The immunogenicity of the new pneumococcal conjugate vaccine in the elderly

INTERVENTION: There are two groups in this study; 1. The control group which received the 23‐ pneumococcal polysaccharide vaccine (23PPV, a dose of 0.5ml‐ Intramuscular injection) 2. The other is the intervention group that received the 7‐valent pneumococcal conjugate vaccine ( PCV7, a dose of 0.5ml ‐ Intramuscular injection) followed by the 23PPV (0.5ml‐ Intramuscular injection) at six months after the first dose. All subjects in the PCV7 arm (i.e. receiving the new vaccine), will also receive 23 PPV six months later as it is normally recommended for all adults aged >65 years and is proven to be effective in preventing the invasive pneumococcal disease (IPD). Therefore, no study subject will be denied the recommended vaccine, and all subjects stand to benefit, as they are unvaccinated at the time of enrolment, and would not have received vaccination otherwise CONDITION: Pneumococcal disease PRIMARY OUTCOME: Immunogenicity (Protein conjugate pneumococcal vaccines are likely to be more ; immunogenic in adults) SECONDARY OUTCOME: Secondary outcome measures : using a subset of 30% of study participants: pneumococcal serotype specific IgG avidity after each dose to assess immunological memory, functional antibody assays using opsonophagocytosis INCLUSION CRITERIA: Hospitalized patients