Framing the willingness-to-pay question: impact on response patterns and mean willingness to pay.

In this study, respondents were randomly allocated to three variants of the payment card format and an open-ended format in order to test for convergent validity. The aim was to test whether preferences (as measured by willingness to pay additional tax) would be affected by framing the willingness-to-pay question differently. Results demonstrated that valuations were highly sensitive to whether respondents were asked to express their maximum willingness to pay per month or per year. Another important finding is that the introduction of a binary response filter prior to the payment card follow-up tends to eliminate the positive aspects of introducing a payment card and produces response patterns that are much in line with those of the open-ended contingent valuation format. However, although a filter will impact on the distribution of willingness-to-pay bids and on the rate of zero and protest bids, the overall impact on the welfare estimate is minor. The outcomes of this study indicate that valuations in the stated preference literature may be, at least in part, a function of the instrument designed to obtain the valuations.

The Effect of Smallpox and Bacillus Calmette-Guérin Vaccination on the Risk of Human Immunodeficiency Virus-1 Infection in Guinea-Bissau and Denmark.

BACKGROUND: The live smallpox and Bacillus Calmette-Guérin (BCG) vaccinations have been associated with better adult survival in both Guinea-Bissau and Denmark. In Guinea-Bissau, human immunodeficiency virus (HIV)-1 became an important cause of death after smallpox vaccination was phased out globally in 1980. We hypothesised that smallpox and BCG vaccinations were associated with a lower prevalence of HIV-1 infection, and we tested this hypothesis in both Guinea-Bissau and Denmark. METHODS: We conducted 2 studies: (1) a cross-sectional study of HIV infection and vaccination scars in Guinea-Bissau including 1751 individuals and (2) a case-base study with a background population of 46239 individuals in Denmark. In Guinea-Bissau, HIV-1 transmission was almost exclusively sexually transmitted. In Denmark, we excluded intravenous drug users. Data were analyzed using logistic regression. RESULTS: Bacillus Calmette-Guérin and/or smallpox vaccination compared with neither of these vaccines was associated with an adjusted odds ratio (aOR) for HIV-1 of 0.62 (95% confidence interval [CI], 0.36-1.07) in Guinea-Bissau and 0.70 (95% CI, 0.43-1.15) in Denmark. We combined the results from both settings in a meta-analysis (aOR = 0.66; 95% CI, 0.46-0.96). Data from Guinea-Bissau indicated a stronger effect of multiple smallpox vaccination scars (aOR = 0.27; 95% CI, 0.10-0.75) as follows: women, aOR = 0.18 (95% CI, 0.05-0.64); men, aOR = 0.52 (95% CI, 0.12-2.33); sex-differential effect, P = .29. CONCLUSIONS: The studies from Guinea-Bissau and Denmark, 2 very different settings, both suggest that the BCG and smallpox vaccines could be associated with a decreased risk of sexually transmitted HIV-1. It might be informative to pursue this observation and explore possible protective mechanisms as part of the search for an HIV-1 vaccine.

[Leisure time physical exercise during pregnancy and the risk of miscarriage: a study within the Danish National Birth Cohort--secondary publication]. / Motion under graviditeten og risikoen for spontan abort--sekundaerpublikation.

We investigated the association between exercise during pregnancy and risk of miscarriage among more than 90,000 pregnant women. Information on exposures was obtained by means of computer-assisted telephone interviews. A relation was found between the amount of exercise and the risk of miscarriage with the risk of miscarriage rising stepwise by the amount of exercise performed. Particularly "high impact exercise" was associated with an increased risk of miscarriage. No association was seen between exercise and risk of miscarriage after 18 weeks of gestation.

Vaccinia scars associated with improved survival among adults in rural Guinea-Bissau.

BACKGROUND: In urban Guinea-Bissau, adults with a vaccinia scar had better survival but also a higher prevalence of HIV-2 infection. We therefore investigated the association between vaccinia scar and survival and HIV infection in a rural area of Guinea-Bissau. METHODOLOGY/PRINCIPAL FINDINGS: In connection with a study of HIV in rural Guinea-Bissau, we assessed vaccinia and BCG scars in 193 HIV-1 or HIV-2 infected and 174 uninfected participants. Mortality was assessed after 2(1/2)-3 years of follow-up. The analyses were adjusted for age, sex, village, and HIV status. The prevalence of vaccinia scar was associated with age, village, and HIV-2 status but not with sex and schooling. Compared with individuals without any scar, individuals with a vaccinia scar had better survival (mortality rate ratio (MR) = 0.22 (95% CI 0.08-0.61)), the MR being 0.19 (95% CI 0.06-0.57) for women and 0.40 (95% CI 0.04-3.74) for men. Estimates were similar for HIV-2 infected and HIV-1 and HIV-2 uninfected individuals. The HIV-2 prevalence was higher among individuals with a vaccinia scar compared to individuals without a vaccinia scar (RR = 1.57 (95% CI 1.02-2.36)). CONCLUSION: The present study supports the hypothesis that vaccinia vaccination may have a non-specific beneficial effect on adult survival.