Additionally, there were no supplementary immunization activities (vaccination campaigns) for measles conducted in Sri Lanka during the period of the trial. Ongoing transmission of measles is Akt inhibitor unlikely to have contributed to the increases

in seropositivity, as Sri Lanka has maintained very high rates of measles vaccination among infants since 2000 [8], and there were no known/reported outbreaks of measles in the District of Colombo during the study period. And finally, unrecognized measles transmission would have had to occur at very high community attack rates in infants (e.g. 90%), as we found long-term increases in anti-measles IgG after 28 days post-vaccination in nearly all infants in the study. Few studies have prospectively measured measles antibody responses so long after vaccination with a single dose of measles vaccine at 9 months of age, but studies in the Gambia [9] and [10] (measles vaccine co-administered with yellow fever vaccine) and Malawi STAT inhibitor [11] (measles vaccine given alone) have made similar findings of continually increasing measles immune responses at 9–15

months post-vaccination in the absence of identified measles outbreaks and with “no explanation for this trend” [10]. Regarding our findings for the immune response to JE, these results are similar to those obtained in a study among 9-month-old infants in the Philippines in which measles vaccine and LJEV were administered concomitantly [5] and [12]. The seropositivity to JE measured at one month was nearly identical in the Sri Lankan and Philippine infants (90.7% vs 90.5%, respectively), although the JE GMTs were somewhat lower in the Sri Lankan infants (111 vs 155, respectively). The significance

of the TCL lower GMTs are uncertain, given that GMTs in both populations are well above the WHO-recommended threshold of protection of a 1:10 dilution in a 50% PRNT assay [4]. It is reassuring that 1 year following administration of the vaccine, JE antibody concentrations were well-maintained in Sri Lankan children. In studies in infants and young children that have measured the response to LJEV alone, seropositivity rates post-vaccination have ranged from 86% in Bangladesh [13], to 92% in the Philippines [5], to 95% in Thailand [14] and 96% in Korea [15]. A key limitation of this study was that there was not a control group followed in parallel to strengthen interpretation of immunogenicity and safety. Additionally, we measured seropositivity for measles antibodies using ELISA, which does specifically measure neutralizing antibodies; only results from PRNT for measles are considered truly indicative of seroprotective responses to measles [16].