An Ethical Justification for Expanding the Notion of Effectiveness in Vaccine Post-Market Monitoring: Insights from the HPV Vaccine in Canada

Health regulators must carefully monitor the real-world safety and effectiveness of marketed vaccines through post-market monitoring in order to protect the public's health and promote those vaccines that best achieve public health goals. Yet, despite the fact that vaccines used in collective immunization programmes should be assessed in the context of a public health response, post-market effectiveness monitoring is often limited to assessing immunogenicity or limited programmatic features, rather than assessing effectiveness across populations. We argue that post-market monitoring ought to be expanded in two ways to reflect a 'public health notion of post-market effectiveness', which incorporates normative public health considerations: (i) effectiveness monitoring should yield higher quality data and grant special attention to underrepresented and vulnerable populations; and (ii) the scope of effectiveness should be expanded to include a consideration of the various social factors that maximize (and minimize) a vaccine's effectiveness at the population level, paying particular attention to how immunization programmes impact related health gradients. We use the case of the human papillomavirus vaccine in Canada to elucidate how expanding post-market effectiveness monitoring is necessary to close the gap between clinical practice and public health, and to ensure that vaccines are effective in a morally relevant sense.