Changing epidemiology of invasive pneumococcal disease among White Mountain Apache persons in the era of the pneumococcal conjugate vaccine.

Center for American Indian Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA.
Clinical Infectious Diseases (Impact Factor: 9.37). 08/2008; 47(4):476-84. DOI: 10.1086/590001
Source: PubMed

ABSTRACT Prior to the introduction of the 7-valent pneumococcal conjugate vaccine (PCV7), the rate of invasive pneumococcal disease (IPD) was 8-fold higher among White Mountain Apache persons of all ages than it was among the general US population, . We aimed to assess the impact of PCV7 and 23-valent pneumococcal polysaccharide vaccine on the rate of IPD among White Mountain Apache persons.
From 1991 through 2006, we conducted active laboratory- and population-based surveillance among Native American residents of the White Mountain Apache reservation. Charts were reviewed and pneumococcal isolates were collected for serotype testing. Three time periods were defined: the pre-PCV7 baseline period (1991-1997), the PCV7 efficacy trial period (1998-2000), and the PCV7 routine-use period (2001-2006).
We identified 246 cases of IPD; the mean annual IPD rate fell from 126 cases per 100,000 person-years in the period 1991-1997 to 87 cases per 100,000 person-years in the period 2001-2006 (p = .01). The rate of IPD attributable to PCV7 serotypes of Streptococcus pneumoniae decreased by 252 cases per 100,000 person-years (92%) among children aged <5 years, and that attributable to non-PCV7 serotypes of S. pneumoniae decreased by 87 cases per 100,000 person-years (44%) among children aged <5 years. Among adults, the rate of IPD remained unchanged; PCV7 serotypes of S. pneumoniae accounted for only 25% of adult cases during the period 1991-1997.
Since the introduction of PCV7, the rate of IPD among White Mountain Apache children aged <5 years has decreased to the lowest rate ever (122 cases per 100,000 person-years), but it remains 5.7-fold greater than the rate of IPD among children in the general US population. In contrast to some other high-risk populations, there is no evidence of non-vaccine-type replacement disease in this age group. Among White Mountain Apache adults, the rate of IPD remains substantially higher than that observed in the general US population. Vaccines with broader serotype coverage are needed to further reduce the disparity in the rate of IPD between the White Mountain Apache and general US populations.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Characterisation of risk groups who may benefit from pneumococcal vaccination is essential for the generation of recommendations and policy. We reviewed the literature to provide information on the incidence and risk of invasive pneumococcal disease (IPD) in at-risk children in Europe and North America. The PubMed database was searched using predefined search terms and inclusion/exclusion criteria for papers reporting European or North American data on the incidence or risk of IPD in children with underlying medical conditions. Eighteen references were identified, 11 from North America and 7 from Europe, with heterogeneous study methods, periods and populations. The highest incidence was seen in US children positive for human immunodeficiency virus infection, peaking at 4167 per 100,000 patient-years in 2000. Studies investigating changes in incidence over time reported decreases in the incidence of IPD between the late 1990s and early 2000s. The highest risk of IPD was observed in children with haematological cancers or immunosuppression. Overall, data on IPD in at-risk children were limited, lacking incidence data for a wide range of predisposing conditions. There was, however, a clear decrease in the incidence of IPD in at-risk children after the introduction of 7-valent pneumococcal conjugate vaccine into immunisation programmes, as previously demonstrated in the general population. Despite the heterogeneity of the studies identified, the available data show a substantial incidence of IPD in at-risk children, particularly those who are immunocompromised. Further research is needed to determine the true risk of IPD in at-risk children, particularly in the post-PCV period, and to understand the benefits of vaccination and optimal vaccination schedules.
    International Journal of Clinical Practice 07/2013; · 2.43 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A second-generation 13-valent pneumococcal conjugate vaccine, PCV13, was recently licensed. Although PCV13 includes serotype 6A, the usefulness of that antigen may be limited by the emergence of a new serotype, 6C, which was identified among isolates initially characterized (Quellung reaction) as serotype 6A. The epidemiology of serotype 6C prior to and after 7-valent PCV (PCV7) introduction is incompletely understood. We analyzed conventionally serotyped 6A (CS6A) pneumococci from invasive disease case patients of all ages and carriage isolates from children and adults obtained in population-based studies among Navajo and White Mountain Apache communities during 1994-2009. Samples were tested by triplex polymerase chain reaction to resolve serotypes 6C and 6A. A total of 74 invasive CS6A episodes occurred. All were retyped by polymerase chain reaction; 40 (54.1%) were serotype 6C. The mean annual incidence of serotype 6C invasive disease was 0.3 (95% confidence interval, 0.03-0.9), 0.7 (95% confidence interval, 0.2-1.3), and 1.5 (95% confidence interval, 1.0-2.1) cases per 100,000 population in the years prior to the PCV7 efficacy trial, during the time the PCV7 trial was conducted, and following PCV7 introduction and routine use, respectively (P = .01). In the routine vaccination era, 76% of invasive CS6As were serotype 6C; nearly all cases occurred in adults. The proportion of serotype 6C among CS6A carriage isolates increased from 42% to 61% to 94% in the prevaccine, early vaccine, and routine vaccination eras, respectively. In the PCV7 routine use era, virtually all serogroup 6 invasive pneumococcal disease and carriage strains among Navajo and White Mountain Apache communities are 6C. Monitoring and evaluation of this and other emerging serotypes among invasive disease and carriage isolates is warranted.
    Clinical Infectious Diseases 10/2010; 51(11):1258-65. · 9.37 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Since second generation pneumococcal conjugate vaccines (PCVs) targeting 10 and 13 serotypes became available in 2010, the number of national policy makers considering these vaccines has steadily increased. An important consideration for a national immunization program is the timing and number of doses-the schedule-that will best prevent disease in the population. Data on disease epidemiology and the efficacy or effectiveness of PCV schedules are typically considered when choosing a schedule. Practical concerns, such as the existing vaccine schedule, and vaccine program performance are also important. In low-income countries, pneumococcal disease and deaths typically peak well before the end of the first year of life, making a schedule that provides PCV doses early in life (eg, a 6-, 10- and 14-week schedule) potentially the best option. In other settings, a schedule including a booster dose may address disease that peaks in the second year of life or may be seen to enhance a schedule already in place. A large and growing body of evidence from immunogenicity studies, as well as clinical trials and observational studies of carriage, pneumonia and invasive disease, has been systematically reviewed; these data indicate that schedules of 3 or 4 doses all work well, and that the differences between these regimens are subtle, especially in a mature program in which coverage is high and indirect (herd) effects help enhance protection provided directly by a vaccine schedule. The recent World Health Organization policy statement on PCVs endorsed a schedule of 3 primary doses without a booster or, as a new alternative, 2 primary doses with a booster dose. While 1 schedule may be preferred in a particular setting based on local epidemiology or practical considerations, achieving high coverage with 3 doses is likely more important than the specific timing of doses.
    The Pediatric Infectious Disease Journal 01/2014; 33 Suppl 2:S172-81. · 3.57 Impact Factor