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The Lancet Infectious Diseases describes the first confirmed case of coronavirus reinfection in the United States, the country hardest hit by a pandemic in the world. This case shows that infection by the virus does not necessarily guarantee immunity in the future.
The patient, a 25-year-old man from Nevada, was infected with two strains of the COVID-19 virus, SARS-CoV-2, over a period of 48 days.
The course of the disease was more severe the second time he was infected; the patient had to be hospitalized with extra oxygen.
The article notes that four more cases of reinfection have been confirmed worldwide: one in Belgium, the Netherlands, Hong Kong and Ecuador.
According to experts, the prospect of reinfection could have a major impact on the way the world deals with a pandemic.
In particular, this could affect vaccine development, the current Holy Grail of pharmaceutical research.
“The possibility of reinfections could significantly alter our understanding of immunity to COVID-19, especially in the absence of an effective vaccine,” said Mark Pandori, lead author of the Nevada Public Health Laboratory.
“We need more research to understand how long people exposed to SARS-CoV-2 can have immunity and why some of these second infections … are more serious,” he added.
Weakened immunity?
Vaccines work by eliciting the body’s natural immune response to a certain pathogen by equipping the body with antibodies to fight future waves of infection.
However, it is not clear how long antibodies to COVID-19 remain in the body.
For some diseases, such as measles, immunity develops throughout life. Resistance to other pathogens can be short-lived.
The study authors note that the American patient in question may have been exposed to a large number of viruses for the second time, making his body’s response stronger.
Another possibility is that the patient has been infected a second time with a more aggressive strain of the virus.
Yet another hypothesis would be the operation of a mechanism called antibody-enhanced infection (ADE), where antibodies lead to subsequent stronger infections, as is the case with dengue fever.
The researchers note that any reinfection remains rare and that there are very few confirmed cases compared to the tens of millions of COVID-19 cases worldwide.
However, since many cases are asymptomatic and may go unnoticed, it may not be possible to determine whether a particular case of COVID-19 is a first or second infection.
Akiko Iwasaka, a Yale University professor of immunobiology who was not involved in the study, said the findings could affect public health measures.
“As more reinfections occur, the scientific community will better understand the correlations of protection, as well as the frequency with which natural infections with SARS-CoV-2 elicit this level of immunity,” he said.
“This information is very important in understanding which vaccines can cross that threshold and provide individual and herd immunity,” Iwasaka said.
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