BACKGROUND: Assessment of high-dose vitamin A supplementation (VAS) coverage often relies on postevent coverage (PEC) surveys, but the validity of these methods has rarely been evaluated. OBJECTIVES: To assess reported VAS coverage and factors associated with missed coverage and to investigate the reliability of the results. METHODS: During a cross-sectional survey, 10 454 caregivers of children <27 months old were asked whether their child had received VAS in the past 6 months. During a 48-week longitudinal study of 6232 children 6 to 30 months old, caregivers were asked every 4 weeks if their child had received VAS in the past 4 weeks. RESULTS: The cross-sectional study showed that 94.4% (95% confidence interval [CI]: 93.8%, 94.9%) of eligible children 6 to 26 months of age reportedly received VAS in the previous 6 months, as did 85.8% (CI: 84.5%, 87.2%) of ineligible, 0 to 5 months old children. The longitudinal study showed that 81.6% of children surveyed within 4 weeks following a VAS campaign reportedly received VAS during the campaign and 13.4% of caregivers incorrectly reported receiving VAS when no campaign had actually occurred. False-positive reporting was more likely when oral polio vaccine (OPV) was distributed during the reporting period (20.6% vs 5.4%; P < .001). Showing a photo of OPV during the interview reduced the odds ratio (OR) of false-positive reports (OR = 0.7 [0.6-0.8]). CONCLUSIONS: The PEC surveys should include children outside the target age to assess targeting efficiency, and pictures of both VAS and oral vaccines distributed during the same period should be shown during interviews to enhance reporting accuracy.
BACKGROUND: Assessment of high-dose vitamin A supplementation (VAS) coverage often relies on postevent coverage (PEC) surveys, but the validity of these methods has rarely been evaluated. OBJECTIVES: To assess reported VAS coverage and factors associated with missed coverage and to investigate the reliability of the results. METHODS: During a cross-sectional survey, 10 454 caregivers of children <27 months old were asked whether their child had received VAS in the past 6 months. During a 48-week longitudinal study of 6232 children 6 to 30 months old, caregivers were asked every 4 weeks if their child had received VAS in the past 4 weeks. RESULTS: The cross-sectional study showed that 94.4% (95% confidence interval [CI]: 93.8%, 94.9%) of eligible children 6 to 26 months of age reportedly received VAS in the previous 6 months, as did 85.8% (CI: 84.5%, 87.2%) of ineligible, 0 to 5 months old children. The longitudinal study showed that 81.6% of children surveyed within 4 weeks following a VAS campaign reportedly received VAS during the campaign and 13.4% of caregivers incorrectly reported receiving VAS when no campaign had actually occurred. False-positive reporting was more likely when oral polio vaccine (OPV) was distributed during the reporting period (20.6% vs 5.4%; P < .001). Showing a photo of OPV during the interview reduced the odds ratio (OR) of false-positive reports (OR = 0.7 [0.6-0.8]). CONCLUSIONS: The PEC surveys should include children outside the target age to assess targeting efficiency, and pictures of both VAS and oral vaccines distributed during the same period should be shown during interviews to enhance reporting accuracy.