According to a study published today in the scientific journal Lancet, exposure to the new coronavirus may not translate into guaranteed total immunity to covid-19 disease and researchers point to the need for further analysis of cases of reinfection.
What is known so far about reinfection with SARS-CoV-2:
How many cases of reinfection are there?
The study released today in the Lancet magazine confirms the first case of reinfection by the new coronavirus in the United States, the fifth worldwide. The first was registered in Hong Kong on August 24 and the rest in Belgium, the Netherlands and Ecuador.
However, researchers in South Korea and Israel have already described other cases of reinfection, resulting in less than 20 possible reinfections, compared to the more than 37.5 million confirmed cases of infection worldwide.
“It does not mean that there are no more”, warns Mark Pandori, one of the authors of the research published today on the American patient.
Many infected people do not show symptoms of covid-19, the disease caused by the new coronavirus, which makes diagnosis difficult, and one of the five cases of reinfection, the Hong Kong patient, was discovered by chance through a screening test in the airport.
Confirmation that this is a reinfection also implies a genetic analysis of the samples taken from each of the infections, to check whether or not two different strains of the virus are involved, a procedure that is difficult to implement on a large scale.
What are the consequences of reinfection for patients?
The consequences of a reinfection vary from case to case, and if for patients in the United States and Ecuador the second infection was more serious than the first, in the remaining cases this worsening was not seen.
For researchers in the Lancet study, the fact that the Hong Kong patient did not develop symptoms at the second infection is good news and a sign that his immune system has learned to defend itself after the first infection.
On the other hand, the patient from the United States was hospitalized and received oxygen during the second infection, despite having mild symptoms the first time.
“It is worrying,” said Yale University immunity expert Akiko Iwasaki, quoted by AFP in a comment on the investigation.
According to the authors, a hypothesis to explain the worsening of symptoms in the second infection is the possible exposure to a very large inoculum of the virus the second time, “which would have caused a more acute reaction”.
The explanation may also include exposure to a more virulent strain of the virus or the fact that the second infection was facilitated by the presence of antibodies due to the first (a possibility in other diseases, such as dengue).
On the other hand, Dutch researchers also recently described the case of an 89-year-old woman who died after a reinfection, even though the victim suffered from a rare cancer that weakened her immune system.
What are the implications for the pandemic?
The cases of reinfection, although rare, cast doubt on the debate on immunity against SARS-CoV-2 and on the possible duration of that immunity.
The re-infections identified in the United States and Hong Kong occurred in a relatively short period: four and a half months between the first and the second infection for the Hong Kong patient and up to 48 days for the United States.
“Examples of other coronaviruses, responsible for common flu and severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), show that there is no lifelong immunity,” said a World Health Organization expert, Maria recently. van Kerkhove.
Mark Pandori warns that people who have already been exposed to the new coronavirus should continue to take precautions, including physical distance, the use of a mask and hand hygiene, since the possibility of reinfection is not excluded.
Researchers have also been trying to understand why some people may be re-infected and a researcher from the French National Institute of Health and Medical Research, Frédéric Altare, heard by AFP, explained that these cases have been extensively studied in an attempt to identify a differentiating factor that can justify reinfection.
Whatever the reason, says researcher Akiko Iwasaki, “reinfections show that we cannot rely on the immunity acquired through natural infection to achieve group immunity”, stressing that the strategy is ineffective and can be fatal for many people.
What are the implications for creating a future vaccine?
“The fact that reinfections are possible may mean that a vaccine would not be completely protective. But as the number of cases is minuscule, this should not deter us from developing them ”, says a professor at the London School of Hygiene and Tropical Medicine, Brendan Wren, cited by the British organization Science Media Center (SMC).
The Global Vaccination Alliance (Gavi) – whose former Portuguese prime minister and ex-president of the European Commission, José Manuel Barroso, has been appointed – recognizes that the ability to develop an effective vaccine against covid-19 is unknown. .
Gavi’s position is that “even considering the unknowns, vaccination remains the best means of protection [contra covid-19], even if vaccines do not guarantee lifelong immunity and reinforcements are needed ”.
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