Preventability of invasive pneumococcal disease and assessment of current polysaccharide vaccine recommendations for adults: United States, 2001-2003

Background. To prevent Streptococcus pneumoniae infection among persons at highest risk for invasive pneumococcal disease ( IPD), the pneumococcal polysaccharide vaccine ( PPV) is currently recommended for persons >= 65 years old and persons 2 - 64 years old with certain underlying conditions. Policymakers have considered expanding recommendations for PPV to include persons who are 50 - 64 years old and additional populations at risk for IPD. Our objectives were to determine the proportion of IPD cases that might have been prevented if all persons with vaccine indications had been vaccinated and to evaluate new indications. Methods. From 2001 to 2003, we performed a case series study of IPD in adults at 6 sites of the Active Bacterial Core surveillance - Emerging Infections Program Network. A case of IPD was defined as isolation of pneumococcus from a normally sterile site from a resident of 1 of the surveillance areas. Results. Among 1878 case patients, 1558 ( 83%) had at least 1 current vaccine indication; of these, 968 case patients ( 62%) were unvaccinated. Adherence to existing vaccine recommendations would have prevented 21% of all cases. The proportions of all cases potentially prevented by each new indication were as follows: lowering the universal age of recommended vaccination to 50 years, 5.0% - 7.0%; adding new risk- based indications to include current smoking, 1.5% - 2.5%; former smoking, 0.4% - 0.7%; black race, 1.0% - 1.4%; and asthma, 0.3% 0.4%. Conclusions. Increasing vaccine coverage rates among persons with a current indication may prevent more cases than expanding existing indications. Of the potential new indications studied, the strategy that may prevent most cases is lowering the recommended age for universal vaccination to 50 years.