Invasive Pneumococcal Disease a Decade after Pneumococcal Conjugate Vaccine Use in an American Indian Population at High Risk for Disease

Abstract

Background. Before 7-valent pneumococcal conjugate vaccine (PCV7) introduction, invasive pneumococcal disease (IPD) rates among Navajo were several-fold those of the general US population. Only 50% of IPD cases in children involved PCV7 serotypes.Methods. We conducted active, population-based surveillance for IPD for the period 1995-2006. We documented case characteristics and serotyped the isolates. Results. Over 12-year period, we identified 1508 IPD cases, 447 of which occurred in children aged !5 years. Rates of IPD due to vaccine serotypes among children aged !1 year, 1 to !2 years, and 2 to !5 years decreased from 210, 263, and 51 cases per 100,000 population, respectively in 1995-1997 to 0 cases in 2004-2006 (P ! .001). Among adults aged у65 years, rates of IPD due to vaccine serotypes decreased 81% (95% confidence interval, Ϫ98% to Ϫ9%; P p .02). Rates of nonvaccine serotype IPD were unchanged in all age strata except for persons aged 18 to !40 years, among whom the rate decreased by 35% from 27 to 18 cases per 100,000 population (95% confidence interval, Ϫ57% to Ϫ1%; P p .03).Conclusions. Vaccine-serotype IPD has virtually been eliminated in the PCV7 era among Navajo of all ages. Overall rates of nonvaccine-serotype IPD have not increased, although increases have occurred for some individual types. Rates of all-serotype IPD among Navajo children remain 3-5-fold greater than in the general US population.

Serotype 3 is a common serotype causing invasive pneumococcal disease in children less than 5 years old, as identified by real-time PCR

“…The serotype distribution of patients identified by culture reported in this study is similar to what other authors have found [17,18]. The most prevalent serotype in patients identified by culture is serotype 1, as in other regions of Spain and in Portugal.…”

Pre– and Post–Conjugate Vaccine Epidemiology of Pneumococcal Serotype 6C Invasive Disease and Carriage within Navajo and White Mountain Apache Communities

“…In the United States, these rate increases are small relative to the major decreases in vaccine serotype disease that have been achieved. Among certain Native American populations with high underlying rates of pneumococcal disease, the magnitude of the nonvaccine serotype replacement disease has ranged from small among Navajo and White Mountain Apache populations [5,6] to large among Alaska Natives [4]. The broad diversity of pneumococcal serotypes capable of causing disease has fueled development of second-generation pneumococcal conjugate vaccines with increased valency (ie, broader serotype coverage).…”

“…The issues of novel serotype emergence and effectiveness of new PCVs are particularly important for some Native American communities, where disproportionately high rates of pneumococcal disease and carriage have persisted in spite of high levels of immunization coverage [4][5][6]. Over the past 12 years, we have conducted a number of population-based studies of pneumococci and established a repository of isolates, collected in the context of a large-scale, cluster-randomized vaccine efficacy trial [13], ongoing laboratory-based active surveillance for invasive disease [6], and a number of household-based studies of nasopharyngeal carriage [14][15][16].…”

Lessons Learnt after the Introduction of the Seven Valent‑Pneumococcal Conjugate Vaccine Toward Broader Spectrum Conjugate Vaccines

“…[18] In the Navajo population, between 1995 and 2006, in an active surveillance system which included 1508 cases of IPD the total number of cases decreased from 67 in 1995-1997 to 51 cases in the years following PCV7 introduction. [20] There was no change in the nonvaccine type (NVT) in children in the post vaccine era. Rates increased for serotypes 1, 3, 5, 7F, 19A, 18B.…”

“…In infants under the age of 2 months no cases with serotype included in the PCV7 was reported with no replacement by NVT disease. [20] A combined study of four European countries was done after PCV7 introduction in Europe. [21] Different countries have implemented vaccination in various time periods, but all consider the 7 serotypes contained in the vaccine as being responsible for 68% to 77% of IPD in children under 5 years of age.…”