The effect of timing of sample collection on the detection of measles-specific IgM in serum and oral fluid samples after primary measles vaccination

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 ≥ 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 postvaccination 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.