Dr Rebecca Harris
Potential impact of new tuberculosis vaccines in China, South Africa and India and implications for vaccine development
Background: New tuberculosis vaccines are needed to help reach the WHO 2050 TB elimination goal. Insufficient evidence exists on the potential impact of new TB vaccines with varying characteristics and in different epidemiological settings. Two phase IIB trials reported positive efficacy results in 2018. To inform decision making, we estimated impact of new TB vaccines in three high-burden countries using mathematical models.
Methods: TB models were calibrated to age-stratified demographic and epidemiological data from China, South Africa and India. Vaccine efficacy to prevent infection and/or disease, effective in persons M.tb uninfected and/or infected, andduration of protectionwere varied. Routine earlyadolescent vaccination and 10-yearly mass campaigns were introduced from 2025. Median population-level TB incidence rate reduction in 2050 compared to a no-new-vaccine scenario (%IRR) was estimated.
Results: In all settings, results suggest that vaccines preventing disease in M.tb-infected populations would have most impact by 2050 (10-year, 70% efficacy against disease, IRR 51%, 51% and 54% in China, South Africa and India, respectively). Vaccines preventing re-infection delivered lower impact(IRR 1%, 6% and 17%). Intermediate impact was predicted for vaccines effective only in uninfected populations, if preventing only infection(IRR 21%, 32% and 50%), or disease(IRR 19%, 26%, 51%), with greater impact in higher transmission settings. Using phase IIB results, and assuming 10 years protection, predicted IRR for BCG revaccination 50% effective for preventing infection in uninfected populations was 16%, 19% and 39% for China, South Africa and India; and for M72/AS01E 50% effective for preventing disease in infected populations was 37%, 32% and 41%, respectively.
Conclusions: New TB vaccines could deliver substantial population-level impact. If prioritising impact by 2050, vaccine development should focus on preventing disease in M.tb-infected populations. Vaccines preventing infection or disease in uninfected populations may be useful in higher transmission settings. Impact depended upon epidemiological context, therefore different development strategies will be required.
Rebecca Harris is an Assistant Professor in TB mathematical modelling and epidemiology at the London School of Hygiene and Tropical Medicine. Her research includes the development of mathematical models to assess the potential epidemiological impact of new TB vaccines in China, India and South Africa, and the development of a novel low-cost app for spatial mapping of TB in low income settings to support the design of TB vaccine studies and public health programmes. Her area of specialisation is epidemiology and mathematical modelling to inform mid-to-late stage development of TB vaccines.
She was awarded an MBioch in Molecular and Cellular Biochemistry and an MSc in Global Health from the University of Oxford in 2008 and 2009, respectively, and a PhD in epidemiology and mathematical modelling from LSHTM in 2017. From 2009 to 2013, as Technical Officer in the Global Influenza Programme of the World Health Organization, and subsequently as a consultant Epidemiology Manager at GlaxoSmithKline Vaccines, her research has spanned influenza, tuberculosis, malaria, neglected tropical diseases and emerging infectious diseases.