While the Covid-19 cases across the globe continue to surge, the majority of people are expected to have 'mild' Covid symptoms that usually resolve at home.
Scientists have shown that mild novel coronavirus infection leaves behind some significant changes in the immune system.
According to a new study, people who have had mild illness due to Covid-19 develop antibody-producing immune cells that can last a lifetime and provide them with defence against the virus.
Researchers at Washington University in St. Louis, US, discovered that after a viral outbreak, antibody-producing immune cells replicate and accumulate in the blood, causing antibody levels to reach a new high.
Most of these cells die and blood antibody levels drop once the infection is resolved.
However, a small group of antibody-producing cells known as long-lived plasma cells migrate to the bone marrow and settle down, secreting low levels of antibodies into the bloodstream to help protect against another virus experience.
Associate Professor at the varsity's School of Medicine said, 'We found antibody-producing cells in people 11 months after the first symptoms.
People who have had mild illness due to Covid-19 develop antibody-producing immune cells that can last a lifetime and provide them with defence against the virusThese cells will live and produce antibodies for the rest of people's lives.
For the study published in the journal Nature, the team recruited 77 patients for the trial, with antibody levels in blood samples measured at three-month intervals beginning around a month after initial infection.
Seven or eight months after their initial illnesses, the researchers retrieved bone marrow from 18 of the patients. In addition, the scientists obtained bone marrow from 11 individuals who had never contracted coronavirus.
15 of the bone marrow samples contained antibody-producing cells that were unique to the virus that causes Covid-19.
Four months later, those cells could already be identified in the five individuals who returned to provide a second bone-marrow examination.
There were no such antibody-producing cells in the bone marrow of the 11 individuals who had never had Covid-19.
Praveen Gupta, director and head, neurology, Fortis Memorial Research Institute, Gurugram said, 'It has also been shown that the reinfection rate of people already having a mild infection is only two per cent which is very less."
"Based on this fact the principle of herd immunity was developed if a large number of people will get a mild clinical infection that will lead to the development of herd immunity," he said.