Invasive Pneumococcal Disease and Long-Term Mortality Rates in Adults, Alberta, Canada

Abstract

D espite introduction and recommendation of the capsular polysaccharide pneumococcal vaccine in Canada during 1989 to persons >65 years of age, Streptococcus pneumoniae is still a cause of major illness and death in Canada and worldwide (1-3). The most serious manifestation of infection is invasive pneumococcal disease (IPD), which is characterized by bacteria invading normally sterile body sites, such as blood, lungs, or cerebrospinal fluid. In Canada, the incidence of IPD is around 8.8-9.9 cases/100,000 persons (4,5) and consistently highest in persons >60 years of age (27.1 cases/100,000 men and 20.2 cases/100,000 women) (6).Short-term 30-day mortality rates after IPD have been frequently studied (estimated case-fatality rate within 30 days ranging from 13% to 21%) (7,8).Increasing age and concurrent conditions are associated with increased case-fatality rates (7,8). However, studies on long-term mortality rates after IPD have been largely deficient, despite IPD being a reportable disease in Canada since 2000 (9).Two studies conducted in Norway and the Netherlands investigated 1-year and 5-year mortality rates after IPD compared with those for age-and sex-matched controls in the general population (7,10). In persons who survived initial hospitalization or survived 30 days after acute infection, IPD mortality rates were higher for cases than for controls (1-year mortality rate 10%-30% for cases vs. 1%-3% for controls; 5-year mortality rate 35%-42% for cases vs. 7%-15% for controls) (7,10). However, the study noted that, in the Netherlands, most deaths occurred within the first 30 days (case-mortality rate 17%) (7). Thus, it remains unclear whether IPD increases long-term mortality rates. Moreover, these were highly selected samples because both studies used data from only 1 hospital in a large urban center, which are unlikely to be representative of the broader IPD population (7,10).Widespread pneumococcal vaccination has seen major success (11). However, with an aging population at risk for IPD, and pneumococcal serotypes changing to evade current vaccinations, IPD remains a disease of public health concern (12). We have shown a change in serotypes and associated potential increases in severity of disease among IPD patients in Alberta, Canada (13). To determine how IPD is affecting mortality rates, we investigated short, intermediate, and long-term mortality outcomes for persons who had IPD compared with age-and sex-matched controls in Alberta over a 20-year period. Methods IPD CasesCommunity cases of IPD were defined by laboratoryconfirmed isolation of S. pneumoniae from a sterile site,

Sex-based difference in immune responses and efficacy of the pneumococcal conjugate vaccine

“…Sex-based differences in the incidence of pneumococcal diseases have been reported, with males across different age groups being more susceptible than their agedmatched female counterparts (20)(21)(22)(23)(24)(25). Additionally, sex-based differences in immune response to PPSV have also been reported in adults, with age influencing those differences (26)(27)(28)(29).…”