[1] Johns Hopkins Univ, Bloomberg Sch Publ Hlth, Dept Int Hlth, Baltimore, MD 21218 USA
[2] Univ North Carolina Chapel Hill, Carolina Populat Ctr, Chapel Hill, NC 27599 USA
[3] Univ North Carolina Chapel Hill, Gillings Sch Global Publ Hlth, Dept Maternal & Child Hlth, Chapel Hill, NC 27599 USA
[4] Univ North Carolina Chapel Hill, Carolina Populat Ctr, MEASURE Evaluat, Chapel Hill, NC USA
[5] Univ North Carolina Chapel Hill, Gillings Sch Global Publ Hlth, Dept Epidemiol, Chapel Hill, NC USA