Lauren Brown, MSc

Friday 30 June, 16:45 – 18:00

Abstract: Background & aims of study Quantifying immunity to poliovirus serotypes in the South African population is valuable to inform public health resource allocation, particularly in the context of recent and ongoing outbreaks in the region. We aimed to estimate district-level humoral and mucosal immunity to wild poliovirus type 1 (WPV1), in five-year age bands, for each of South Africa’s 52 districts. Methods & results We used data on annual doses of Oral Poliovirus Vaccine (OPV) and Inactivated Poliovirus Vaccine (IPV) administered at the district level between 2009 and mid-2022, live births in these years, population sizes, and a nationally representative serosurvey of young children conducted in 1995. We used a combination of bootstrapping and proxy measures where data on doses administered were incomplete. We simulated distribution of vaccine doses to the eligible population and then estimated immunity levels by birth year, assuming a per-dose efficacy of 76% for OPV and n-dose efficacies for people who received 1-4 IPV doses. Mucosal immunity levels for individuals born between the 1995 serosurvey and 2009 were extrapolated for each realization by fitting a straight line from the survey-estimated immunity level to the level estimated based on 2009 data. Our results highlight that immunity to WPV1 is highly heterogeneous across districts. These estimates are a key input for the South African Centre for Epidemiological Modelling and Analysis (SACEMA) poliovirus transmission model. Implications Our approach allows us to estimate immunity from imperfect data, is applicable to other poliovirus serotypes, and can be easily adapted to similar data-poor settings for other diseases. Future work will prioritize the investigation of immunity to poliovirus type 2 in South Africa, given the recent emergence of circulating vaccine-derived poliovirus type 2 in the region. Moreover, we are developing a robust and transparent tool that will enable us to estimate immunity to a wide range of pathogens in diverse settings. This tool will enable the user to provide valuable insights into the immunological landscape, thereby facilitating targeted interventions.

About: Lauren Brown is a Junior Researcher at SACEMA, mainly working on polio transmission modelling in Southern Africa and coordinating SACEMA's first policy modelling fellowship. She holds an MSc in Applied Mathematics, her thesis was entitled "Mathematical modelling of tuberculosis in South Africa - investigating the impact of interventions on population-level incidence and mortality". She holds a BSc degree in Biomathematics, majoring in Biochemistry and Applied Mathematics, and a BSc Honours degree in the same.