Indications for Pneumococcal Vaccine Adults age 65 years or older who have not previously received a pneumococcal conjugate vaccine or whose vaccination history is unknown should receive either 1 dose of PCV20 or 1 dose of PCV15 followed by a dose of PPSV23 Adults 19 to 64 years who have certain medical conditions or other risk factors (see below) who have not previously received a pneumococcal conjugate vaccine or whose vaccination history is unknown should receive either 1 dose of PCV20 OR 1 dose of PCV15 followed by a dose of PPSV23 For both age groups, the dose of PPSV23 should follow the dose of PCV15 by at least 1 year.