Publishing their study in the journal Science Immunology this week, the scientists say this gives hope to a 'black cloud' hanging over vaccine development over the duration of its protection.
The study, led by Monash University in Melbourne, shows that specific cells within the immune system - memory B cells - "remember" infection by the virus. If challenged again, they trigger a protective immune response through the rapid production of protective antibodies.
The researchers took a cohort of 25 COVID-19 patients and took 36 blood samples from them from Day 4 post infection to Day 242 post infection.
As with other studies, the researchers found that antibodies against the virus started to drop off after 20 days post infection (such previous studies had pointed to the decline in antibodies as a reason for concern that people may lose immunity quickly).
However, the Monash researchers also looked at the memory B cells: and noted all patients continued to have these cells that recognized one of two components of the SARS-CoV-2 virus, the spike and nucleocapsid proteins. These virus-specific memory B cells were stably present as far as eight months after infection.
They say these results give hope to the efficacy of any vaccine against the virus.
"These results are important because they show, definitively, that patients infected with the COVID-19 virus do in fact retain immunity against the virus and the disease," they said.
"This has been a black cloud hanging over the potential protection that could be provided by any COVID-19 vaccine and gives real hope that they will provide long-term protection."
'Rapid generation of durable B cell memory to SARS-CoV-2 spike and nucleocapsid proteins in COVID-19 and convalescence'
Science Immunology, December 22, 2020. DOI: 10.1126/sciimmunol.abf8891