We have recently shown that mycobacteria-specific Th17 cells are also detectable in peripheral blood of M.tb-exposed humans 20. This population was distinct from specific Th1 cells. No data on the induction of specific T cells expressing IL-17 or GM-CSF after TB or other vaccination in humans have been published. Six candidate TB vaccines are currently undergoing clinical trials 21. Modified vaccinia Ankara-expressing Ag85A (MVA85A), a recombinant strain of modified vaccinia Ankara-expressing Ag85A from M.tb22, is the most advanced in the clinical development process. This vaccine, designed to enhance

BCG-induced immunity, was found to be safe and highly immunogenic in healthy adults from the UK 23, The Gambia 24 and South Africa 25. CP-690550 mouse MVA85A is the first novel TB vaccine to be tested in children, who are an important target population for vaccination. As

part of an age de-escalation strategy in a TB-endemic region, we evaluated and compared the safety of MVA85A ICG-001 mouse vaccination and characterized the induced T-cell responses in healthy, M.tb-naïve adolescents and children. Twenty six adolescents and 56 children were screened between November 2006 and January 2008. Twelve adolescents and 24 children, none infected with M.tb, were found eligible for vaccination. Demographic characteristics are presented in Table 1 and reasons for exclusion in Supporting Information Table 1. All adolescents completed the 364-day follow-up period. One participant missed a single scheduled visit. Two of the 12 adolescents did not enter a record on their many diary cards for all of the first 7 days post-vaccination, as had been requested. These two participants were able to recall symptoms during scheduled visits on days 2 and 7 after vaccination, when specifically questioned for possible adverse events, including those recorded on the diary cards. Among adolescents, 64 adverse events were recorded (Table 2): 61 (95%) were classified as mild and 3 (5%) as moderate; no severe or serious adverse events were recorded. The moderate events were all skin reactions at the vaccination

site. There was a median of six adverse events per participant. Fifty (78%) adverse events were local reactions at the vaccination site, which occurred in all participants. The reactions were most pronounced 2 days after vaccination; by day 7 post-vaccination 31 (62%) had resolved. Of the 19 (38%) local events that had not resolved by day 7, 15 (30%) had resolved by day 14, and the remainder by day 28. The majority of these more persistent events were desquamation and swelling. Systemic adverse events were infrequent, and comprised primarily arthralgia, headache and feeling feverish. There were no significant abnormalities in hematology or biochemistry parameters, measured 7 and 84 days after vaccination.