The US Centers for Disease Control and Prevention has cautioned immunocompromised individuals that the COVID-19 vaccine may not have been effective for them and also urged them to take precautions as if they have not been vaccinated.

The agency’s website stated that immunocompromised individuals should be guided regarding the potential for diminished immune response to COVID-19 vaccines and must be advised to follow  preventive measures, such as wearing a mask, staying 6 feet away from people they don′t live with, avoiding crowded places and poorly ventilated indoor spaces, in order to protect themselves against the viral illness. The agency is assessing ongoing research looking into the possibility that immunocompromised people could derive benefit from an additional dose of a COVID-19 vaccine… (CNN, July 17, 2021)