Trends in invasive pneumococcal disease among older adults in Olmsted County, Minnesota.
OBJECTIVE
Following the introduction of a 7-valent pneumococcal conjugate vaccine (PCV-7) for children in early 2000 in the United States, a decrease in the incidence of invasive pneumococcal disease (IPD) was seen in adults, likely due to a herd effect. However, there have been recent increases in IPD in adults caused by Streptococcus pneumoniae serotypes not included in PCV-7, so called "replacement disease". We performed a population-based study to further investigate this emerging concern.


METHODS
Population-based incidence study in Olmsted County, Minnesota, United States, in adults aged > or =50 years.


RESULTS
From 1/1/1995 to 12/31/2007, 104 cases of IPD were identified in Olmsted County in adults aged > or =50 years. We found a 45% increase in the incidence rate of IPD from 2001-2003 (17.7 cases per 100,000 person-years) to 2004-2007 (32.1 cases per 100,000 person-years) (p=0.029). From 2002-2004 to 2005-2007, the incidence rate of IPD caused by S. pneumoniae serotypes not included in PCV-7 increased from 9.2 to 32.8 cases per 100,000 person-years (p<0.001).


CONCLUSIONS
A recent increase in the incidence of IPD in adults aged > or =50 years was demonstrated in Olmsted County, Minnesota due to serotypes not found in PCV-7. These findings are unique and merit further investigation.
Tsigrelis
Constantine
C
Department of Medicine, Division of Infectious Diseases, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN, USA. tsigrelis.constantine@yahoo.com
Tleyjeh
Imad M
IM
Lahr
Brian D
BD
Nyre
Lisa M
LM
Virk
Abinash
A
Baddour
Larry M
LM
D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D008910:Minnesota / Q000453:epidemiology; D011008:Pneumococcal Infections / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology*; D022242:Pneumococcal Vaccines; D011018:Pneumonia, Pneumococcal / Q000453:epidemiology; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification
D022242:Pneumococcal Vaccines