Forecasting time-series trends in vaccination coverage and their links with socio-economic factors: A global analysis over 30 years

In: Lancet Global Health

Abstract

Background Incomplete immunisation coverage causes preventable illness and death in both the developing and developed world. Identifying factors that may modulate coverage can inform effective immunisation programmes and policies. Methods We perform a data-driven analysis of unprecedented scale, examining time-varying trends in Diphtheriatetanus-pertussis coverage across 190 countries over the past three decades. Gaussian process regression is employed to forecast future coverage rates and provide a Vaccine Performance Index: a summary measure of the strength of immunisation coverage in a country. Findings Overall vaccine coverage has increased in all five world regions between 1980 and 2010, with marked variation in volatility and trends. Our Vaccine Performance Index identifies 53 countries with a less than 50% chance of missing the Global Vaccine Action Plan (GVAP) target of 90% worldwide DTP3 coverage by 2015, in agreement with recent immunisation data. These countries are mostly sub-Saharan and South Asian, but Austria and Ukraine in Europe also feature. Factors associated with DTP3 immunisation coverage vary by world-region: personal income (! = 0.66, ' < 0.001) and government health spending (! = 0.66, ' < 0.01) are particularly informative in the Eastern Mediterranean between 1980 and 2010, whilst primary school completion is informative in Africa (! = 0.56, ' < 0.001) over the same time. The fraction of births attended by skilled health staff is significantly informative across many world regions Interpretation A Vaccine Performance Index can highlight countries at risk identifying the strength and resilience of immunisation programmes. Weakening correlations with socio-economic factors indicate a need to tackle vaccine confidence whereas strengthening correlations points to clear factors to address.