Locating longitudinal study participants 10 years after last contact: Contemporary approaches to sample retention.

Aims: Despite their advantages, longitudinal studies often face high rates of attrition. This study documents the extensive efforts associated with retaining a longitudinal cohort last contacted 10 years earlier.

Method: We examine the processes and outcomes of attempts to reach 1736 individuals who have been part of a multiwave study about growing up in Ontario, Canada.

Planning and sustaining HIV response in the countries of the "risky middle".

This paper focusses on high-HIV middle-income countries termed the "risky middle", i.e. characterised by a typology based on HIV burden and gross national income (GNI), according to which seven countries - Lesotho, Eswatini, Kenya, Zimbabwe, Tanzania, Namibia and Zambia - are identified.