Surveillance of Infant Formula Shortages Using Special Supplemental Nutrition Program for Women, Infants, and Children Administrative Data.

To quantify self-reported difficulty accessing Special Supplemental Nutrition Program for Women, Infants, and Children (WIC)-issued infant formula among participants early in the coronavirus disease 2019 (COVID-19) pandemic, to determine if infant formula redemption was associated with self-reported difficulty accessing infant formula, and to quantify changes in formula redemption during the 2022–2023 US infant formula shortages. A cross-sectional study and time series data. Families participating in the WIC program in the Los Angeles metropolitan area from November 2019 to June 2023. Families with infants (aged 0–12 months) issued infant formula by WIC with a completed 2020 Los Angeles County WIC Survey (n = 1,897) or issued infant formula by a large WIC program in Southern California between November 2019 and June 2023 (n = 109,135). Incidence of ≥ 30% reduction in infant formula redemption and interval-scaled infant formula redemption. Special Supplemental Nutrition Program for Women, Infants, and Children formula redemption data were matched to 2020 Los Angeles County WIC Survey data to determine if self-reported difficulty accessing infant formula was associated with administrative infant formula redemption data using negative binomial regression and were used to quantify the prevalence and severity of incomplete formula redemption during 2020–2023 formula shortages using ordinal logistic regression (outcome: interval-scaled formula redemption). Few (13.0%) caregivers reported difficulty accessing the WIC-issued formula early in the COVID-19 pandemic. The 2.8% who reported an unresolved shortage early in the COVID-19 pandemic had 201% higher rates of ≥ 30% declines in formula redemption (incidence rate ratio [IRR], 3.01; 95% confidence interval, 1.57–5.79, P < 0.001) than those with no difficulties. Incomplete formula redemption odds were significantly elevated throughout the COVID-19 pandemic from March 2020 to January 2022 and increased further during the 2022–2023 infant formula shortages from February 2022 to June 2023, reaching 342% higher in October 2022 than February 2020 (odds ratio, 4.42; 95% confidence interval, 4.14–4.72; P < 0.001). Special Supplemental Nutrition Program for Women, Infants, and Children redemption data are an adequate proxy for population-level infant formula access issues among households with low income but are insufficiently sensitive for screening at a household level. US formula shortages (2020–2023) demonstrate the need for improved coordination between nutrition assistance programs, regulatory bodies, and commercial food systems, particularly during acute supply crises. [ABSTRACT FROM AUTHOR]