Impact of the introduction of pneumococcal conjugate vaccine on rates of community acquired pneumonia in children and adults
Introduction
Pneumococcal protein polysaccharide conjugate vaccines have both direct and indirect, or “herd,” benefits. Vaccination of infants greatly reduces their risk of vaccine-type invasive pneumococcal infection and also decreases their risk of all-cause radiographically confirmed pneumonia [1], [2], [3]. Vaccination also decreases nasopharyngeal carriage of vaccine serotype pneumococci [4], [5], interrupting transmission of those strains from vaccinated persons to others. Consequently, rates of invasive pneumococcal disease in adults have declined significantly following the introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) into the routine childhood immunization schedule in the United States [6], [7], [8], [9], [10].
Since Streptococcus pneumoniae is an important cause of community-acquired pneumonia (CAP) in adults [11], [12], [13], it is also possible that PCV7 use in children reduces CAP risk in adults. If so, the public health benefit derived from vaccinating infants with PCV7 would be substantially higher than currently recognized. Pneumonia is a difficult outcome to study, however. A common outcome ascertainment method is to define CAP using International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) diagnosis codes that are assigned to medical encounters and available in large health care utilization databases. However, in a previous randomized clinical trial in children, a vaccine effect was not found when pneumonia was defined by diagnostic codes but was observed when validation was performed and a more specific outcome definition obtained [14]. Similarly, although validation in a large, observational surveillance setting is challenging due to the large investment of resources required, it may be necessary to ensure the correct detection of effects.
To determine whether pneumonia rates have declined following the introduction of PCV7 for infants, we used ICD-9 codes to identify presumptive outpatient and hospitalized episodes of CAP among the members of Group Health from 1998 through 2004, a period spanning years before and after the introduction of PCV7 for infants in 2000. To improve our ability to detect a change in pneumonia rates if present we validated, to the extent possible, the presumptive pneumonia events identified among the 794,282 persons enrolled in Group Health at any time during this 7-year period.
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Study population and setting
We defined a retrospective cohort of children and adults enrolled in Group Health, a health maintenance organization in Washington State, at any time from the January 1, 1998 study start date through the December 31, 2004 study end date. Demographically, about half (54%) of Group Health enrollees are female and most (about 85%) are Caucasian. Cohort members were followed from the study start date, their enrollment date, or birth date (whichever is latest) until the study end date, their
Characteristics of the study population
During the study period, 794,282 individuals contributed 2.52 million person-years of observation (Table 1). Infants (≤2 years), older children (3–17 years), young adults (18–64 years), and seniors (65 years and older), respectively, contributed 3%, 19%, 64%, and 14% of the total study person-time. Both males and females contributed approximately half of the total study person-time. Among adults, about 14% were current smokers and 60% had no chronic conditions (including congestive heart
Discussion
In this comprehensive, population-based evaluation, we found no consistent evidence for a decline in CAP rates in adults following the introduction of PCV7 for infants. The findings did not change when we evaluated different age groups, confirmed or presumptive events, or events requiring hospitalization. Among children <1 year of age we identified a significant 26% reduction in confirmed outpatient events and a non-significant 40% reduction in confirmed hospitalized events in the after PCV7
Acknowledgements
Funding support was provided through a Cooperative Agreement between the Center for Disease Control and Prevention (CDC) and the Association of Teachers of Preventive Medicine (ATPM), award number U50 CCU300860 TS-1244. We also thank Troy Scott and Shanshan Zhao for their programming and statistical analysis contributions.
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Impact of 7-valent versus 10-valent pneumococcal conjugate vaccines on primary care consultations across various age groups in the Netherlands, 5 years after the switch: A time-series analysis
2022, VaccineCitation Excerpt :Alternative proxies for non-IPD are therefore often used such as all-cause OM or pneumonia incidence. Studies in Europe and USA have demonstrated reductions in all-cause OM and pneumonia in children younger than 2 years following PCV7 introduction [21–27]. For older children and adults, impact of PCV7 on non-IPD is less convincing.
- 1
Control and Prevention, Atlanta GA, United States.
- 2
Children's Hospital and Regional Medical Center, Seattle WA, Unitedtates.