Geoff Mercer Award – Trip Report by Gizem Mayis Bilgin

13 February 2024

by Gizem Mayis Bilgin

I attended EPIDEMICS9 – the 9th International Conference of Infectious Disease Dynamics in Bologna, Italy between the 28th of November and 1st of December 2023. I joined 820 participants representing 49 countries. I presented a poster combining two papers from my PhD which model the impact and cost-effectiveness of COVID-19 booster doses and oral antivirals in Fiji, Indonesia, Papua New Guinea, and Timor-Leste. I learned many things about infectious disease epidemiology, infectious disease modelling, and presenting at the conference.

On infectious disease epidemiology: I discovered the complexity of infection-derived immunity. Our immune responses to new strains of a virus are forever biased by the first strain we encountered in childhood – a concept known as ‘original antigenic sin’. The antigenic distance between two strains determines the strength of protection between the two. Cross-protection is asymmetrical for multiple pathogens, notably dengue, whereby infection with serotype X may give you stronger protection to serotype Y than visa versa. Cross-protection often fades rapidly after recovery, leaving protection only against the serotype with which you were infected. Adding further complexity, infection-derived immunity may blunt immune responses to vaccines. I wonder how these concepts apply to COVID-19, already a heterogenous immune landscape due to geospatial differences in circulation and multiple rounds of vaccination.

On infectious disease modelling: I reflected on the importance of communicating the assumptions and limitations of data underlying mathematical models. Modelling was given unprecedented visibility during the COVID-19 pandemic. This visibility came with public scrutiny on the usefulness, accountability, and transparency of modelling as evidence in public health. The Lancet have launched a commission on Strengthening the Usefulness of Epidemiological Modelling. I am interested to see how the creation of a framework, like the existing x guidelines for health economic evaluations, will enhance the policy impact of mathematical modelling.

On presenting: I learned why posters make good networking tools. I talked to twelve people within two hours – on my research, on their research, and the interaction between the two. I enjoyed the benefits of printing a poster on canvas. In the future I will include a picture of myself on the poster as I noticed many people moving to give me space to read my own poster, and others reading several name tags before finding me to ask a question.

I thank the NCEPH Scholarships Committee for supporting my attendance at EPIDEMICS9. I hope my contribution to the conference pays tribute to Geoff’s legacy in applying mathematics to infectious disease problems.

Link to the poster:

Link to my papers: &

Gizem Mayis Bilgin with her poster at the 9th International Conference of Infectious Disease Dynamics in Bologna, Italy.