Estimation of distribution of childhood diarrhoea, measles, and pneumonia morbidity and mortality by socio-economic group in low-income and middle-income countries
Background Vaccines are one of the most successful interventions in improving population health in low-income and
middle-income countries (LMICs). In addition to the direct improvements in health outcomes, we are interested
in their distributional effects—that is, whether vaccines promote or reduce health equity across socioeconomic
groups. Empirical data on incidence and mortality of vaccine-preventable diseases across socioeconomic groups
is not available. Therefore, we developed a method to estimate the distribution of childhood diseases and deaths
across income groups and the benefits of three vaccines—for diarrhoea, measles, and pneumonia—in 41 LMICs.
Methods For every country and disease (diarrhoea, measles, pneumonia), we estimated the distribution of cases and
deaths that would occur in each income quintile had there been no immunisation or treatment programme, using
both the prevalence and relative risk of a set of risk and prognostic factors. Building on these baseline estimates, we
assessed the effect of three vaccines (first dose of measles vaccine, pneumococcal conjugate vaccine, and rotavirus
vaccine) under five scenarios based on sets of quintile-specific immunisation coverage and uptake of disease
treatment.
Findings Because the prevalence of risk factors is higher in the poorest two quintiles than in the rest of the population,
more disease cases and deaths would occur in the poorest two quintiles for all three diseases when vaccines or treatment
are unavailable. However, we noted that current immunisation coverage and treatment utilisation rates have resulted in
greater inequity in the distribution of cases and deaths. Even if in absolute terms the poorest quintiles benefit more
from vaccines, the wealthier two quintiles sees a higher percentage decrease in cases and deaths. Thus, in terms of
overall distribution of remaining cases and deaths with vaccine coverage, the poorest quintiles would see a higher
comparative burden of disease than they would without vaccine coverage. Country-specific context, including how the
baseline risks, immunisation coverage, and treatment utilisation are currently distributed across quintiles, affects how
different policies translate to improvements in the distribution of cases and deaths.
Interpretation Our analysis highlights several factors, including risk and prognostic factors, and vaccine and treatment
coverage that would substantially contribute to the unequal distribution of childhood diseases, and we found that
merely ensuring equal access to vaccines will not reduce the health outcomes gap between income quintiles. Such
information can inform policies and planning of programmes that aim to improve equitable delivery of healthcare
services