On May 24, 2021, Pfizer announced that the first enrolled subjects had received their immunizations as part of a new study in adults ages 65 or older exploring the coadministration of the companyﾒs 20-valent pneumococcal conjugate vaccine (20vPnC) candidate following a booster dose of the Pfizer-BioNTech COVID-19 Vaccine, currently authorized by the Food and Drug Administration under an Emergency Use Authorization.

The primary objective in the trial was to describe safety when both vaccines are co-administered, with follow up six months after vaccination. Secondary objectives are to describe immune responses produced by each of the vaccines.