IJE Advance Access originally published online on November 23, 2004
International Journal of Epidemiology 2005 34(1):138-148; doi:10.1093/ije/dyh262
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IJE vol.34 no.1 © International Epidemiological Association 2004; all rights reserved.
Article |
Benefits of routine immunizations on childhood survival in Tari, Southern Highlands Province, Papua New Guinea
1 Papua New Guinea Institute of Medical Research, Goroka and Tari, Papua New Guinea
2 Centre for Child Health Research, University of Western Australia, Telethon Institute for Child Health Research, Perth, Western Australia
3 Centre for International Health, Curtin University of Technology, Perth, Western Australia
* Corresponding author. Dr Deborah Lehmann, Telethon Institute for Child Health Research, PO Box 855, West Perth, WA 6872, Australia. E-mail: deborahl{at}ichr.uwa.edu.au
Background Non-specific beneficial as well as deleterious effects of childhood immunizations have been reported in areas of high mortality. This study aimed to determine the effects of diphtheria-tetanus-whole-cell-pertussis (DTP), BCG, hepatitis B, and measles vaccines on mortality in the highlands of Papua New Guinea (PNG).
Methods Demographic events for children born in 1989–1994 who were under monthly demographic surveillance in Tari were recorded from birth until age 2 years, out-migration, death, or the end of the study period. Data on BCG, hepatitis B, DTP, measles and pneumococcal polysaccharide vaccination were collected monthly from clinic records. To allow for different characteristics of immunized and non-immunized children, analysis included conditioning on a propensity score for vaccination, adjusting for differences in children's background characteristics.
Results In all, 101/3502 children (3%) who had at least one vaccine died between ages 29 days and 24 months were compared to 112/546 (21%) who had none. BCG was associated with lower mortality in the 1–5 month age group (hazard ratio [HR] = 0.17, 95% CI: 0.09, 0.34), measles vaccine with lower mortality at age 6–11 months (HR = 0.42, 95% CI: 0.17, 1.01), and pneumococcal polysaccharide vaccine with lower mortality at age 12–23 months (HR = 0.42, 95% CI: 0.19, 0.93). One or more doses of DTP was associated with lower overall mortality (HR = 0.27, 95% CI: 0.16, 0.44), particularly in the 1–5 month age group (HR = 0.19, 95% CI: 0.10, 0.34), and also in those who had had prior BCG (HR = 0.45, 95% CI: 0.22, 0.91).
Conclusion Routine immunizations are effective in reducing overall mortality in young children in an area of high mortality. In particular, DTP, whether considered separately or in addition to BCG, was associated with a lowering of overall mortality, in contrast to findings reported from Guinea-Bissau.
Keywords Childhood immunization, BCG, DTP vaccine, immunization programmes, measles vaccine, pneumococcal polysaccharide vaccine, mortality, Papua New Guinea, survival analysis, propensity score
Accepted 21 May 2004
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