Comparative reactogenicity and immunogenicity of 23 valent pneumococcal vaccine administered by intramuscular or subcutaneous injection in elderly adults.

23 Valent pneumococcal vaccine is provided to the elderly through public health programs in many countries. However there is no clear recommendation regarding its route of administration (subcutaneous or intramuscular). In a randomised, observer blind study of 254 elderly subjects, the immunogenicity of a 23 valent pneumococcal vaccine was not influenced by its route of administration. A low rate of systemic adverse reactions was observed with the vaccine (subcutaneous and intramuscular both 6.3%). Local adverse reaction rates were; intramuscular 7.1% and subcutaneous 18.9% and these were predicted by: * Pre-vaccination antibody titres>1 microg/ml, odds ratio 22.4 (8.06-74.84) compared with pre-vaccination antibody titre<1 microg/ml. * Female gender, odds ratio 5.0 (1.85-14.83) compared with male gender. * Subcutaneous injection route, odds ratio 3.20 (1.13-9.13) compared with intramuscular injection route. * Female gender subcutaneous injection route, odds ratio 2.99 (1.10-8.70) compared with female gender intramuscular injection route. These data support the intramuscular injection of 23 valent pneumococcal vaccine, especially in elderly females.