunization program. But it reinforces the idea that we still do not know enough about the immune response to this infection”, he closed.