Differential immune responses to primary measles-mumps-rubella vaccination in Israeli children.

Measles remains an important cause of morbidity and mortality worldwide, primarily due to problems associated with delivery of the live attenuated vaccine to susceptible populations. In some developed countries, there is concern about the effects of immunization on the immune system. In this study, we analyzed the responses of 12-month-old Bedouin and Jewish children living in Israel to routine measles-mumps-rubella (MMR) vaccination. Seroconversion to measles was 99% in Bedouin and 79% in Jewish children (P < 0.01), and that to mumps and rubella was 92 to 100% in both groups. Measles neutralizing antibody titers were higher in Bedouin (333 +/- 39 mIU/ml) than Jewish (122 +/- 60 mIU/ml) children (P < 0.002). Immunoglobulin G levels were higher in Bedouin than Jewish children (P = 0.007) and increased after vaccination (P = 0.0009). Leukocyte (P < 0.02) and lymphocyte (P = 0.04) counts were higher and CD4 lymphocyte percentages were lower (P < 0.001) in Bedouin than Jewish children before and after vaccination. Leukocyte counts and natural killer cell numbers did not change after vaccination, but lytic activity increased in Bedouin children (P < 0.005). Spontaneous proliferation of cultured peripheral blood mononuclear cells increased with vaccination, but there were no changes in the proliferative responses to phytohemagglutinin or tetanus toxoid. In summary, no adverse effects of MMR vaccination on immune function were detected. However, there were differences in underlying immunologic parameters and in response to the measles component of the vaccine between Bedouin and Jewish children. It is not known whether genetic differences or environmental exposure accounts for these differences.

The effect of measles-mumps-rubella (MMR) immunization on the immune responses of previously immunized primary school children.

Current policies for measles control call for administration of a second dose of vaccine to immunize those who failed to respond to the initial dose and to boost the responses of those with low levels of antibody. However, there has been concern expressed publicly that reimmunization may have adverse immunologic consequences. To determine the effects of reimmunization on immune responses, primary school children (N=38, mean age=6.14+/-0.35 years) with documented previous measles-mumps-rubella vaccine (MMR) immunization during infancy 4-5 years earlier were studied before and 1 month after receiving MMR as a part of routine reimmunization in Beer-Sheva, Israel. A substantial number of children were seronegative to measles (24%), mumps (34%) and rubella (44%). On reimmunization all seroconverted to mumps and rubella and all but one (92%) seroconverted to measles. The geometric mean titer of measles virus neutralizing antibody increased from 171 to 724 and the greatest increases occurred in those with the lowest pre-immunization titers. Moderate increases in levels of total IgM, IgG and IgE were detected in those with increases in antibody to measles virus. After reimmunization leukocyte counts decreased significantly from (5.8 x 10(6))+/-2.3 to (3.4 x 10(6))+/-0.7 ml(-1) (P=0.0001). The percentages of both CD4(+) and CD8(+) T cells decreased while the CD4:CD8 ratio remained unchanged. The percentage of CD56(+) natural killer (NK) cells increased from 5.2+/-2.7 to 7.2+/-2.8 (P=0.01). Functional assays showed improved lymphoproliferation in response to stimulation with phytohemagglutinin and tetanus toxoid and stable NK lytic activity. Therefore, reimmunization was accompanied by decreased leukocyte counts, but leukocyte function was unchanged or improved.