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PARIS (AFP) – Covid-19 patients may experience more severe symptoms the second time they are infected, according to research published on Tuesday (October 13) that confirms that it is possible to contract the life-threatening disease more than once.
A study published in the journal The Lancet Infectious Diseases traces the first confirmed case of Covid-19 reinfection in the United States, the country most affected by the pandemic, and indicates that exposure to the virus may not guarantee future immunity.
The patient, a 25-year-old man from Nevada, was infected with two different variants of Sars-CoV-2, the virus that causes Covid-19, within a 48-day period.
The second infection was more serious than the first, so the patient was hospitalized on oxygen support.
The document pointed to four other confirmed reinfection cases globally, with one patient in each from Belgium, the Netherlands, Hong Kong and Ecuador.
Experts said the prospect of reinfection could have a profound impact on how the world fights the pandemic.
In particular, it could influence the search for a vaccine, the current Holy Grail of pharmaceutical research.
“The possibility of reinfections could have significant implications for our understanding of Covid-19 immunity, especially in the absence of an effective vaccine,” said Mark Pandori of the Nevada State Public Health Laboratory and lead author of the study.
“We need more research to understand how long immunity can last for people exposed to Sars-CoV-2 and why some of these second infections, although rare, present as more serious.”
DO YOU WANT IMMUNITY?
Vaccines work by triggering the body’s natural immune response to a certain pathogen, arming it with antibodies to fight future waves of infection.
But it is not entirely clear how long Covid-19 antibodies last.
For some diseases, such as measles, the infection confers lifelong immunity. For other pathogens, immunity can be fleeting at best.
The authors said the American patient could have been exposed to a very high dose of the virus the second time, triggering a more acute reaction.
Alternatively, it may have been a more virulent strain of the virus.
Another hypothesis is a mechanism known as antibody-dependent enhancement, that is, when antibodies actually worsen subsequent infections, such as with dengue.
The researchers noted that reinfection of any kind remains rare, with only a handful of confirmed cases out of tens of millions of Covid-19 infections worldwide.
However, since many cases are asymptomatic and therefore unlikely to have initially tested positive, it may be impossible to tell whether a given Covid-19 case is the first or the second infection.
In a comment linked to the Lancet article, Akiko Iwasaka, Professor of Immunobiology and Molecular, Cellular and Developmental Biology at Yale University, said the findings could affect public health measures.
“As more cases of reinfection emerge, the scientific community will have the opportunity to better understand the correlates of protection and how often natural infections with Sars-CoV-2 induce that level of immunity,” he said.
“This information is key to understanding which vaccines are capable of crossing that threshold to confer individual and herd immunity,” added Iwasaka, who was not involved in the study.
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