Temporal trends in invasive pneumococcal disease and pneumococcal serotypes over 7 decades

Clin Infect Dis. 2010 Feb 1;50(3):329-37. doi: 10.1086/649872.


Background: Pneumococcal infections have historically played a major role in terms of morbidity and mortality. We explored historical trends of invasive pneumococcal disease (IPD) and pneumococcal serotypes in a population exposed to limited antibiotic selective pressure and conjugate pneumococcal vaccination (PCV).

Methods: Retrospective cohort study based on nationwide laboratory surveillance data on IPD collected uninterruptedly in Denmark during 1938-2007. Changes in the reported incidence and trends of pneumococcal serotypes were explored using nonlinear regression analysis.

Results: There were 25,502 IPD cases included in our study. The median incidence of IPD increased from 2.8 cases per 100,000 population (interquartile range [IQR], 1.5-2.6) during the first 4 decades to 15.7 cases per 100,000 population (IQR, 7-20.4) during the 1980s and 1990s, mainly attributed to an increase in the number of bacteremia cases. The incidence of meningitis remained relatively stable, with a median of 1.3 cases per 100,000 population (IQR, 0.9-1.6). The proportions of serotypes/groups 4 and 9 increased; the proportion of serotype 18C decreased; the proportions of serotypes 6, 7F, 14, and 23F remained stable; and serotype 2 nearly disappeared. Before the 1960s, serotypes 1, 2, 3, and 5 presented peaks every 2-3 years, becoming less frequent during the 1970s with peaks every 7-10 years. Between 20% and 90% of IPD in children <5 years were caused by PCV serotypes during the last 4 decades. Cases of IPD caused by serotype 19A increased before introduction of PCV. Between 1993 and 2007, the level of resistance to macrolides and beta-lactams was 6%.

Conclusions: The epidemiology of IPD and single serotypes has constantly changed over the past 7 decades. PCV serotypes appeared to dominate the pneumococcal population.

Publication types

  • Historical Article

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Child
  • Child, Preschool
  • Cohort Studies
  • Denmark / epidemiology
  • Female
  • History, 20th Century
  • History, 21st Century
  • Humans
  • Incidence
  • Infant
  • Infant, Newborn
  • Male
  • Middle Aged
  • Pneumococcal Infections / epidemiology*
  • Pneumococcal Infections / history
  • Pneumococcal Infections / microbiology*
  • Retrospective Studies
  • Serotyping
  • Streptococcus pneumoniae / classification*
  • Streptococcus pneumoniae / isolation & purification
  • Young Adult