Why the evolution of vaccine resistance is less of a concern than the evolution of drug resistance

Abstract

Vaccines and antimicrobial drugs both impose strong selection for resistance. Yet only drug resistance is a major challenge for 21st century medicine. Why is drug resistance ubiquitous and not vaccine resistance? Part of the answer is that vaccine resistance is far less likely to evolve than drug resistance. But what happens when vaccine resistance does evolve? We review six putative cases. We find that in contrast to drug resistance, vaccine resistance is harder to detect and harder to confirm and that the mechanistic basis is less well understood. Nevertheless, in the cases we examined, the pronounced health benefits associated with vaccination have largely been sustained. Thus, we contend that vaccine resistance is less of a concern than drug resistance because it is less likely to evolve and when it does, it is less harmful to human and animal health and well-being. Studies of pathogen strains that evolve the capacity to replicate and transmit from vaccinated hosts will enhance our ability to develop next-generation vaccines that minimize the risk of harmful pathogen evolution.

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“…A better understanding of MDV virulence factors will also allow a more focused development of novel MDV vaccines. Mechanisms of vaccine resistance should be addressed as this poses a constant risk to the poultry industry [18,19]. Moreover, future research should investigate why the ongoing evolution of virulence leading to failure of the CVI988 vaccine has not emerged as a significant industry problem yet.…”

“…Moreover, vaccinated chickens are still susceptible to infection with MDV field strains and shed these into the environment [14]. These 'imperfect' vaccines allow the virus to evolve and acquire a higher virulence [18,19].…”

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On biological evolution and environmental solutions

“…Increasingly, researchers can track disease dynamics over time by comparing genetic variation among isolates, and such data can help inform policy decision and management of viral diseases, such as COVID-19 (Andersen et al, 2020, Brüssow, 2020 and Ebola (Mbala-Kingebeni et al, 2019). Drug treatment is often the default approach used to control emergent bacterial and fungal diseases, but in some cases a single new drug can cause strong natural selection, and, combined with the high evolutionary potential of pathogens, this means that the expected time until drug resistance evolves can be short (Fisher et al, 2018;Kennedy and Read, 2018). For such scenarios, we need to develop evolution-aware strategies to avoid and control emergent diseases.…”