Pneumococcal infections can cause serious morbidity and mortality, especially in the elderly population and patients with chronic illness.Important evidence showed that the majority of mortality during the 1918 Spanish Flu pandemic and also the recent H1N1pdm2009 was associated with pneumococcal coinfection.In Hong Kong, the overcrowded living conditions facilitate the transmission of both influenza and pneumococcal infection.Vaccination is the only public health measure likely to reduce the serious burden of pneumococcal diseases.In Hong Kong, both the 23-valent pneumococcal polysaccharide vaccine (PPV23) and the 13-valent pneumococcal conjugate vaccine (PCV13) are available for the adults.PPV23 has been shown to reduce the rates of community-acquired pneumonia hospitalization and death in the elderly in the short term.Despite international recommendations, the uptake of PPV23 has varied greatly among countries.Moreover, uncertainty about the value of pneumococcal polysaccharide has increased in recent years because the use of PCV in children has reduced the incidence of IPD caused by PCV serotypes in older adults due to herd immunity.Recent studies have suggested that revaccination with PPV23 is associated with hyporesponsiveness.This raised questions whether PCV13 should replace PPV23 for public health vaccination program, especially for the elderly and immuncompromised.Effective protection against pneumococcal disease requires monitoring the changing epidemiology of pneumococcal serotypes causing IPD and improving vaccine coverage.For elderly adults, it will be critically important for pneumococcal vaccination recommendations to be based on comparative evaluation of PPV23 and the new PCV13 with regard to their long-term immunogenicity, clinical and cost effectiveness.