Humoral and cellular immune response after measles vaccination in Taiwan.

Measles immunoglobulin G (IgG) seroepidemiologic studies have been widely used to monitor the effectiveness of measles immunization programs in Taiwan. However, studies about cellular immunity against the measles virus have been lacking. This study surveyed cellular immunity after measles, mumps and rubella combined vaccine (MMR) immunization in Taiwan. Seventy six people between 1 and 80 years of age were enrolled. All patients lived in northern Taiwan, and none of them had immunodeficient disease. Every enrolled patient donated a tube of heparinized blood between January 2004 and June 2004 for cross-sectional studies of IgG seroepidemiologic and MMR-specific lymphoproliferative response. The results showed that the current 3-dose (measles x 1 + MMR x 2) measles immunization program induced slightly higher IgG seroprevalence (100% vs 85%, p=0.244) and a higher frequency of significant (stimulation indices > or = 3) MMR-specific lymphoproliferative response (50% vs 15%, p=0.044) than a 2-dose (measles x 1 + MMR x 1) immunization program, although there was no difference in IgG titers and stimulation indices. Furthermore, the population aged older than 36 years (pre-immunization era) had higher IgG titers and seroprevalence, and similar MMR-specific lymphoproliferative responses to that of the population aged younger than 36 years (post-immunization era). In summary, with the limited data, the current 3-dose (measles x 1 + MMR x 2) measles immunization policy probably more effectively induces humoral and cellular immunity than the 2-dose (measles x 1 + MMR x 1) policy. Measles IgG seroprevalence in populations of different age groups exceeds nearly 90%. Measles has been eliminated temporarily in Taiwan. For a better understanding of the durability of vaccine-induced immunity and in order to establish the most appropriate immunization schedule, long-term and large-scale prospective studies of measles-specific seroepidemiology and cellular immunity will be needed.