Modelling BCG vaccination in the UK

: What is the impact of changing policy?

Abstract

Bacillus Calmette–Guérin (BCG) remains the only licensed vaccine against Tubercu- losis (TB). In 2005, England changed from universal vaccination of school-age children to targeted vaccination of high-risk neonates. Little work has been done to assess the impact of this policy change. This thesis evaluates the impact of this change.

Whilst the characteristics of TB in England have been reported elsewhere, little at- tention has been given to the role of BCG. Consequently, I explored and combined, the available data sources. Reporting on data quality issues, trends in incidence rates and differences in outcomes stratified by BCG status.
Prior to the change in policy, several studies were carried out to assess the impact. I recreated one such study, correcting a methodological flaw, and found that there was a greater impact than previously thought.

Determining the benefits of being BCG vaccinated is necessary to properly assess the impact of the policy change. I evaluated the evidence that vaccination may improve outcomes for TB cases in England and found that there was some evidence of an association between vaccination and reduced mortality.

Surveillance data can help assess whether changes in vaccination policy have influ- enced incidence rates. I used surveillance data to determine whether those at school- age, or neonates, were affected by the policy change. I found that the policy change was associated with increased notifications in the UK born but this was outweighed by a reduction in notifications in the non-UK born.

Statistical modelling is restricted by the available data. Therefore, I developed a dynamic model of TB, fit to available data, to forecast the impact of the policy change. Although the fit to the data was poor, the forecasts suggested that continuing school-age vaccination reduced TB incidence in the UK born compared with neonatal vaccination. Neonatal vaccination reduced incidence in children but had little impact on other age groups.

Date of Award	28 Nov 2019
Original language	English
Awarding Institution	University of Bristol
Supervisor	Ellen Brooks Pollock (Supervisor) & Hannah Christensen (Supervisor)