Welfare of Animals in Experimental Vaccine Trials

Development of vaccines for human and animal diseases requires animal efficacy and safety testing, with specific welfare challenges in challenge models and adjuvant testing.

Key Facts

Vaccine development animal testing includes safety, immunogenicity, and challenge studies where animals are exposed to pathogens
Ferrets are the primary model for human influenza vaccine testing because their respiratory physiology approximates human infection patterns
The humane endpoint principle requires termination of experiments when animals reach predefined suffering thresholds, but implementation is inconsistent
COVID-19 vaccine development accelerated through the pandemic included animal studies in macaques, mice, and hamsters
Adjuvant testing for vaccine formulation can cause injection site pain and systemic inflammatory responses in test animals
Organoid and microphysiological systems are beginning to replace some animal vaccine testing steps for immunogenicity assessment

Welfare Considerations

Vaccine animal testing occurs in regulatory-mandated frameworks that have welfare protections built in, but implementation quality varies and the welfare costs are genuine. Challenge studies — where animals are intentionally infected with pathogens — are among the most welfare-intensive procedures in research, requiring especially rigorous humane endpoint monitoring. The rapid vaccine development during the COVID-19 pandemic demonstrated that animal testing timelines can be compressed without eliminating welfare standards. Sustained investment in validated alternatives to challenge models and more precise immunogenicity assays would reduce animal use and welfare costs in vaccine development.

What You Can Do

Support research into organoid and in vitro alternatives that can replace animal challenge models
Advocate for consistent and rigorously enforced humane endpoint protocols in vaccine animal testing
Engage with vaccine developers about their animal use reduction strategies
Learn about the regulatory frameworks governing vaccine animal testing in different jurisdictions
Support the NC3Rs and equivalent bodies funding vaccine testing alternative development