Effect of Second Dose of Measles Vaccine on Measles Antibody Status: A Randomized Controlled Trial.

ABSTRACT

Objective: To evaluate the effect of the second dose of measles vaccine on measles antibody status during childhood. Setting: Immunization centre of Under-five Clinic of the Department of Community Medicine at a tertiary-hospital. Design: Randomized Controlled trial. Methods: Blood samples were collected from all subjects for baseline measles serology by heel puncture at 9-12 months of age. All subjects were given the first dose of measels vaccine. At second visit (3-5 months later), after collecting the blood sample from all, half the children were randomized to receive the second dose of measles vaccine (study group), followed by collection of the third sample six weeks later in all the subjects. Results: A total of 78 children were enrolled and 30 children in each group could be analyzed. 11(36.6%) children in the study group and 13 (43.3%) children in the control group had protective levels of measles IgG at baseline. Around 93.3 % of children in the study group had protective measles antibody titers as against 50% in the control group at the end of the trial. The Geometric Mean Titre (GMT) of measles IgG increased from 14.8 NTU/mL to 18.2 NTU/mL from baseline to six weeks following receipt of the second dose of the vaccine in the study group, as compared to a decrease from 16.8 NTU/mL to 12.8 NTU/mL in the control group. Conclusions: A second dose of measles vaccine boosts the measles antibody status in the study population as compared to those who receive only a single dose.