Monkeypox: Can we count on the current smallpox immunization?

Two vaccines ACAM 2000 and JYNNEOS have obtained approval from the Food and Drug Administration as preventive measures against monkeypox, contributing significantly to the management of the monkeypox epidemic. Nonetheless, research has demonstrated that smallpox vaccination offers approximately 88.8% protection against monkeypox, while immunization with these vaccines generates relatively low levels of neutralizing antibodies. In this work, we performed a comprehensive comparison of antigens between the 2022-2023 monkeypox strains and the smallpox vaccine strains. Our analysis has revealed considerable amino acid changes in all 27 antigens, including core and envelope proteins. Amino acid substitutions within B cell epitopes were observed in 26 of these antigens, with at least half of the antigen substitutions occurring within B cell epitopes in 20 out of the 26 antigens analyzed. These findings may raise potential concerns regarding the efficacy of these vaccines.