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Re-infection with Covid-19 calls into question viral immunity: a study


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Patients with COVID-19 may experience more severe symptoms a second time when they are infected, according to a study published Tuesday confirming that it is possible to become infected with a potentially deadly disease more than once.

A study published in Lancet infectious diseases The journal describes the first confirmed case of reinfection of COVID-1

9 in the United States, the country hardest hit by the pandemic, and says 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, over a 48-day period.

The second infection is more severe than the first, as a result of which the patient is hospitalized with oxygen support.

The newspaper notes four more cases of reinfection confirmed worldwide, with one patient each in Belgium, the Netherlands, Hong Kong and Ecuador.

Experts say the prospect of reinfection could have a profound effect on the way the world is battling the pandemic.

In particular, this could affect the vaccine hunt – currently the Holy Grail of pharmaceutical research.

“The possibility of re-infections can have significant implications for our understanding of immunity to COVID-19, 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 severe.”

Decreased immunity?

Vaccines work by triggering the body’s natural immune response to a specific pathogen, arming it with antibodies to fight future waves of infection.

But it is not at all clear how long the antibodies against COVID-19 last.

For some diseases, such as measles, the infection provides lifelong immunity. For other pathogens, immunity may be transient at best.

The authors say the US patient may have been exposed to a very high dose of the virus a second time, causing a more severe reaction.

Alternatively, it may be a more virulent strain of the virus.

Another hypothesis is a mechanism known as antibody-dependent amplification – i. when the antibodies actually worsen subsequent infections, such as dengue fever.

The researchers said that reinfection of any kind remains rare, with only tens of confirmed cases of tens of millions of COVID-19 infections worldwide remaining rare.

However, because many cases are asymptomatic and therefore unlikely to be tested positive initially, it may be impossible to know whether a case of COVID-19 is the first or second infection.

In a related commentary for The Lancet, Akiko Iwasaka, a 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 increase, the scientific community will have the opportunity to better understand the correlates of protection and how often natural SARS-CoV-2 infections induce this level of immunity,” she said.

“This information is key to understanding which vaccines can cross this threshold to provide individual and herd immunity,” added Iwasaka, who was not involved in the study.

The clinical study aims to better understand the immunity of COVID-19

© 2020 AFP

Quote: Reinfection of Covid-19 calls into question viral immunity: study (2020, 13 October), retrieved on 13 October 2020 from https://medicalxpress.com/news/2020-10-covid-reinfection-virus-immunity.html

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