Data from the Matlab cohort study<sup>by Koenia, et al. (1990)</sup> lead to similar conclusions.<sup>Among the cohort of children</sup> vaccinated at c12 months of<sup>age and their matched controls, if</sup> replacement mortality were present,<sup>one would expectto</sup> see higher mortality among vaccinated<sup>children with increasing time</sup> from vaccination, leading to<sup>a partial or complete convergence in</sup> survival curves for the two<sup>groups. The results instead indicate</sup> that vaccinated children continue<sup>to experience relatively lower</sup> mortality at almost all subsequent<sup>age intervals. Moreover, the</sup> magnitude of reductioi.s in<sup>mortality from measles vaccination</sup> reported in thes two studies<sup>(between 36 and 46 percent) suggest</sup> that even if such an effect<sup>were present, its impact upon</sup> lessening the mortality gains<sup>resulting from measles v,=cination</sup> would be quite minor. The<sup>studies from Matlab thus provide no</sup> support for the existence<sup>of a replacement mortality effect.</sup>

# Impact Among High-Risk Children

If replacement mortality were<sup>present, it should also be</sup> expected that the most vulnerable<sup>children would benefit least</sup> from measles immunization,<sup>since it is these children who</sup> continue to remain most at risk<sup>of death from other unaddressed</sup> causes. Within the context of<sup>South Asia, high risk children</sup> would include females and those<sup>from the poorest households, both</sup> of which have been shown to experience<sup>significantly higher</sup> mortality risks during the early<sup>childhood period (D'Souza and</sup> Chen, 1980; D'Souza and Bhuiva,<sup>1982). Data from the Matlab</sup> cohort study on measles immunization<sup>permit a more detailed</sup> investigation of this hypothesis.

Figure 3 shows life table results<sup>of the aifferential impact</sup> of measles vaccination upon mortality<sup>according to sex of child.</sup> If replacement mortality was present,<sup>little difference in the</sup> survival curves of female children<sup>according to vaccination</sup> status would be expected, since<sup>thev would continue to be at high</sup> risk of death from other causes.<sup>The results of this figure do</sup> not provide support for the replacement<sup>mortality hypothesis, and</sup> in fact, indicate the opposite--<sup>that female children may benefit</sup> more from vaccination in terms of<sup>mortality reductions.</sup> Vaccinating a female child against<sup>measles provides her with</sup> roughly the same survival chances<sup>as an unvaccinated male child.</sup> These result, are illustrated in<sup>greater detail in Figure 4.</sup> Although the relative reductions<sup>in mortality are not</sup> significantly different for male<sup>and female children (36 percent</sup> and 41 percent, respectively),<sup>because of the much higher</sup> mortality levels among female<sup>children during this age period,</sup> the absolute reduction in mortality<sup>for female children is more</sup> than twice that for male children<sup>(37 deaths vs. 17 deaths per,</sup> 1000 live births at 42 months post-vaccination).

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