The World Health Organization (WHO) welcomed the finding by ensuring that it broadens its understanding of coronavirus immunity.
"Filing in the U.S. represents a critical milestone in our journey to deliver a COVID-19 vaccine to the world and we now have a more complete picture of both the efficacy and safety profile of our vaccine, giving us confidence in its potential", Pfizer CEO Albert Bourla said in a statement.
"This is really good news, because we can be confident that, at least in the short term, most people who get COVID-19 won't get it again", David Eyre of the University of Oxford's Nuffield Department of Population Health was quoted as saying.
There have been concerns that the immunity produced after treatment of coronavirus could be short-lived and that the recovered patient may get sick again.
But the results of the study, conducted on a group of United Kingdom healthcare professionals - who are among the most at risk of compromising COVID-19 - indicate that relapse cases are rare.
Researchers at Oxford studied healthcare workers for 30 weeks since April.
In addition, 76 staff members without antibodies tested positive for COVID-19, but did not have outward symptoms of the disease, while three of those with antibodies remained asymptomatic, according to the researchers.
Its results have not peer-reviewed by other scientists but were published before review on the MedRxiv website.
"We know from a previous study that antibody levels fall over time", Eyre said.
Also read: Coronavirus: why are the "false positives" of Covid-19 also important?
New York, Nov 20 (SocialNews.XYZ) Researchers have now claimed that pregnant women, who test positive for Covid-19, their newborn babies have a low risk of developing severe symptoms.
"Our findings are that approximately five percent of all delivered women with Covid-19 infection develop a severe or critical illness", said study author Emily Adhikari from the UT Southwestern Medical Centre in the US.
France surpassed Russian Federation to become the worst-affected country in the region, ranking only behind the United States, India and Brazil.
India's total number of coronavirus cases crossed the 9 million mark on Friday, with the capital New Delhi continuing to report rising cases despite a country-wide downward trend of daily infections.
More than 51 million people worldwide have been infected with Kovid-19.