The inactivated purified hepatitis A vaccine that we tested is well tolerated, and a single dose is highly protective against clinically apparent hepatitis A.

Girls' school participation has expanded considerably in the developing world over the last few decades, a phenomenon expected to have substantial consequences for reproductive behaviour. Using Demographic and Health Survey data from 43 countries, this paper examines trends and differentials in the mean ages at three critical life-cycle events for young women: first sexual intercourse, first marriage, and first birth. We measure the extent to which trends in the timing of these events are driven either by the changing educational composition of populations or by changes in behaviour within education groups. Mean ages have risen over time in all regions for all three events, except age at first sex in Latin America and the Caribbean. Results from a decomposition exercise indicate that increases in educational attainment, rather than trends within education groups, are primarily responsible for the overall trends. Possible explanations for these findings are discussed. IntroductionA successful transition to adulthood includes adequate preparation for adult roles and the capacity to make informed decisions about the timing of key life events (Lloyd 2005). First sexual intercourse, first marriage, and first birth are among the most consequential of these events. Taking on the roles of sexual partner, spouse, and parent too early may undermine the success of this transition, jeopardize a young person's health and well-being, and have deleterious effects on the health and well-being of her offspring (Lloyd 2005). In lessdeveloped-country settings, where HIV is endemic and where young women suffer disproportionately from sexually transmitted infections (STIs), the earlier sex is initiated, the longer the exposure to the risk of infection. On average, the younger the age of a woman at marriage, the larger the age difference between spouses, the less agency women are reported to have within marriage, and the higher the likelihood of marital dissolution (Singh and Samara 1996;Mensch 2005). And finally, early childbirth, before achieving full physical maturity around age 16, is associated with a higher likelihood of maternal death (Blanc et al. 2013;Nove et al. 2014), infant death, and other poor child health outcomes (Finlay et al. 2011). Moreover, the timing of births has an effect on population growth. For all these reasons, there is considerable interest on the part of researchers and policymakers in trends that are the focus of this study: ages at first sex, marriage/union, and childbirth in the developing world.The paper begins with a review of the literature on the impact of women's schooling on fertility and on the timing of first sex, first marriage, and first birth. This is followed by a detailed empirical analysis of levels and trends in the ages at these life-cycle events, based on data collected by Demographic and Health Surveys (DHS) since 1986 in 43 less developed countries in Asia and Northern Africa, Latin America and the Caribbean, and sub-Saharan Africa. The mean ages at events are estimated with a meth...

The quality of drug data in the 1984 wave of the National Longitudinal Survey of Youth is explored. Comparisons with other national surveys indicate that underreporting of use of illicit drugs other than marijuana appears to have taken place, and that light users of these drugs are underrepresented among the self-acknowledged users. Comparison with marijuana use reported four years earlier indicates that experimental marijuana users are much less likely than extensive users to acknowledge involvement. Even after controlling for frequency of use, underreporting is more common among terminal high school dropouts and minorities. Not only individual characteristics but field conditions also contribute to underreporting. Familiarity with the interviewer, as measured by number of prior interviewing contacts, depresses drug use reporting. We speculate that interviewer familiarity increases salience of normative standards and that participants respond not only in terms of their past familiarity but also in terms of their subjective expectations regarding the probability of a future encounter with the interviewer.