Covid-19 survivors are not safe from another infection because the antibodies wane over time. But the immune system has a durable memory of the virus.
A study by scientists at the University of Pennsylvania said that the booster shots with mRNA vaccines prove that the immune system has a durable immune memory to SARS-CoV-2 in the form of B and T cells that increased over time to help ward off serious illness, reported Bloomberg.
John Wherry, director of the Institute for Immunology, said that their observation in 61 people was surprising as it found out that the body has its own natural support to defend it against Covid-19 even when the antibody levels decline.
If antibodies wane in the body and you are infected, the memory B cells will either renew or respond rapidly to make new neutralising antibodies, said the peer-reviewed research.
The group also found high levels of vaccine-induced T cells maintaining an additional protective armour even after six months. T cells are a type of white blood cell capable of finding and killing virus-infected cells.
U.S. President Joe Biden had said that his administration is considering a third dose of vaccine five months after receiving a second dose. Many experts are concerned about Covid vaccines providing a weaker defence against the more transmissible delta strain. Countries that began vaccination before Delta emerged as a dominant variant are considering a booster shot.
Researchers found that the memory B cells generated by the mRNA vaccines made by Moderna Inc. and Pfizer Inc. are better at blocking virus variants including alpha, beta, and delta. They are better than the antibodies produced in response to a mild case of Covid-19, reported Bloomberg.
Wherry added that the findings of the new research suggest that more people need to get vaccinated.