This is a follow up study from the published article entitled "Comparison of immunogenicity and safety of four doses and four double doses vs. standard doses of hepatitis B vaccination in HIV-infected adults: a randomized, controlled trial" by Chaiklang K, Wipasa J, Chaiwarith R, Praparattanapan J, Supparatpinyo K. that was published in PLoS One. 2013 Nov 12;8(11):e80409. doi: 10.1371/journal.pone.0080409. eCollection 2013. ClinicalTrials.gov; NCT1289106. This study aimed to evaluate the efficacy of the HBV vaccination regimens using either four standard doses or four double doses compared with the current standard regimen of three doses in HIV-infected adults in northern Thailand. In addition, the investigators evaluated the efficacy of the HBV vaccination with the current standard regimen of three doses between healthy adults and HIV-infected patients.