A "STERILISING immunity" that prevents the SARS-CoV-2 virus from infecting the human respiratory tract is the most desirable form of protection against Covid-19, said a virologist.
However, she said, there was no scientific evidence yet to suggest that either vaccines or post-infection recovery could confer long-term "sterilising immunity" on people.
Natural infections, said Associate Professor Dr Chee Hui Yee, were able to elicit mucosal immunity, which protects people from being re-infected with Covid-19 for a short period of time after recovery.
"Mucosal immunity plays a pivotal role in the early restriction of viral replication, the clearance of SARS-CoV-2 virus, and to prevent transmission of SARS-CoV-2.
"In contrast, immunisation via intramuscular vaccines will elicit systemic immunity that only prevents against severe disease and mortality.
"Mucosal immunity, therefore, protects a person from being re-infected, but only for a short period of time after recovery.
"However, only sterilising immunity can completely block transmissions and prevent Covid-19 infections.
"The vaccines available now are unable to grant this type of immunity yet," she told the New Straits Times.
As such, Dr Chee said Malaysia must continue to enforce a face mask mandate, despite the country's high vaccination coverage and increasing booster uptake.
"Wearing a face mask is particularly important for us to protect children below 5 who are not eligible for vaccination yet."
Her response came after the SFGATE news portal said fully-vaccinated people developed "immunity superpowers" if they had been infected by Covid-19.
The report, published on Friday, cited two experts from the University of California, San Francisco.
They claimed those who had recovered from post-vaccination infections might not even need to wear face masks.
Professor Dr G. Jayakumar, a community and occupational medicine professor at the Manipal University College Malaysia, said a face mask mandate was still relevant until the World Health Organisation (WHO) announced a state of endemicity.
"Wearing a face mask is also relevant if people have compromised immunity or live with someone who does have such condition.
"Wearing a mask and maintaining social distance are advisable around strangers, especially in indoor areas with standing air where the virus may accumulate.
"Over time, healthy people may discard the habit of wearing masks when endemicity has been announced," he said.
While recent studies are optimistic about the protection gained from natural infection, Dr Jayakumar said acquired immunity, obtained through vaccination, was a more preferred and safer option.
"Fully vaccinated persons are less likely to suffer from severe Covid-19 infections.
"Vaccination also greatly reduces the risk of hospitalisation and fatalities while breakthrough infections from mutations are likely to be asymptomatic.
"The risk of contracting and dying from Covid-19 is extremely small in a vaccinated population.
"In fact, the risk of dying in a road traffic accident is much higher in Malaysia," he said.
Epidemiologist and biostatistician Professor Dr Jamalludin Ab Rahman said vaccination could indirectly reduce transmissions since fully vaccinated people were able to shed the virus faster than unvaccinated ones.
"However, just like many other viral infections, immunity against Covid-19 could be specific to a particular viral strain.
"This means that immunity obtained against one variant may not be able to protect people against another variant."
Dr Jamalludin said: "In my view, it is better to gradually lift restrictions, such as the face mask mandate, rather than having to reinstate restrictions after revoking them."