Various previous studies have shown that immunity against covid-19 can last for around six months.
The study, led by scientists at La Jolla Institute for Immunology at San Diego university in the United States, assessed elements of the immune response including antibodies and T-cells, and found the "immune memory" may last for at least eight months. Another study from researchers at the University of Washington indicates that immunity lasts for at least three months.
And it could mean that protection conferred by COVID-19 vaccines made by Pfizer and Moderna, which are both more than 90 percent effective at preventing infection, according to early data will last longer than previously thought - although neither company has had a chance to prove that, yet. The researchers said that there was about a 200-fold range in the level of antibody responses among the adults. The researchers said there appeared to be an increase in memory B cells over time.
The scientists detected B cells in nearly all covid-19 cases.
T cells come in two forms: one that group that works alongside B cells to manufacture the right antibodies to fight a given pathogen and a second type that acts like an assassin, killing off once-healthy cells that have become infected, so that they can't help a virus, bacterium or even cancer spread elsewhere. Antibodies, after all, are just one facet of the body's complex immune system, and the new study indicated that other factors like T cells showed only a slight decay several months out from infection, while B cells, which produce new antibodies as needed, had actually grown in number in most participants.
Not only is the study under question backed with evidence, but it may also be another green light we have in our fight against COVID-19 and resume life back to normalcy. "The spike IgG titers were durable, with modest declines in titers at six to eight months".
Scientists had feared that those who developed only mild infections would be unlikely to have a strong immune response, but nearly all developed cells capable of creating new antibodies if they encountered the virus again.
In this study, a research team at the Medical Center - University of Freiburg in Germany found that after recovery from SARS-CoV-2 infection, immune cells are formed which remain in the body and could mediate a rapid immune response in case of reinfection. And while there have been cases of reinfection, they seem to be rare, per the Times.
"By studying these multiple compartments of adaptive immunity in an integrated manner, we observed that each component of SARS-CoV-2 immune memory exhibited distinct kinetics", the researchers wrote in the study.
In contrast, the viral loads of SARS and MERS peaked at 10-14 days and seven to 10 days after symptom onset respectively, explaining why transmission of these viruses can be effectively reduced by immediate identification, isolation and quarantine of people who show symptoms.