Analysis of specific antibody and cellular immune response to first-dose measles vaccine Edmonston-Zagreb (EZ) in 9-month-old infants

Background: Measles vaccinations have been suggested to provide immune protection and decreased measles incidence. However, there was a limited study evaluating how the measles vaccine elicits specific immune responses.Objective: This study aimed to evaluate both humoral and cellular immunity to first-dose measles vaccine Edmonston-Zagreb (EZ) in 9-month-old Indonesian infants.Methods: A cohort study was conducted on 9-month-old infants who got the first-dose of measles vaccine EZ. Measles-specific immunoglobulin G (IgG) antibody serum levels were measured using plaque-reduction microneutralization assay. Peripheral blood mononuclear cells were stimulated with a measles-specific peptide to identify a cellular immune response. Quantification of CD4+ and CD8+ T-cells producing interferon-gamma (IFN-ɣ) and interleu-kin 17-A (IL-17A) were conducted by flow cytometry. Humoral and cellular immune response parameters were analyzed over time.Results: The prevalence of seropositivity rates was 85.8% at 1-month after vaccination and 16.67% at 6-months postvaccination. Measles-specific IgG antibodies increased significantly at 1-month after measles vaccination. However, they decreased significantly 6-months after vaccination. IFN-ɣ and IL-17A secreting T-cells increased significantly at 1-month after measles vaccination. Interestingly, a significant decrease of IFN-ɣ and IL-17A secreting CD4+ T cells was noticed 6-months postvaccination compared to IFN-ɣ and IL-17A secreting CD8+ T cells. Conclusion: Our study suggests that the first-dose measles vaccine on 9-months-old infants seems to induce both humoral and cellular immune responses that decline 6-months after vaccination.