Though the scientific community is mulling over whether the Covid-19 reinfection cases are possible, Bangladeshi scientist Dr Bijon Kumar Shil rules out the chances.
"There's no possibility of a second time infection as antibody develops naturally in the body with recovery from the virus," Dr Bijon, head of the microbiology department at Gono Bishwabidyalay, told The Daily Star.
The molecular immunologist insisted that a few reports on reinfection were not based on evidence, claiming that his own research at the university laboratory also found no link as yet.
Some researchers do theorise that there is still not enough scientific information to assess how long the antibodies in the body following a Covid-19 infection can provide protection.
A study published in Nature Medicine journal on June 18 created quite some debate, when researchers from Chongqing Medical University tested 37 individuals previously infected with Sars-Cov-2, and found that there was a significant reduction in the IgG antibody levels of a majority of the participants.
IgG antibodies, also called Immunoglobulin (G), is an antibody created by white blood cells called lymphocytes as a delayed response to a pathogen. It is also longer lasting than other antibodies created during the early stages of infection.
On the other hand, SARS-CoV-1, the virus that caused the SARS outbreak between 2002 and 2004, produced antibodies that could last up to two years, researchers from China's Institute for Viral Disease Control and Prevention found in 2007.
"Three types of antibodies are created -- first, IgA, then IgM, and lastly IgG. For certain viruses of the coronavirus family, the IgA stays in the body for 50 days. IgM stays for between 5 to 6 months, and the IgG stays for about 2 years. A Covid-19 infected body should create either two or all the three of these antibodies," said Dr Bijon a few days back.
The eminent immunologist was instrumental in developing testing kit for SARS while working at a Singapore lab back in 2003.
"Covid-19 has 82 percent similarity with that of SARS. So, in a way, novel coronavirus is not exactly new to me," he said.
"And, from my experience and research, I'm almost certain that reinfection is not possible."
He, however, added that more research is needed into how infection is happening in Bangladesh. "There has not been any specific research into reinfection in the country."
The researcher also spoke about memory cells and how they will act.
"Even if the body's antibodies vanish, memory cells are created in the body. If the body gets attacked by the same virus, the body remembers and the memory cells start producing antibodies. For the first infection, the body can take up to 10 days to produce antibodies. The second time, the time needed to produce antibodies is drastically reduced. Even if anyone does get re-infected, the health risks might not be as severe," he said.
"Research around the world is yet to find evidence of reinfection," he added, although research has found diminishing antibody levels.
In May 19, South Korea reported cases of "reinfection" but later on Korea Centers for Disease Control and Prevention found that 350 of those people tested "false positive".
"They had dead viral RNA in their blood, which showed up in the PCR process. That is how those tests came back positive," explained Dr Bijon.
He was asked about the cases of two Bangladeshi health workers who supposedly got "reinfected" as media reported.
"There has not been any specific research into the reinfection of those two health workers but one cannot rule out the possibility of wrong test results. Perhaps they received a false positive during the first test or a false negative during the second test, when they thought they were cured. And so they tested positive the third time," said Dr Bijon.
He reiterated the need for more research, saying misinformation regarding reinfection is being reported in the media since there is not enough Bangladesh-specific research.