Advances in human clinical trials of vaccines to prevent HIV/AIDS and other HIV prevention interventions

Exploring evidence for behavioral risk compensation among participants in an HIV vaccine clinical trial

BACKGROUND

HIV vaccine trial participants may engage in behavioral risk compensation due to a false sense of protection. We conducted an ancillary study of an HIV Vaccine Trials Network (HVTN) vaccine efficacy trial to explore risk compensation among trial participants compared to persons who were willing to participate but ineligible based on previous exposure to the Ad5 virus (Ad5+) across three timepoints.

METHODS

Participants were drawn from the Atlanta, GA site of the HVTN 505 vaccine trial. From 2011-2013, all persons who met prescreening criteria for the clinical trial and presented for Ad5 antibody testing were invited to participate in the ancillary study. Data were collected from vaccine trial participants (n=51) and Ad5+ participants (n=60) via online surveys across three timepoints: baseline, T2 (after trial participants received 2/4 injections) and T3 (after trial participants received 4/4 injections). Data analyses assessed demographic, psychosocial, and behavioral differences at baseline and changes at each timepoint.

RESULTS

At baseline, Ad5+ participants were less likely to have some college education (p=0.024) or health insurance (p=0.008), and were more likely to want to participate in the vaccine trial "to feel safer having unprotected sex" (p=0.005). Among vaccine trial participants, unprotected anal sex with a casual partner (p=0.05), HIV transmission worry (p=0.033), and perceived chance of getting HIV (p=0.027), decreased across timepoints.

CONCLUSIONS

Study findings suggest that persons with previous exposure to Ad5 may be systematically different from their Ad5-negative peers. Unprotected anal sex with a casual partner significantly decreased among HIV vaccine trial participants, as did HIV worry and perceived chance of getting HIV. Findings did not support evidence of risk compensation among HIV vaccine trial participants compared to Ad5+ participants.

Safety reporting in developing country vaccine clinical trials-a systematic review

With more vaccines becoming available worldwide, vaccine research is on the rise in developing countries. To gain a better understanding of safety reporting from vaccine clinical research in developing countries, we conducted a systematic review in Medline and Embase (1989-2011) of published randomized clinical trials (RCTs) reporting safety outcomes with ≥50% developing country participation (PROSPERO systematic review registration number: CRD42012002025). Developing country vaccine RCTs were analyzed with respect to the number of participants, age groups studied, inclusion of safety information, number of reported adverse events following immunization (AEFI), type and duration of safety follow-up, use of standardized AEFI case definitions, grading of AEFI severity, and the reporting of levels of diagnostic certainty for AEFI. The systematic search yielded a total number of 50 randomized vaccine clinical trials investigating 12 different vaccines, most commonly rotavirus and malaria vaccines. In these trials, 94,459 AEFI were reported from 446,908 participants receiving 735,920 vaccine doses. All 50 RCTs mentioned safety outcomes with 70% using definitions for at least one AEFI. The most commonly defined AEFI was fever (27), followed by local (16) and systemic reactions (14). Logistic regression analysis revealed a positive correlation between the implementation of a fever case definition and the reporting rate for fever as an AEFI (p=0.027). Overall, 16 different definitions for fever and 7 different definitions for erythema were applied. Predefined AEFI case definitions by the Brighton Collaboration were used in only two out of 50 RCTs. The search was limited to RCTs published in English or German and may be missing studies published locally. The reported systematic review suggests room for improvement with respect to the harmonization of safety reporting from developing country vaccine clinical trials and the implementation of standardized case definitions.

Lentiviral vectors for immunization: an inflammatory field

Lentiviruses are retroviruses that are able to transduce both dividing and nondividing cells. Dendritic cells are key players in the innate and adaptive immune responses, and are natural targets for lentiviruses. Lentiviral vectors (LVs) have recently reached the clinical gene therapy arena, prompting their use as clinical vaccines. In recent years, LVs have emerged as a robust and practical experimental platform for gene delivery and rational genetic reprogramming of dendritic cells. Here, we present the status quo of the LV system for protective or therapeutic vaccine development. This vector system has been extensively evaluated for ex vivo and in vivo (immuno)gene delivery. Improvements of the LV design in order to further grant a higher biosafety profile for vaccine development are presented.