Experts say reinfections are not surprising, but they are likely to be rare and not necessarily serious in any case
Months after the start of the COVID-19 pandemic, cases of reinfection with the new coronavirus were documented this week.
The first was reported in Hong Kong Monday. A day later, scientists from Holland and Belgium they also confirmed their first cases of reinfection.
Although there were suspected cases of reinfection, these are the first scientifically proven, as confirming a reinfection requires genetic testing on both the first and second infection to see if there are differences in the virus.
Experts say reinfection is not surprising, but it is likely rare and larger studies are needed to understand why this may happen.
However, the confirmation that there may be reinfection of the new coronavirus provides new data on the duration of immunity, and understanding this has implications in the development of a vaccine.
What is known about reinfection cases
Hong Kong scientists reported on Monday the case of a 33-year-old man who suffered from the new coronavirus in March and was reinfected four and a half months later, on a trip to Spain in August.
They explained that genome sequencing shows that the two strains of the virus are “clearly different”, making it the first proven case of reinfection in the world.
In the University of Hong Kong report, published in the medical journal Clinical Infectious Diseases, it is stated that the man spent 14 days in hospital before recovering from the virus, but then, despite have no symptoms, tested positive again for the second time after a saliva test during inspection at the airport.
Later, on Tuesday, virologist Marion Koopmans, director of the Virology department at Erasmus MC, confirmed the first case of reinfection in the Netherlands.
It is a elderly person with a “impaired” immune system. Koopmans did not detail the patient’s symptoms out of the need to “see if it happens more often,” he told Dutch television NOS.
That same day, virologist Marc Van Ranst confirmed that a Belgian citizen who had already overcome the coronavirus had also been reinfected three months after the first infection. The woman had mild symptoms and did not require hospitalization, according to Ranst.
The duration of immunity
Experts believe that reinfections are not necessarily serious, as those infected develop an immune response as their bodies fight the virus, which helps protect against its return.
But it is not yet clear how strong this protection or immunity is, or how long it lasts.
Immunity is the set of mechanisms that protect us from infections. There are two kinds: the innate and the adaptive.
The first kicks in as soon as a foreign invader is detected in the body and includes the release of chemicals that cause inflammation and white blood cells to destroy infected cells.
Meanwhile, adaptive immunity establishes a specific response against the specific infectious agent. It includes cells that produce targeted antibodies that can attach to the virus to stop it, and T cells, which can attack only cells infected with the virus, which is called the cellular response.
This adaptive response takes several days to arrive and one of its features is that leave memory. That is, remember the pathogens that your body has come into contact with in the past, and therefore you will know how to combat them in the future.
What virologists around the world are now trying to determine is howtor can that immunity last for COVID-19.
“Our bodies do not become impermeable to viruses when we recover from an infection, but, in many cases, they become inhospitable guestsZania Stamataki, a virologist at the University of Birmingham, wrote in an article in The Conversation.
“However, if the antibodies and memory cells (B and T cells) are left from a recent infection, the new virus expansion is short-lived and the infection is suppressed before the host suffers too much, or even give account ”.
For Stamataki, this appears to be the case for the Hong Kong patient, who did not show any symptoms of the second infection, which was discovered after routine tests at the airport.
Why it can be good news
The specialist from the University of Birmingham explains that there are three possible outcomes when there is a reinfection: worse symptoms leading to a more serious illness, the same symptoms as the first infection, and an improvement in symptoms leading to a milder or asymptomatic illness.
“The first result is known as disease improvement and it is seen in patients infected with similar strains of viruses such as dengue, “wrote Stamataki, adding that” there is no evidence of this for the new coronavirus, despite the fact that there are more than 23 million confirmed cases of covid-19 worldwide. the world”.
“The second result, where the patient suffers same disease twice, indicates that there is not enough immunological memory left to protect against reinfection “, indicated the virologist in her article in The Conversation.
Stamataki explained that this can happen when the innate response, which does not require T cells, is sufficient to control the infection.
On the other hand, the expert writes, when there is a reinfection but it presents milder symptoms or does not present symptoms, that indicates that antibodies and B and T cell response persisted long enough as to protect from infection.
Therefore, according to the expert, “the absence of symptoms experienced by the Hong Kong patient is very good news“.
Stamataki indicates that “this has implications for the potency and duration of herd immunity, the idea that when we reach a large number of recovered patients immune to reinfection, this will protect the most vulnerable.”
And also for the development of the vaccine against COVID-19.
“Vaccination can elicit stronger and longer-lasting immune responses compared to natural infection, and these can be maintained with booster vaccinations when necessary,” adds the expert.
“Therefore scientists weren’t surprised to hear evidence of reinfection“.
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