Abstract
BackgroundIn 2008, a 7-valent pneumococcal conjugate vaccine (PCV7) was introduced into the routine childhood immunization program in Uruguay, with a 2+1 schedule. In 2010, PCV13 replaced PCV7, and the same 2+1 schedule was used. The effect of these pneumococcal vaccines on the incidence of invasive pneumococcal infections (IPD) and on serotype distribution was analyzed retrospectively, based on passive national laboratory surveillance.MethodsData from 1,887 IPD isolates from 5 years before and 5 years after PCV7 introduction (7 before and 3 after PCV13 introduction) was examined to assess the incidence rate per 100,000 age-specific population of all IPD, PCV7-serotypes, and PCV13-serotypes associated IPD among children <2 years and 2 to 4 years old, and patients ≥5 years old. Trends of frequency for each serotype were also analyzed.ResultsComparison of pre-vaccination (2003–2007) and post-vaccination (2008–2012) periods showed a significant decrease in IPD incidence among children <2 years old (IR 68.7 to IR 29.6, p<0.001) and children 2 to 4 years (p<0.04). IPD caused by serotypes in PCV7 was reduced by 95.6% and IPD caused by 6 serotypes added in PCV13 was reduced by 83.9% in children <5 years old. Indirect effects of both conjugate vaccines were observed among patients ≥5 years old one year after the introduction of each vaccine, in 2010 for PCV7 and in 2012 for PCV13. Nevertheless, for reasons that still need to be explained, perhaps due to ascertainment bias, total IPD in this group increased after 2007. In 2012, the relative frequency of vaccine serotypes among vaccinated and unvaccinated population declined, except for serotype 3. Non vaccine serotypes with increasing frequency were identified, in rank order: 12F, 8, 24F, 22F, 24A, 15C, 9N, 10A and 33.ConclusionConsecutive immunization with PCV7 and PCV13 has significantly reduced IPD in children <5 years of age in Uruguay.
Highlights
Invasive pneumococcal disease (IPD) is still a major cause of morbidity and mortality in children under 5 years old, the elderly and immunocompromised patients
For incidence rates (IR) calculation, the last group was further subdivided into 3 groups: 5–14 years old (n = 207), 15–59 years old (n = 499) and $60 years old (n = 439)
A significant reduction of IR between pre- (2003–2007) and post- (2008–2012) vaccination period, was observed in this group of age, from 68.7 to 23.25 for total IPD cases (Table 2). Differences between both periods were significant for the same age group when VT-PCV7 and for VT-PCV13 associated IPD was analyzed
Summary
Invasive pneumococcal disease (IPD) is still a major cause of morbidity and mortality in children under 5 years old, the elderly and immunocompromised patients. A seven-valent pneumococcal conjugate vaccine (PCV7), first introduced in the United States in 2000, has been remarkably effective in reducing IPD caused by pneumococci of serotypes included in the formula (4, 6B, 9V, 14, 18C, 19F and 23F) among vaccinated children. While VT-PCV7 virtually disappeared as a cause of IPD in countries with .3 years vaccination, serotype replacement and emergence of ‘‘new’’ serotypes have been observed, first as an increase in carriage and later as an increase in invasive disease [2,3]. In 2010, PCV13 replaced PCV7, and the same 2+1 schedule was used The effect of these pneumococcal vaccines on the incidence of invasive pneumococcal infections (IPD) and on serotype distribution was analyzed retrospectively, based on passive national laboratory surveillance
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