For adults who have a PPSV23 vaccination recommended 1 year after PCV15, what is the definition of a year? Does it need to be exactly one year? We previously provided PCV15 to some individuals during flu season and told them to get the PPSV23 next year when they get their flu shot. What if they received their flu shot in November last year, but return for their flu shot in October this year?

What you describe is a good strategy for administration of pneumococcal vaccines to people age 65 years and older. ACIP does not define “one year” but this is assumed to be one calendar year. Receiving PPSV23 a few days or weeks earlier than one calendar year after PCV13 or PCV15 is not a medical problem. However, it could be a problem for reimbursement since Medicare will only pay for both a PCV vaccine and a PPSV23 vaccine if they are given at least 11 months apart. Private insurance may have similar rules. Here is the wording from the Centers for Medicare and Medicaid (CMS): “An initial pneumococcal vaccine may be administered to all Medicare beneficiaries who have never received a pneumococcal vaccine under Medicare Part B. A different, second pneumococcal vaccine may be administered 1 year after the first vaccine was administered (i.e., 11 full months have passed following the month in which the last pneumococcal vaccine was administered).”