COVID-19 Vaccine Protective Immunity Could Exceed Six Months

A research article published by the American Association for the Advancement of Science on January 6, 2021, stated 'understanding immune memory to the SARS-CoV-2 betacoronavirus is critical for improving diagnostics and vaccines, and for assessing the likely future course of the COVID-19 pandemic.'

These researchers 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.

They found IgG to the Spike protein was relatively stable over 6+ months. And spike-specific memory B cells were more abundant at 6 months than at 1-month post symptom onset.

Furthermore, SARS-CoV-2-specific CD4+ T cells and CD8+ T cells declined with a half-life of 3-5 months.

The researchers concluded by saying: 'While immune memory is the source of long-term protective immunity, direct conclusions about protective immunity cannot be made based on 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.'