This study compares the timing of the rise and decline of measles-specific IgM in serum
samples and in oral fluid samples. Two hundred and eighty 9-month-old infants presenting for
routine measles vaccination in Addis Ababa, Ethiopia, were enrolled. Paired serum and oral
fluid samples were collected before and 1, 2, 3 or 4 weeks after measles vaccination. Samples
were tested by using a modified antibody-capture enzyme immunoassay. For the 321 IgM-negative pre- and post-vaccination serum samples, 317 (99%) of their corresponding oral fluid
samples were IgM-negative. Among the 130 IgM-positive serum samples, 75% of their paired
oral fluid samples were IgM-positive, with the percentage rising to 87% after oral fluid samples
collected [ges ]3·5 weeks after vaccination were excluded. Among the post-vaccination serum
samples, the percent IgM-positive peaked in week 3 and declined to 79% in week 4. For post-vaccination oral fluid samples, the percent IgM-positive peaked in weeks 2 and 3, and then
declined to 43% in week 4. This modified antibody-capture enzyme immunoassay appears to
detect vaccine-induced measles-specific IgM in the first 3 weeks after vaccination.