Background: Widespread smartphone use provides opportunities for mobile health HIV prevention strategies among at-risk populations. Objective: This study aims to investigate engagement in a theory-based (information–motivation–behavioral skills model) mobile phone app developed to support HIV pre-exposure prophylaxis (PrEP) adherence among Thai young men who have sex with men (YMSM) and young transgender women (YTGW) in Bangkok, Thailand. Methods: A randomized controlled trial was conducted among HIV-negative YMSM and YTGW aged 15-19 years initiating daily oral PrEP. Participants were randomized to receive either youth-friendly PrEP services (YFS) for 6 months, including monthly contact with site staff (clinic visits or telephone follow-up) and staff consultation access, or YFS plus use of a PrEP adherence support app (YFS+APP). The target population focus group discussion findings and the information–motivation–behavioral skills model informed app development. App features were based on the 3Rs—risk assessment of self-HIV acquisition risk, reminders to take PrEP, and rewards as redeemable points. Dried blood spots quantifying of tenofovir diphosphate were collected at months 3 and 6 to assess PrEP adherence. Tenofovir diphosphate ≥350-699 fmol/punch was classified as fair adherence and ≥700 fmol/punch as good adherence. Data analysis on app use paradata and exit interviews were conducted on the YFS+APP arm after 6 months of follow-up. Results: Between March 2018 and June 2019, 200 participants with a median age of 18 (IQR 17-19) years were enrolled. Overall, 74% (148/200) were YMSM; 87% (87/100) of participants who received YFS+APP logged in to the app and performed weekly HIV acquisition risk assessments (log-in and risk assessment [LRA]). The median duration between the first and last log-in was 3.5 (IQR 1.6-5.6) months, with a median frequency of 6 LRAs (IQR 2-10). Moreover, 22% (22/100) of the participants in the YFS+APP arm were frequent users (LRA≥10) during the 6-month follow-up period. YMSM were 9.3 (95% CI 1.2-74.3) times more likely to be frequent app users than YTGW (P=.04). Frequent app users had higher proportions (12%-16%) of PrEP adherence at both months 3 and 6 compared with infrequent users (LRA<10) and the YFS arm, although this did not reach statistical significance. Of the 100 participants in the YFS+APP arm, 23 (23%) were interviewed. The risk assessment function is perceived as the most useful app feature. Further aesthetic adaptations and a more comprehensive rewards system were suggested by the interviewees. Conclusions: Higher rates of PrEP adherence among frequent app users were observed; however, this was not statistically significant. A short app use duration of 3 months suggests that they may be useful in establishing habits in taking daily PrEP, but not long-term adherence. Further studies on the specific mechanisms of mobile phone apps that influence health behaviors are needed. Trial Registration: ClinicalTrials.gov NCT03778892; https://clinicaltrials.gov/ct2/show/NCT03778892

The heterosexual transmission of subtype E human immunodeficiency virus type 1 (HIV-1) infection was evaluated in 467 couples in Thailand in whom the man was HIV-1 positive and the woman had no risk factors for HIV other than sex with her infected partner. At baseline, 216 (46.3%) of the 467 women were positive for HIV-1: 52.2% had male partners with CD4⁺ lymphocyte counts of <200 cells/µL, 45.9% had partners with counts of 200–499, and 39.2% had partners with counts of ⩾500. Women were twice as likely to be HIV positive if their male partners had a history of a sexually transmitted disease (STD); however, their HIV prevalence was 29% among couples who had no STD history. We conclude that female partners of men infected with subtype E HIV-1 are at high risk of infection even when the man's CD4⁺ cell count is relatively high. A high rate of STDs may contribute significantly to this risk.

Introduction: Young men who have sex with men (YMSM) and young transgender women (YTGW) in Thailand are at high HIV risk. HIV self-tests (HIVSTs) are rapidly administrable and prompt linkage to HIV treatment or prevention services. This study assesses the acceptability and feasibility of blood-based HIVST use in adolescents. Methods: A cross-sectional study was conducted among YMSM and YTGW aged 15–19 years with HIV acquisition risk. Participants completed questionnaires on the HIVST and then administered INSTI® independently, an HIVST immunoassay detecting gp41 and gp36 antibodies from finger-stick blood. Confirmatory HIV antibody tests were performed. Results: Between July and September 2020, 90 adolescents were enrolled. Mean (SD) age was 17.6 (1.1) years. Half (N = 45) were YMSM. Forty-six (51%) were first-time HIV testers, and 32 (36%) had “ever used” HIV pre-exposure prophylaxis (PrEP). Two (2.2%, 95% CI: 0.0–5.3) tested positive, 21 (23.4%) invalid, and 67 (74.4%) negative. Invalidity causes included 17 (81%) insufficient blood, 3 (14%) buffer spillage, and 1 (5%) procedural missteps; all had negative HIV antibody tests. HIV self-test acceptability was 87.8% (95% CI: 81.0–94.5). Most (79%) preferred HIVST performance in hospital rather than at home. Conclusions: HIVSTs are acceptable in HIV at-risk adolescents. Blood-based HIVSTs should be positioned as rapid point-of-care tests with real-time linkage to HIV services.

This study aimed to assess long COVID, and describe immunogenicity against Omicron variants following BNT162b2 vaccination. A prospective cohort study was conducted among children (aged 5–11) and adolescents (aged 12–17) who had SARS-CoV-2 infection from July to December 2021 (Delta predominant period). Long COVID symptoms were assessed by questionnaires at 3 months after infection. Immunogenicity was evaluated by using a surrogate virus-neutralizing antibody test (sVNT) against the Omicron variant. We enrolled 97 children and 57 adolescents. At 3 months, 30 children (31%) and 34 adolescents (60%) reported at least one long COVID symptom, with respiratory symptoms prevailing (25% children and 32% adolescents). The median time from infection to vaccination was 3 months in adolescents and 7 months in children. At 1 month following vaccination, in children who received one-dose and two-dose BNT162b2 vaccines, the median (IQR) sVNT against Omicron was 86.2% inhibition (71.1–91.8) and 79.2% inhibition (61.5–88.9), respectively (p = 0.26). Among adolescents who received one-dose and two-dose BNT162b2 vaccines, the median (IQR) sVNT against Omicron was 64.4% inhibition (46.8–88.8) and 68.8% inhibition (65.0–91.2) (p = 0.64). Adolescents had a higher prevalence of long COVID than children. Immunogenicity against the Omicron variant after vaccination was high and did not vary between one or two doses of the vaccine in either children or adolescents.

Introduction: Tenofovir disoproxil fumarate with emtricitabine (TDF/FTC) is used for HIV pre‐exposure prophylaxis (PrEP). TDF may affect bone mineral density (BMD), particularly in youth who are at a stage of peak bone mass accrual. The objective of this study was to evaluate the effect of vitamin D and calcium supplementation on BMD among Thai youth receiving daily oral PrEP.Methods: This open‐label randomized trial was conducted in male youth aged between 15 and 24 years. Participants were randomized to Arm A who received once‐daily TDF/FTC plus vitamin D3 and calcium supplementation with meals twice daily (400 units of vitamin D3 and 1200 mg of elemental calcium/day) or Arm B who received once‐daily TDF/FTC only. PrEP users were defined as taking at least two tablets/week (tenofovir‐diphosphate level of >350 fmol/punch). Adherence to vitamin D/calcium supplementation was defined as self‐reported adherence of >50%. Lumbar spine (L2‐L4) BMD (LSBMD) was evaluated by dual‐energy X‐ray absorptiometry scan zero and six months after PrEP initiation.Results: From March 2019 to March 2020, 100 youth were enrolled. Baseline characteristics between the two arms were similar. Median (IQR) age was 18 (17 to 20) years. At entry, median (IQR) LSBMD z‐score was −0.8 (−1.5 to −0.3), 17% had low LSBMD (Z‐score < −2). The median amount of calcium intake from nutritional three‐day recall was 167 (IQR 94 to 272) mg/day, 39% of participants had vitamin D deficiency, defined as 25(OH)D levels 3% increase in LSBMD at month 6 compared to baseline (67.6% vs. 42.9% respectively; p = 0.03). There were significantly higher increases in LSBMD among youth with vitamin D deficiency who were supplemented; arm A + 0.05 (0 to 0.05) compared to arm B + 0.03 (−0.1 to 0.03), p = 0.04.Conclusions: Increases in LSBMD over six months among youth using PrEP who received vitamin D/calcium supplementation was greater than those not supplemented. Long‐term follow‐up should be considered to explore long‐term outcomes.