Todd D. Swarthout (Netherlands)
University College London
Infection and Immunity
Dr Todd Swarthout is a Senior Research Fellow (Epidemiology) at University College London. His research interests are in understanding how to optimise vaccine schedules to reduce the burden of vaccine-preventable diseases in low-resourced high mortality settings, how best to protect vulnerable groups, and how to optimise methods to evaluate vaccine impact and effectiveness. Todd obtained his MSc (Public Health in Developing Countries) from the London School of Hygiene and Tropical Medicine in 2002 and his PhD (Epidemiology) at University of Liverpool in 2021. He worked 12 years as an epidemiologist with Médecins Sans Frontiers (MSF) and Médecins du Monde (MDM), including 7 years as field epidemiologist in several locations on the African continent and as Senior Health Advisor during headquarter postings in Paris and Amsterdam. Prior to his work in Malawi, Todd worked with Novartis Vaccines in Amsterdam, leading the epidemiology portfolio in work to develop a GBS vaccine. Todd has worked as PI in Malawi since 2015 (permanently in the Netherlands since 2021) as lead of the Pneumonia and Meningitis Pathogens Research Group. This includes work on several studies funded by the Gates Foundation and the Wellcome Trust UK, including an evaluation of a 2+1 PCV schedule and work to evaluate PCV-induced serological profiles to assess the impact of the waning of serotype-specific antibody. Prior to his work in infectious diseases epidemiology, Todd trained in the field of Forestry and Natural Resource Conservation. Todd lived in rural coastal northern California, teaching field biology at an independent secondary school and leading a number of local environmental campaigns. One of these led to the 1999 creation of the Headwaters State Forest Reserve along California’s Redwood Coast.

Presenter of 1 Presentation

 Conference Calendar

O071 - RAPID WANING OF PCV13 VACCINE-INDUCED ANTIBODY AND PERSISTENT VACCINE SEROTYPE PNEUMOCOCCAL CARRIAGE AMONG CHILDREN UNDER-5-YEARS IN BLANTYRE, MALAWI, USING A 3+0 SCHEDULE: AN OBSEVATIONAL STUDY (ID 265)

Session Name
0740 - Parallel Session 09: Vaccine Impact (ID 63)
Session Type
Parallel Session
Date
Wed, 22.06.2022
Session Time
15:05 - 16:35
Room
Birchwood Ballroom
Presenter
Lecture Time
15:10 - 15:20

Abstract

Background

Pneumococcal conjugate vaccines (PCVs) induce serotype-specific IgG antibodies, effectively reducing vaccine serotype (VT) invasive pneumococcal disease (IPD), carriage and transmission. Following Malawi’s 2011 PCV13 introduction (3+0 schedule) we demonstrated substantial residual VT carriage among PCV-vaccinated children. To assess the hypothesis that vaccine-induced IgG wanes below levels associated with preventing carriage and disease, we investigated serotype-specific IgG dynamics through a pragmatic method of cross-sectional population-based immunogenicity profiling among PCV-vaccinated children aged <5 years.

Methods

Using 638 plasma samples, serotype-specific IgG to PCV13 VTs were measured using a standardised EIA and direct binding electrochemiluminescence-based methods in a WHO Reference laboratory. We developed a modelling framework using linear splines and censored regression to estimate population-averaged serological profiles. Leveraging carriage data, we estimated serotype-specific correlates of protection (CoP) against pneumococcal carriage.

Results

There was no consistent anti-serotype-3 vaccine response. Though diverse in profile, remaining VTs showed a vaccine-induced increase in IgG followed by rapid waning and then a subsequent increase, presumably due to natural exposure. The population-based age range at IgG nadir was 11.24 (19F & 23F) to 27.33 months (7F). IgG titres of 7 VTs waned temporarily (longest duration: 33.5 months, serotype-4) below the putative CoP for disease and 5 VTs did not attain CoP for carriage post-vaccination. Estimated CoP’s against VT carriage (0.50μg/mL - 2.5μg/mL) were higher than putative CoPs for IPD.

Conclusions

This pragmatic population-based method of serological profiling offers insights into serotype-specific immunity with important biological consequences for protection. When evaluating pneumococcal vaccine strategies, limiting early waning of VT immunity should be a priority.

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