SINGAPORE: Over the weekend, the Ministry of Health (MOH) reported Singapore’s first likely case of reinfection, a Bangladeshi migrant worker who had tested positive for COVID-19 again after recovering from the disease last year.
The 28-year-old work permit holder, who lives in a dormitory at 43 Tech Park Crescent, first tested positive on Apr 12 last year as part of the cluster of infections there.
He recovered and tested negative for COVID-19 but on Jan 25, the man was confirmed to have COVID-19 again after being detected through rostered routine testing.
MOH said that the virus detected in his samples taken in January this year was "genetically distinct from that associated with the dormitories outbreak in 2020, suggesting that this is likely a different and new infection", adding that reinfection is "rare".
Singapore now joins a list of places that have reported cases of reinfection, with the first documented case involving a 33-year-old man in Hong Kong in August last year.
READ: Singapore reports first likely COVID-19 re-infection after Bangladeshi dorm resident tests positive again
Here's what we know so far about COVID-19 reinfection:
WHAT IS THE LIKELIHOOD OF COVID-19 REINFECTION?
Studies have suggested that reinfection among most recovered patients is unlikely for at least six months.
A study conducted at the UK Biobank indicated that a vast majority of people retain detectable COVID-19 antibodies for at least that period following an infection.
The study looked at levels of previous COVID-19 reinfection in populations across Britain, as well as how long the antibodies persisted in those who were infected.
Of the participants who tested positive for COVID-19 infection, 99 per cent had retained antibodies for the SARS-CoV-2 virus for three months, the results showed. After six months, 88 per cent still had them.
Another British study on frontline healthcare workers, conducted by researchers at the University of Oxford, made similar findings.
The study, which was reported in November, also suggested that cases of reinfection is “likely to remain extremely rare”.
"Being infected with COVID-19 does offer protection against reinfection for most people for at least six months," said David Eyre, a professor at Oxford's Nuffield Department of Population Health.
"We found no new symptomatic infections in any of the participants who had tested positive for antibodies."
The findings should offer some reassurance for the millions of people worldwide who have been infected with the virus, said the researchers at the University of Oxford.
In the case of the Bangladeshi worker in Singapore, he tested positive for the virus on Jan 25, six months after he was cleared.
MOH said it will continue to closely monitor recovered cases to determine their post-infection immunity and that there are currently no indication that recovered workers have significant loss of post-infection immunity.
HOW MANY CASES OF REINFECTION HAVE BEEN REPORTED?
Cases have been reported in several places, including Hong Kong, the United States, Netherlands and Belgium.
The first documented case, the 33-year-old man from Hong Kong had tested positive again four-and-a-half months after being first confirmed to have the disease.
He was cleared and discharged from a hospital in April last year but tested positive again after returning from Spain via Britain on Aug 15.
One case each in Belgium and in the Netherlands were reported shortly after.
ARE REINFECTION CASES MORE SEVERE?
According to a study published in The Lancet Infectious Diseases journal, patients who contract the virus a second time may experience more severe symptoms from their initial infection.
This was the case for a 25-year-old man from Nevada, who experienced mild illness when he first tested positive in April last year, but developed more severe symptoms when he got sick again in May.
The 33-year-old in Hong Kong, however, remained asymptomatic both times.
Both men were said to have contracted a different strain of the virus the second time they were infected.
In October, the Netherlands Institute for Public Health confirmed that an 89-year-old Dutch woman had died after being reinfected with the SARS-CoV-2 virus. The woman had previous health complications and is believed to be the world's first COVID-19 reinfection death.
The Bangladeshi migrant worker in Singapore reportedly felt unwell on Jan 22 and 23, but is otherwise asymptomatic, reported MOH.
SHOULD I TAKE THE VACCINE IF I HAVE ALREADY RECOVERED FROM COVID-19?
Even if you have recovered from COVID-19, you should still take the vaccination when it is available: That's the message the US Centers for Disease Control and Prevention (CDC) has for those who have been cleared of the virus.
It recommends all to get vaccinated due to the “severe health risks associated with COVID-19” and warned that there is still the possibility of reinfection.
“The immunity someone gains from having an infection, called natural immunity, varies from person to person,” CDC said in an advisory on its website.
“Some early evidence suggests natural immunity may not last very long.”