Abstract
Incomplete immunisation coverage causes preventable illness and death in both developing and developed countries. Identification of factors that might modulate coverage could inform effective immunisation programmes and policies. We constructed a performance indicator that could quantitatively approximate measures of the susceptibility of immunisation programmes to coverage losses, with an aim to identify correlations between trends in vaccine coverage and socioeconomic factors. We undertook a data-driven time-series analysis to examine trends in coverage of diphtheria, tetanus, and pertussis (DTP) vaccination across 190 countries over the past 30 years. We grouped countries into six world regions according to WHO classifications. We used Gaussian process regression to forecast future coverage rates and provide a vaccine performance index: a summary measure of the strength of immunisation coverage in a country. Overall vaccine coverage increased in all six world regions between 1980 and 2010, with variation in volatility and trends. Our vaccine performance index identified that 53 countries had more than a 50% chance of missing the Global Vaccine Action Plan (GVAP) target of 90% worldwide coverage with three doses of DTP (DTP3) by 2015. These countries were mostly in sub-Saharan Africa and south Asia, but Austria and Ukraine also featured. Factors associated with DTP3 immunisation coverage varied by world region: personal income (Spearman's ρ=0·66, p=0·0011) and government health spending (0·66, p<0·0001) were informative of immunisation coverage in the Eastern Mediterranean between 1980 and 2010, whereas primary school completion was informative of coverage in Africa (0·56, p<0·0001) over the same period. The proportion of births attended by skilled health staff correlated significantly with immunisation coverage across many world regions. Our vaccine performance index highlighted countries at risk of failing to achieve the GVAP target of 90% coverage by 2015, and could aid policy makers' assessments of the strength and resilience of immunisation programmes. Weakening correlations with socioeconomic factors show a need to tackle vaccine confidence, whereas strengthening correlations point to clear factors to address. UK Engineering and Physical Sciences Research Council.
Highlights
Rates of vaccine-preventable diseases have decreased in many parts of the world in the past few decades, but many children remain unvaccinated
In 2013, UNICEF reported that 21·8 million children younger than 1 year had not completed the diphtheria, tetanus, and pertussis (DTP) immunisation series, with a similar number not receiving a single measles vaccination.[1]
Added value of this study We studied correlations between 190 socioeconomic factors and immunisation coverage in 190 countries, and report variations in the strength of socioeconomic correlates between world regions and across time
Summary
Rates of vaccine-preventable diseases have decreased in many parts of the world in the past few decades, but many children remain unvaccinated. In 2013, UNICEF reported that 21·8 million children younger than 1 year had not completed the diphtheria, tetanus, and pertussis (DTP) immunisation series, with a similar number not receiving a single measles vaccination.[1] access to vaccinations is the main barrier in many settings, growing numbers of parents do not immunise their children based on their own personal attitudes.[2,3]. Both socioeconomic and attitudinal barriers to vaccination coverage have been identified in several countries. Repeating themes have likewise been identified in examination of personal reasons for vaccine acceptance or delay, which range from perceived risks about potential adverse events, to religious or political beliefs that are external to, albeit influential in, vaccination.[9,19,20,21,22,23,24,25,26,27] Trust in health-care professionals[19,20,23,24] and the government[19,23,26] features highly
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