Hesitancy in vaccination programmes has increased over the past few decades and has led to vaccination delays and refusals resulting in epidemic outbreaks and curtailing progress towards disease elimination. Addressing vaccine hesi- tancy is a public health priority. In this thesis we assess the global state of vaccine coverage and vaccine hesitancy by performing a number of timely anal- yses, providing key public health messages. These analyses can be used to address vaccine coverage and inform effective immunisation programmes and policies.
In Chapter 2, we assess national-level childhood immunisation programmes by forecasting each nation’s vaccine coverage rates. By these means we are able to provide estimates of likely future coverage levels and derive a quantitative measure of the strength of a country’s immunisation programme – a measure we term the vaccine performance index. In countries where vaccines are freely available, our index captures losses to coverage based on hesitancy issues (non- access barriers that centre on personal beliefs and attitudes such as confidence in vaccines). We perform the first global-scale quantitative analysis of time- varying socio-economic determinants of vaccine coverage.
In Chapter 3, we focus on direct measures of attitudes to vaccines. Using the largest survey ever conducted on attitudes to vaccines (almost 70,000 individ- uals across 67 countries), we examine global variation in (and socio-economic determinants of) attitudes to vaccines. This is achieved through a four-question survey on individuals’ perceptions of vaccine safety, importance, effectiveness, and religious compatibility. In Chapter 4, we use a latent variable method to project these four attitudinal dimensions onto a single dimension which we claim to be the first quantitative measure of individual’s vaccine hesitancy. This measure is termed the vaccine hesitancy index and we infer hesitancy for each individual. Hesitancy is investigated globally and we perform a case study of hesitancy in Nigeria, where there have been notable recent concerns with vac- cinations.
Identifying countries with sub-optimal immunisation rates, vaccine-hesitant groups, and understanding socio-economic correlates of coverage and hesitancy enables
us to understand the complex coverage-hesitancy interplay and address gaps in coverage.