Elsevier

Mayo Clinic Proceedings

Volume 84, Issue 10, October 2009, Pages 871-875
Mayo Clinic Proceedings

ORIGINAL ARTICLE
Incidence of Invasive Pneumococcal Disease Among Children After Introduction of a 7-Valent Pneumococcal Conjugate Vaccine: A Population-Based Study in Olmsted County, Minnesota

https://doi.org/10.4065/84.10.871Get rights and content

OBJECTIVE

To examine the effect of the 7-valent pneumococcal conjugate vaccine in a well-characterized population in Olmsted County, Minnesota, with a combination of urban and rural residents likely to have a relatively low risk of invasive pneumococcal disease (IPD).

PATIENTS AND METHODS

This population-based study analyzed data from children younger than 5 years to determine the incidence of IPD from January 1, 1995, to December 31, 2007.

RESULTS

From 1995 through 2007, 29 cases of IPD were identified in the study population, but 2 patients denied research authorization; thus, 27 cases were available for review. From 1995-1999 to 2001-2003, the incidence of IPD decreased from 33.5 (95% confidence interval [CI], 16.6-50.5) to 10.8 (95% CI, 0.0-23.0) cases per 100,000 person-years (68% decrease; P=.046). The incidence subsequently increased to 15.2 (95% CI, 3.0-27.4) cases per 100,000 person-years from 2004 through 2007; however this change was not significant (P=.62). All cases of IPD with available serotype data from 2002 through 2007 (n=5) were due to non-7-valent conjugate vaccine serotypes.

CONCLUSION

Although the baseline incidence of IPD was much lower than that reported in other populations, the overall incidence of IPD decreased significantly in children younger than 5 years after introduction of a 7-valent conjugate vaccine.

Section snippets

Population

Olmsted County (total population, 124,277; population <5 years, 8890; 2000 census data) is located in southeastern Minnesota and includes the central city of Rochester (total population, 85,806; population <5 years, 6401; 2000 census data) and the surrounding area. Most of the population is white (90.3% white; 2000 census data) and of Northern European ancestry. One unique feature of the Olmsted County population is that medical care is mainly self-contained within the community.8 This is due

RESULTS

Twenty-nine cases of IPD were identified in children younger than 5 years. For 2 children with IPD, research authorization was refused, and their records were not used for research purposes in accordance with the Minnesota Research Authorization Statute. Therefore, 27 (93%) of the 29 IPD cases were available for review.

DISCUSSION

In the population of Olmsted County, where the pre-PCV-7 incidence of IPD in children younger than 5 years (33.5 cases per 100,000 person-years) was much lower than the pre-PCV-7 incidence of IPD in other populations (ranging from 62.5 to 473 cases per 100,000 person-years),1, 2, 5, 7 we observed a similar substantial decrease (68%) in the incidence of IPD after introduction of PCV-7. The decrease in IPD incidence in children in Olmsted County was likely related to the introduction of PCV-7 in

CONCLUSION

A significant decrease was noted in the incidence of IPD in children younger than 5 years in Olmsted County, Minnesota, after the introduction of PCV-7 in 2000. Further surveillance is needed in the upcoming years to monitor for increasing IPD incidence in young children.

Acknowledgments

We thank Mary Ann Butler at the Olmsted Medical Center Hospital laboratory for assistance in obtaining microbiology data and Barbara Yawn, MD, at the Olmsted Medical Center for her assistance with vaccination data. Neither received compensation for her work on this study.

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This work was made possible by grant R01 AR30582 (Rochester Epidemiology Project) from the National Institutes of Health (NIH) and the National Institute of Arthritis and Musculoskeletal and Skin Diseases, by grant UL1 RR024150 from the National Center for Research Resources (NCRR), a component of the NIH, and the NIH Roadmap for Medical Research, and in part by intramural research funding by the Small Grants Program and the Baddour Family Fund Research Grants Program from Mayo Clinic's site in Rochester, MN.

Its contents are solely the responsibility of the authors and do not necessarily represent the official view of NCRR or NIH. Information on NCRR is available at http://www.ncrr.nih.gov/. Information on Reengineering the Clinical Research Enterprise can be obtained from http://nihroadmap.nih.gov.

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