At this point we don’t know if additional booster doses, beyond the now recommended or available third dose, will be needed. Booster doses are common for many vaccines. The scientists and medical experts who developed the COVID-19 vaccines will continue to closely watch for signs of waning immunity, how well the vaccines protect against new mutations of the virus, and how that data differ across age groups and risk factors. It is possible that the current booster dose could result in long lasting immunity or alternatively that additional booster doses might be needed in the future, and scientists will be carefully monitoring that issue.
Added November 22, 2021