Short-term evolution of Mpox-specific IgG and neutralizing antibodies among individuals undergoing MVA-BN vaccination

The data on immune responses of individuals undergoing MVA-BN vaccination are scarce. We aimed to compare Mpox virus-specific antibody and neutralizing antibody responses among people with and without HIV receiving MVA-BN vaccines. This prospective study enrolled participants undergoing two-dose MVA-BN vaccination to investigate seroresponses after vaccination. Blood samples were collected before and after each dose of vaccination for determinations of anti-A29 and anti-H3 IgG. Neutralization tests were conducted for samples tested positive for both anti-A29 and anti-H3 IgG. Overall, 441 participants undergoing two-dose MVA-BN vaccination were enrolled. Seroconversion for anti-A29 and anti-H3 IgG, respectively, after the second dose of vaccination was 18.2% and 61.2%, 10.9% and 65.0%, and 51.6% and 90.6% among PWH, PWoH, and those who had had smallpox vaccination previously, respectively. About 20% of the participants with seroconversion lost seroresponses after a 7-month period of observation. None of the serum samples from vaccinated participants demonstrated neutralizing ability. Participants with previous smallpox vaccination had higher and more sustained antibody responses after receiving two doses of MVA-BN vaccines than those who had not undergone smallpox vaccination. More studies are warranted to assess the seroresponses to booster MVA-BN vaccination for vaccine non-responders or those having lost seroresponses.