Modelling study reveals long-term infection effects could push for higher vaccine coverage

A new research from UBC highlights how even minor post-infection problems may significantly influence vaccine coverage policies, urging a broader view beyond immediate illness impacts.

A new modelling study from the University of British Columbia suggests that even relatively small health problems that follow infection can change the case for wider vaccine coverage.

Published in the Proceedings of the National Academy of Sciences, the research is designed to help public health officials weigh not just the immediate toll of infection, but also the longer-term consequences that can follow. Chadi Saad-Roy, an assistant professor in UBC’s Department of Mathematics and Department of Microbiology and Immunology, said the findings show that “even small post-infection costs can tip the scales and make the case for vaccine-driven elimination”.

The work comes against the backdrop of growing evidence that infections can leave lasting effects. The COVID-19 pandemic brought that reality into sharp focus, with more than 400 million people worldwide reporting persistent symptoms often described as long COVID. Yet, as the UBC team notes, many models used to guide disease policy still focus mainly on the acute phase of illness rather than the burden that can remain after recovery.

To address that gap, the researchers built mathematical models that combine epidemiology and economics. The calculations take into account the costs of vaccination, including development, production, distribution and recruitment, alongside the costs of acute illness and longer-term complications such as hospital care and lost labour. The team tested several vaccine-cost patterns, including scenarios in which it becomes harder to reach additional people as coverage rises, as well as ones in which peer influence makes uptake easier over time.

According to the UBC analysis, non-pharmaceutical measures such as masking, distancing and air filtration also matter because they reduce transmission and, over time, lower the share of people who may later experience post-infection effects. The researchers found that, in every scenario they modelled, the ideal level of vaccine coverage was highly sensitive to post-acute illness, with even modest long-term costs pushing the optimum towards higher uptake and, in some cases, towards elimination.

Prakhar Jaiswal, a graduate student at UBC and the study’s first author, said reducing vaccine hesitancy could be decisive because it lowers the cost of reaching higher coverage. Saad-Roy added that long-term symptoms should not be dismissed as anecdotal and argued that larger, longer follow-up studies are needed to track them more systematically. The team said the broader lesson is that public-health planners must judge vaccine strategy in light of local behaviour, costs and disease burden rather than relying on acute infection alone.