According to a study from China, after a year of COVID-19 infection, the immune system can still continue to remember the virus and show some response on encountering it again.

Researchers in the study, published in  The Lancet Microbe, evaluated 141 people infected with COVID-19 in the first half of 2020. Their blood samples were obtained 12 months later. None of them received a vaccine during the period. Most people were still found to have low levels of antibodies. Most of the people aged below 60 years still had some antibodies which could neutralize the virus. 

In all the participants, irrespective of age or severity of the infection, including those who had lost the neutralizing antibodies, responses by the memory B cells and memory T cells were still seen. Additionally, it was noted that the response was not disrupted by new variants… (Reuters, March 25, 2022)