Vaccine 25 (2007) 4767–4774 Comparative reactogenicity and immunogenicity of 23 valent pneumococcal vaccine administered by intramuscular or subcutaneous injection in elderly adults Ian F. Cook ∗ , Dimity Pond, Gunter Hartel University of Newcastle, Callaghan, NSW, Australia Received 6 October 2006; received in revised form 24 March 2007; accepted 9 April 2007 Available online 26 April 2007 Abstract 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 g/ml, odds ratio 22.4 (8.06–74.84) compared with pre-vaccination antibody titre <1 g/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. © 2007 Elsevier Ltd. All rights reserved. Keywords: 23 Valent pneumococcal vaccine; Elderly; Intramuscular; Subcutaneous 1. Introduction Infection with Streptococcus pneumoniae is responsible for significant morbidity and mortality worldwide, especially in the very young, the elderly and those with predisposing risk factors [1,2]. The magnitude of this disease has prompted an interest in its control through vaccination. Successful quadri- valent and pentavalent vaccines were prepared in the 1940s [3,4] but these were withdrawn by 1949 due to the advent of penicillin. However, the emergence of penicillin-resistant pneumococci [5] has shifted the focus of disease management again to the prevention of infection through vaccination. ∗ Corresponding author at: 387 Schubach Street, Albury, NSW 2640, Australia. Tel.: +61 2 60235409. E-mail address: drifcook@bigpond.com (I.F. Cook). A 14 valent polysaccharide vaccine was licensed in 1977 [6] and this was replaced by a 23 valent vaccine in 1983. The latter vaccine covers at least 90% of serotypes responsible for invasive pneumococcal disease in developed and developing countries [7]. Prospective clinical trials [8,9] with 23 valent pneumo- coccal vaccine have failed to demonstrate its efficacy with this being attributed to inadequately sized study populations [10]. However observational studies using case control, indi- rect and retrospective cohort designs have observed a 50–80% vaccine effectiveness [11] with pneumococcal bactereraemia as the outcome measure. Limitations of this vaccine have not been overcome by conjugating the polysaccharide antigens with carrier pro- teins [12], as has occurred with Haemophilus influenzae type b [13]. Future pneumococcal vaccines will probably 0264-410X/$ – see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.vaccine.2007.04.017