The persistence of humoral and cellular immunities more than three decades after smallpox vaccination.

ABSTRACT

This study assessed the persistence of humoral (neutralising antibody titre to vaccinia virus) and cellular (immediate vaccinia-specific interferon (IFN)-gamma-producing T-cell) immunities to smallpox in a Korean population. Individuals who were vaccinated 25-60 years previously had higher neutralising antibody titres (geometric mean titre (GMT) 13.7; 95% CI 11.0-17.2) than vaccinia-naive individuals (GMT 6.7; 95% CI 5.5-8.0; p <0.001). However, there was no significant difference in cellular immunity between individuals vaccinated previously and vaccinia-naive individuals, and only 15% of the individuals vaccinated previously displayed an immediate IFN-gamma-producing effector-memory response in ELISPOT assays.