On Sept. 4, 2015, the U.S. Centers for Disease Control and Prevention’s (CDC) Advisory Committee on Immunization Practices (ACIP) published updated recommendations regarding the intervals between PCV13 and PPSV23 vaccines for use in immunocompetent adults age 65 years and older.

The CDC recommended that a dose of PCV13 be followed by a dose of PPSV23 in all adults aged ≥65 years who have not previously received pneumococcal vaccine and in persons aged ≥2 years who are at high risk for pneumococcal disease because of underlying medical conditions. The recommended intervals between PCV13 and PPSV23 given in series differ by age and risk group and the order in which the two vaccines are given.

Studies evaluating the immune response to a conjugate vaccine (PCV7 or PCV13) followed by the polysaccharide vaccine (PCV–PPSV23 sequence) at intervals of 2, 6, or 12 months or 3–4 years demonstrated that following the PPSV23 dose, antibody levels against serotypes common to both vaccines were higher than the pre-PCV baseline. Eight studies compared immune responses among immunocompetent adults aged ≥50 years after a PCV–PPSV23 sequence with responses following PCV or PPSV23 administered alone. Four studies showed that antibody responses (measured by opsonophagocytic activity [OPA] or immunoglobulin G [IgG] levels or both) following PCV7–PPSV23 doses given 6 months apart were better than or equivalent to responses following PCV7 or PPSV23 alone for most pneumococcal serotypes measured.

Another study showed that a 1-year interval between receipt of conjugate vaccine and polysaccharide vaccine (PCV7–PPSV23 sequence) also led to improved immune responses compared with those following a single PPSV23 dose (13). Comparison of antibody responses after a PCV13–PPSV23 sequence to responses following PCV13 or PPSV23 alone, across two studies with intervals of 1 year and 3–4 years between the two vaccines, indicated that the responses to a larger number of serotypes are improved with a 3–4 year interval compared with a 1-year interval. One study among pneumococcal vaccine–naïve Alaska Native adults aged 55–70 years included direct comparison between intervals of 2 months and 6 months between receipt of PCV7 and PPSV23. No differences in the immune responses were observed; however, the group with a 2-month interval between doses reported more injection site swelling than the group with a 6-month interval.

In summary, these studies of PCV–PPSV23 sequence among immunocompetent adults suggest that 1) shorter intervals (e.g., 8 weeks), may be associated with increased local reactogenicity when compared with longer intervals, and 2) longer intervals (e.g., ≥1 year) may lead to an improved immune response against serotypes in both vaccines compared with a single dose of PCV13 or PPSV23. Additionally, changing the recommended interval for the PCV13–PPSV23 sequence to ≥1 year would allow the recommended interval for immunocompetent adults aged ≥65 years to be the same, regardless of the order in which the two vaccines are given (Box).