Background/Objectives: Fractional intradermal administration may offer a dose-sparing approach to dengue vaccination. This randomized pilot study explored the administration of a fractional intradermal second dose of TAK-003 and described immune responses and adverse events in dengue-seropositive adults. Methods: Both groups received a standard 0.5-mL subcutaneous first dose, followed approximately 90 days later by either a standard 0.5-mL subcutaneous second dose or a fractional 0.1-mL intradermal second dose. Twenty-four dengue-seropositive adults were randomized in a 1:1 ratio to the SC–SC or SC–ID group. Anti-dengue IgG and IFN-γ ELISpot responses to DENV peptide pools were assessed at baseline, day 30, and day 120. Immunogenicity analyses were exploratory. Results: All 24 vaccinated participants completed follow-up. Day-30 measurements followed the common subcutaneous first dose and preceded the different second-dose regimens. At day 120, median anti-dengue IgG levels were 141.30 and 146.60 RU/mL in the SC–SC and SC–ID groups, respectively. IFN-γ responses to the tested peptide pools were measurable in both groups. No statistically significant between-group differences were detected at day 120, although the small sample size precludes conclusions of similarity. No serious adverse events were observed. Conclusions: Fractional intradermal administration of the second TAK-003 dose elicited measurable humoral and cellular immune responses and supports the biological feasibility of this dose-sparing approach. Given the exploratory nature and small sample size of this pilot study, these findings warrant confirmation in larger studies.

In the absence of a definitive gold standard for diagnosing latent tuberculosis infection (LTBI) in healthcare workers (HCWs), alternative specific biomarkers are needed. This longitudinal cohort study with baseline testing evaluated the diagnostic performance of stimulated plasma interferon-γ inducible protein 10 (IP-10) for LTBI detection among HCWs in a high tuberculosis (TB)–burden setting, using interferon-γ release assays (IGRAs) as the reference standard. The study was conducted at Songklanagarind Hospital, Thailand, between 2021 and 2024, and included 64 healthy HCWs. Serum and stimulated plasma samples were collected, and IP-10 and IFN-γ concentrations were measured by ELISA. Nine HCWs (14.0%) were LTBI-positive. Stimulated plasma IP-10, but not serum IP-10, showed significant correlations with IFN-γ levels in TB1 ( r = 0.719) and TB2 ( r = 0.768; p < 0.0001) tubes. At cut-off values of ≥ 2,980.0 pg/mL for TB1 and ≥ 3,108.0 pg/mL for TB2, sensitivity was 100%, specificity was 96.0% and 94.5%, and overall accuracy was 96.8% and 95.3%, respectively. Based on either IGRA or stimulated plasma IP-10 cut-off levels, five of nine LTBI cases declined treatment; among these, one individual (20.0%) progressed to active pulmonary TB 16 months later. Stimulated plasma IP-10 shows high diagnostic performance for LTBI detection among HCWs and may serve as an alternative for LTBI screening in high–TB-incidence with universal BCG vaccination.