Antibody responses after dose-sparing intradermal influenza vaccination.

Reduced-dose intradermal (ID) influenza vaccination is an attractive approach to increase availability of vaccine supply in an event of vaccine shortage. We conducted a randomized open-label study, in which 500 subjects were randomly assigned to receive an ID injection of 0.1 ml dose of inactivated split-virion influenza vaccine or an IM injection of 0.5 ml dose. The subjects who had hemagglutination inhibition (HI) antibody titer of at least 1:40 at day 28 post-vaccination in ID and IM groups were 93.3% versus 98.0% for influenza A(H1N1) virus, 86.3% versus 95.0% for A(H3N2) virus, and 43.5% versus 57.0% for influenza B virus. Subjects in the ID group had an increase in geometric mean titer by a factor of 16 for the H1N1 strain, 8 for the H3N2 strain, and 2 for the B strain on day 28, as compared with respective increase in the IM group of 31, 20, and 3. Local reactions were significantly more frequent among subjects in the ID group than those in the IM group, but the reactions were mild and transient. In this study, ID administration of one-fifth dose of influenza vaccine elicited significantly lower levels of antibody response as compared to full-dose IM injection. However, the antibody responses elicited by the ID vaccination were still sufficiently high to meet the requirement guidelines of the European Committee for Proprietary Medicinal Products (CPMP) for the annual relicensure of influenza vaccines.

Behavioral and social issues among volunteers in a preventive HIV vaccine trial in Thailand.

Behavioral and social issues were investigated in 363 phase I/II preventive HIV-1 vaccine trial volunteers in Thailand. These issues included risk behavior, HIV knowledge, distress, and social consequences of vaccine trial participation. Data were collected at baseline and at 4-, 8-, and 12-month follow-up visits. Volunteers reported relatively low levels of risk behaviors at baseline and at follow-up. Overtly negative reactions from family or friends were reported by 5.9%. No experiences of discrimination in employment, health care, or insurance were reported. Mean levels of distress were low throughout the trial, and HIV-related knowledge was high, although it was common to consider the possibility of HIV transmission through casual contact. Findings add to the evidence that preventive HIV vaccine trials are feasible in Thailand.

Recruiting volunteers for a multisite phase I/II HIV preventive vaccine trial in Thailand.

Factors believed to be predictive of retention through the recruitment and screening processes for preventive HIV trials were investigated in a large multisite phase I/II HIV vaccine trial in Thailand. Retention through recruitment was equal to or greater than in previous smaller trials with similar populations. The data suggested that recruitment proceeded in a stepwise manner with different influences at each step. Demographic and motivational variables were most important in predicting retention in making and keeping screening appointments. Altruistic or mixed altruistic and nonaltruistic motives were associated with greater retention. Laboratory/medical variables appeared to be the main influence on retention during screening, although some volunteers withdrew for different reasons. The frequent presence of mixed (altruistic and nonaltruistic) motives at initial contact suggests that motivation for trials is more complex than has been previously acknowledged.