This chronology of facts has challenged public health systems worldwide and regulatory bodies are no exception. Regulatory authorities with mechanisms in place to authorize the use of investigational products had to development guidelines and procedures, create task forces and alliances to maximize the efficiency of assessment, review and authorizations of medical products. Vaccines are undoubtedly the most complex medical products to develop, from concept to a stage where sufficient evidence of quality, safety and efficacy are collected to provide an assurance that their use will provide more benefits than risks when used in the context of a public health emergency.