Persistence of immunity to conjugate and polysaccharide pneumococcal vaccines in frail, hospitalised older adults in long-term follow up.

BACKGROUND

Data on long-term antibody responses to pneumococcal vaccines in the elderly, especially the frail elderly at greatest risk of severe disease, are limited. We followed up participants in a randomised trial of the immunogenicity of 23-valent polysaccharide vaccine (23vPPV) and 7 valent pneumococcal conjugate vaccines (PCV7) in hospitalised older adults.

METHODS

We measured antibody to vaccine serotypes by standardised enzyme-linked immunosorbent assay (ELISA) and opsonophagocytic (OPA) assays. A follow up study was conducted six years after vaccination with 23vPPV alone or with PCV7 followed by 23vPPV six months later.

RESULTS

Of 215 surviving trial participants, 136 (63%) completed follow up; 62 received 23vPPV and 74 received PCV7 + 23vPPV. There was no significant difference in death and readmission between arms. Antibody levels by ELISA and OPA did not differ significantly between the two study arms at 72 months post-vaccination. ELISA and OPA antibody remained higher than baseline except for OPA antibody to 4, 6A, 6B, 9v, 19F and 23F, including in subjects with undetectable immunity at baseline.

DISCUSSION

While ELISA responses in both study arms remained high 6 years post-vaccination, considerable waning was observed by OPA in both study arms, which should be considered given the current single-dose recommendation in Australia. Further research is needed to inform pneumococcal vaccine recommendations in people over the age of 65.