At least three people were infected with COVID-19 a second time this week, asking what we know about immunity to the deadly virus.
While past infections have been reported in the past, including some in South Korea in May, it later emerged that the cases were likely a result of false positives in testing.
But the new cases are much more plausible – and more concerning to some scientists.
The new cases were confirmed with strict genetic tests and also showed a slightly different strain of the virus, which one scientist called “bad news”.
Where are the confirmed cases of reinfection of COVID-19?
In the Netherlands, an elderly person with a weakened immune system was re-infected with the coronavirus, health officials confirmed Tuesday, according to Sky News.
A second European patient, from Belgium, was also re-infected in mid-June after first catching the virus in March, the outlet reported.
Not much else is known about the names, ages or situations of the patients.
The European cases come after investigators on Monday revealed a 33-year-old Hong Kong man was the first patient ever confirmed to be re-infected with the coronavirus, according to the New York Times.
The apparently young and healthy patient first became ill with a mild case of the virus in March and is testing positive again at an airport this month after returning from a trip to Spain, according to researchers from the University of Hong Kong.
Is COVID-19 re-infection dangerous and can you develop immunity?
In the case of the Hong Kong man, scientists said that although the previous infection did not prevent him from recovering COVID-19, his immune system probably kept the virus under control for the second time.
“The second infection was completely asymptomatic – his immune response prevented the disease from getting worse,” Akiko Iwasaki, an immunologist at Yale University, told The New York Times. “It’s kind of an example of a textbook on how immunity should work.”
She added: “Natural infection provided immunity that prevented disease but not reinfection.”
Doctors also report that the patient from Belgium had only mild symptoms after he contracted the virus again.
Although some scientists said that reinfections were “expected”, the new cases raised concerns in the scientific community about immunity to the disease.
“I think we will see other similar stories in the coming days. These may be exceptions, but they exist. It is not good news,” Belgian virologist Marc Van Ranst told NBC.
There is currently no evidence that people who have recovered from COVID-19 and have antibodies are protected against a second infection, according to the World Health Organization.
How long do antibodies last?
COVID-19 is still too new for scientists to know the answer to that question. But the Hong Kong man was re-infected about four months after first contracting the virus. The patient from Belgium picked it up again three months later.
According to Van Ranst, more people could experience a COVID-19 reinfection “after six or seven months”.
By comparison, a person can be re-infected with the common cold in less than a year, but experts had hoped that the new coronavirus would behave better than SARS and MERS – which produce antibodies that last for several years.
What does this mean for a COVID-19 vaccine?
Scientists do not know it yet. But if the coronavirus mutates faster than expected, people will often need to get vaccinations – similar to the way flu shots are distributed, New York Times scientific writer Donald McNeil suggested on the podcast The Daily.
Where else have there possibly been COVID-19 reinfections?
Doctors have reported several cases of suspected reinfection in the United States – including in Los Angeles and New Jersey. South Korea has also reported cases of suspected rainfall.
However, none of these cases have been confirmed by rigorous genetic testing.
.
