Efficacy of pneumococcal vaccination

• polysaccharide pneumococcal vaccine (PPV23) demonstrates variable efficacy; while early trial reviews indicated limited protection against non-bacteraemic pneumonia, bronchitis, or overall mortality in adults (1, 2), subsequent meta-analyses show moderate short-term efficacy (~41% to 70%) against invasive pneumococcal disease (IPD) (1, 7) and some evidence of protection against non-bacteraemic pneumococcal pneumonia in immunocompetent adults (7)
• antibody response wanes significantly over time; PPV23 produces poor antibody responses in children under 2 years of age and reduced responses in individuals with splenic dysfunction or severe immunocompromise (7)
• conjugate pneumococcal vaccines (PCVs) induce superior immunogenicity and immunological memory; they are highly effective in reducing vaccine-type IPD in infants under 2 years of age (3) and are strongly recommended in high-risk populations such as sickle cell disease (4)
• acute otitis media (AOM) prevention remains limited; PCV and PPV administration is not recommended primarily for preventing recurrent AOM, as PCV7 showed only marginal benefit in infants and no benefit in older children with an existing history of AOM (5, 6)

Key Evidence and Policy Context

Adults and Older Populations

• invasive pneumococcal disease (IPD) versus non-bacteraemic pneumonia: PPV23 efficacy is highest for preventing IPD and bacteraemia (50% to 70%) (7); evidence for preventing non-bacteraemic community-acquired pneumonia (CAP) remains moderate to weak, leading to the UK policy shift toward higher-valency conjugate vaccines (PCV20) (7)
• lack of broad mortality benefit: systematic reviews demonstrate no significant reduction in overall all-cause pneumonia or all-cause mortality across general adult populations (1, 2)

Paediatric Populations (Under 2 Years)

• unresponsiveness to polysaccharide vaccines: children under 2 years cannot mount an adequate T-cell-independent immune response to pure polysaccharide antigens (PPV23) (7)
• superiority of conjugate vaccines: T-cell-dependent PCVs (PCV13) elicit robust antibody responses, providing marked reductions in vaccine-serotype IPD and carriage (3, 7)

High-Risk Clinical Groups (Sickle Cell Disease and Asplenia)

• rapid antibody decay: patients with functional or anatomical asplenia suffer rapid antibody decline, necessitating high-potency conjugate coverage and periodic 5-year boosters (4, 7)

Otitis Media Indications

• limited clinical impact: pneumococcal vaccination is not indicated as a standalone strategy for recurrent AOM due to minimal absolute efficacy and serotype replacement by non-vaccine strains (5, 6)

Reference:

1. Dear K, Holden J, Andrews R, Tatham D. Vaccines for preventing pneumococcal infection in adults. Cochrane Database Syst Rev. 2003;(4):CD000422.
2. Huss A et al. Efficacy of pneumococcal vaccination in adults: a meta-analysis. CMAJ. 2009 Jan 6;180(1):48-58.
3. Lucero MG et al. Pneumococcal conjugate vaccines for preventing vaccine-type invasive pneumococcal disease and pneumonia with consolidation on x-ray in children under two years of age. Cochrane Database Syst Rev. 2004 Oct 18;(4):CD004977.
4. Davies EG et al. Pneumococcal vaccines for sickle cell disease. Cochrane Database Syst Rev. 2004;(1):CD003885.
5. Straetemans M et al. Pneumococcal vaccines for preventing otitis media. Cochrane Database Syst Rev. 2004;(1):CD001481.
6. Jansen AG et al. Pneumococcal conjugate vaccines for preventing otitis media. Cochrane Database Syst Rev. 2009 Apr 15;(2):CD001480.
7. UK Health Security Agency (UKHSA). Pneumococcal: guidance and immunisation schedule. UKHSA Guidance. Updated 16 October 2026.