Editorial: Increasing Human Mpox Cases: A Signal for Potential Re-emergence of Smallpox?

Abstract

Since 2022, Mpox has surged to a global scale, with nearly 100,000 cases reported by June 2024. This resurgence predominantly affects individuals under 45, born during or after the cessation of smallpox vaccination. Epidemiological evidence confirms that smallpox vaccines offer over 80% protection against Mpox. The rise in Mpox cases appears to be driven by a cocktail of factors which include the emergence of new MPXV strains, a dwindling population of previously smallpox vaccinated individuals, and an increasing number of individuals unvaccinated against smallpox. Although those vaccinated over 40 years ago retain significant immunity, studies suggest a concerning annual decline of 1.29%. Given these dynamics - rising Mpox cases linked to declining head immunity against smallpox and a growing naïve population - the scenario raises a critical question: Are we on the brink of a smallpox re-emergence? However the question is answered, it is imperative to address these issues urgently by conducting large-scale investigations to understand the residual immunity against smallpox and refine vaccination strategies. The recent resurgence of measles highlights how swiftly diseases once under control can reappear when vaccination coverage declines.