The strength of the new research is derived from “spike-specific memory b-cells.” For the novel coronavirus (SARS-CoV-2) to effectively infect host cells and replicate its genetic material into them, it needs to bind to spike proteins.
Spike-specific antibodies remained stable in over 90% of the patient sample featured in the new report, between six and eight months.
“Understanding immune memory to SARS-CoV-2 is critical for improving diagnostics and vaccines, and for assessing the likely future course of the COVID-19 pandemic. We analyzed multiple compartments of circulating immune memory to SARS-CoV-2 in 254 samples from 188 COVID-19 cases, including 43 samples at ≥ 6 months post-infection,” the authors of the new study write.
“Spike-specific memory B cells were more abundant at six months than at 1-month post symptom onset. SARS-CoV-2-specific CD4+ T cells and CD8+ T cells declined with a half-life of 3-5 months. By studying antibody, memory B cell, CD4+ T cell, and CD8+ T cell memory to SARS-CoV-2 in an integrated manner, we observed that each component of SARS-CoV-2 immune memory exhibited distinct kinetics.”
Previously conducted research has suggested that natural immunity likely lasts at least six months post-infection.
“Frequent reinfections at 12 months post-infection and substantial reduction in antibody levels as soon as six months post-infection. As protective immunity may be lost by six months post-infection, the prospect of reaching functional herd immunity by natural infection seems very unlikely,” a study from the University of Amsterdam posited back in May.
The vaccines manufactured by Moderna and Pfizer-BioNTech will reportedly have to be administered annually for patients to be properly inoculated. However, early analysis indicates that these doses could offer immunity against COVID-19 for up to three years.
“Most vaccines have their specific duration of immunity that can range from a few months to decades,” Chunhuei Chi, MPH, director of the Center for Global Health at Oregon State University’s College of Public Health and Human Sciences, told verywell health.
“The flu vaccine, which immunizes against seasonal influenza for several months, represents one end of the spectrum; the measles vaccine, which immunizes against measles for life, represents the other. The magnitude of the variation is the result of the unique combination of characteristics of viruses and vaccines.”
So far, public health officials are confident that the vaccine candidates that have passed their clinical trials will be successful against prime coronavirus strains in addition to the more transmissive variants first documented in the UK and South Africa.
More research needs to conducted with respect to the duration of immunity supported by specific doses and the strain detected in Japan over the weekend.
“While immune memory is the source of long-term protective immunity, direct conclusions about protective immunity cannot be made on the basis of quantifying SARS-CoV-2 circulating antibodies, memory B cells, CD8+ T cells, and CD4+ T cells, because mechanisms of protective immunity against SARS-CoV-2 or COVID-19 are not defined in humans. Nevertheless, some reasonable interpretations can be made. Antibodies are the only component of immune memory that can provide truly sterilizing immunity,” the authors concluded in journal science concluded.