BCG vaccination in England since 2005: a survey of policy and practice

Reassessing the evidence for universal school-age BCG vaccination in England and Wales: re-evaluating and updating a modelling study

OBJECTIVES

In 2005, England and Wales switched from universal BCG vaccination against tuberculosis (TB) disease for school-age children to targeted vaccination of neonates. We aimed to recreate and re-evaluate a previously published model, the results of which informed this policy change.

DESIGN

We recreated an approach for estimating the impact of ending the BCG schools scheme, correcting a methodological flaw in the model, updating the model with parameter uncertainty and improving parameter estimates where possible. We investigated scenarios for the assumed annual decrease in TB incidence rates considered by the UK's Joint Committee on Vaccination and Immunisation and explored alternative scenarios using notification data.

SETTING

England and Wales.

OUTCOME MEASURES

The number of vaccines needed to prevent a single notification and the average annual additional notifications caused by ending the policy change.

RESULTS

The previously published model was found to contain a methodological flaw and to be spuriously precise. It greatly underestimated the impact of ending school-age vaccination compared with our updated, corrected model. The updated model produced predictions with wide CIs when parameter uncertainty was included. Model estimates based on an assumption of an annual decrease in TB incidence rates of 1.9% were closest to those estimated using notification data. Using this assumption, we estimate that 1600 (2.5; 97.5% quantiles: 1300, 2000) vaccines would have been required to prevent a single notification in 2004.

CONCLUSIONS

The impact of ending the BCG schools scheme was found to be greater than previously thought when notification data were used. Our results highlight the importance of independent evaluations of modelling evidence, including uncertainty, and evaluating multiple scenarios when forecasting the impact of changes in vaccination policy.

The Changing Landscape of Childhood Tuberculosis in the United Kingdom: A Retrospective Cohort (2000-2015)

BACKGROUND

The epidemiology of tuberculosis (TB) is changing in the United Kingdom and globally. Childhood TB is a key indicator of recent transmission and provides a marker of wider TB control. We describe the recent epidemiology of childhood TB in the United Kingdom, how this compares to TB in adults, and document changes with time.

METHODS

TB cases notified in the United Kingdom between 2000 and 2015 were categorized as children (<15 years of age) or adults (≥15 years of age). Descriptive analyses were carried out on demographic, clinical and microbiologic data. We carried out logistic regressions to identify risk factors associated with children having no microbiologic confirmation.

RESULTS

In the study period, 6293 TB cases (5%) in the United Kingdom were notified in children. Childhood TB incidence declined from 487 cases in 2000 (3.4 per 100,000) to 232 cases (2.0 per 100,000) in 2015. The majority (68%) of children with TB were UK born, with a high proportion of Pakistani (24%) and Black-African (22%) ethnicity. Sixty-four percent of children had pulmonary disease. Culture confirmation was low (24%). Children who were younger, UK born and those with extrapulmonary disease were less likely to have microbiologically confirmed TB. A high proportion (87%) of children completed treatment at last-recorded outcome, with few deaths (39 cases; 0.7%).

CONCLUSIONS

The incidence of TB in children in the United Kingdom has decreased in the past 16 years, with the majority of children completing TB treatment. Ongoing monitoring of childhood TB will provide a measure of the effectiveness of the national TB program.

Observational study to estimate the changes in the effectiveness of bacillus Calmette-Guérin (BCG) vaccination with time since vaccination for preventing tuberculosis in the UK

BACKGROUND

Until recently, evidence that protection from the bacillus Calmette-Guérin (BCG) vaccination lasted beyond 10 years was limited. In the past few years, studies in Brazil and the USA (in Native Americans) have suggested that protection from BCG vaccination against tuberculosis (TB) in childhood can last for several decades. The UK's universal school-age BCG vaccination programme was stopped in 2005 and the programme of selective vaccination of high-risk (usually ethnic minority) infants was enhanced.

OBJECTIVES

To assess the duration of protection of infant and school-age BCG vaccination against TB in the UK.

METHODS

Two case-control studies of the duration of protection of BCG vaccination were conducted, the first on minority ethnic groups who were eligible for infant BCG vaccination 0-19 years earlier and the second on white subjects eligible for school-age BCG vaccination 10-29 years earlier. TB cases were selected from notifications to the UK national Enhanced Tuberculosis Surveillance system from 2003 to 2012. Population-based control subjects, frequency matched for age, were recruited. BCG vaccination status was established from BCG records, scar reading and BCG history. Information on potential confounders was collected using computer-assisted interviews. Vaccine effectiveness was estimated as a function of time since vaccination, using a case-cohort analysis based on Cox regression.

RESULTS

In the infant BCG study, vaccination status was determined using vaccination records as recall was poor and concordance between records and scar reading was limited. A protective effect was seen up to 10 years following infant vaccination [< 5 years since vaccination: vaccine effectiveness (VE) 66%, 95% confidence interval (CI) 17% to 86%; 5-10 years since vaccination: VE 75%, 95% CI 43% to 89%], but there was weak evidence of an effect 10-15 years after vaccination (VE 36%, 95% CI negative to 77%; p = 0.396). The analyses of the protective effect of infant BCG vaccination were adjusted for confounders, including birth cohort and ethnicity. For school-aged BCG vaccination, VE was 51% (95% CI 21% to 69%) 10-15 years after vaccination and 57% (95% CI 33% to 72%) 15-20 years after vaccination, beyond which time protection appeared to wane. Ascertainment of vaccination status was based on self-reported history and scar reading.

LIMITATIONS

The difficulty in examining vaccination sites in older women in the high-risk minority ethnic study population and the sparsity of vaccine record data in the later time periods precluded robust assessment of protection from infant BCG vaccination > 10 years after vaccination.

CONCLUSIONS

Infant BCG vaccination in a population at high risk for TB was shown to provide protection for at least 10 years, whereas in the white population school-age vaccination was shown to provide protection for at least 20 years. This evidence may inform TB vaccination programmes (e.g. the timing of administration of improved TB vaccines, if they become available) and cost-effectiveness studies. Methods to deal with missing record data in the infant study could be explored, including the use of scar reading.

FUNDING

The National Institute for Health Research Health Technology Assessment programme. During the conduct of the study, Jonathan Sterne, Ibrahim Abubakar and Laura C Rodrigues received other funding from NIHR; Ibrahim Abubakar and Laura C Rodrigues have also received funding from the Medical Research Council. Punam Mangtani received funding from the Biotechnology and Biological Sciences Research Council.