Measles vaccination of infants in a well-vaccinated population.
During outbreaks of measles, measles vaccine is recommended for infants considered to be at risk who are 6 months of age and older. In a prospective trial the serologic response to early measles immunization has been evaluated in 125 infants given monovalent measles vaccine at 6 to 8.5 months of age and measles-mumps-rubella at 15 months. The response to vaccination was measured by plaque reduction neutralization (PRN) assay and enzyme immunoassay. Infants were grouped by the mother's immunization history: natural immunity (n = 60, Group 1); killed followed by live, further attenuated vaccine (n = 22, Group 2); and live, further attenuated vaccine only (n = 43, Group 3). The prevaccination geometric mean titer (GMT) by PRN for Group 1 (GMT = 69) was significantly higher than that of Group 2 (GMT = 18) or 3 (GMT = 13). Seroconversion (4-fold increase in PRN titer) rates after monovalent vaccine were 31, 71 and 76% for Groups 1, 2 and 3, respectively. Seroconversion percentages were higher when measured 6 to 8 weeks after vaccination compared with 4 to 5 weeks. After measles-mumps-rubella > or = 97% of all infants had PRN titers > 120 and were measles IgG-positive by enzyme immunoassay. These data show that as demographics shift to a well-vaccinated maternal population and susceptibility in younger infants, measles vaccination before the currently recommended age will be effective.
Carson
M M
MM
Department of Pediatrics, University of Alberta, Edmonton, Canada.
Spady
D W
DW
Albrecht
P
P
Beeler
J A
JA
Thipphawong
J
J
Barreto
L
L
Grimsrud
K M
KM
Pabst
H F
HF
D000367:Age Factors; D000914:Antibodies, Viral / Q000032:analysis; D004196:Disease Outbreaks / Q000517:prevention & control*; D005260:Female; D006801:Humans; D007112:Immunity, Maternally-Acquired; D007223:Infant; D008297:Male; D008458:Measles Vaccine / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology*; D011446:Prospective Studies
D000914:Antibodies, Viral; D008458:Measles Vaccine