Now that a second booster dose has been recommended for certain groups, people (ages 12 years and older if they received the Pfizer-BioNTech series, or ages 18 years and older if they received the Moderna series) who are moderately or severely immunocompromised may now receive five doses total (a primary series of three doses, plus two booster doses). People who are moderately or severely immunocompromised—and who received a single J&J/Janssen COVID-19 vaccine primary series—are now able to receive a total of four vaccine doses: one J&J/Janssen dose, one additional mRNA dose and two booster doses.