Methods to Adjust for Confounding in Test-Negative Design COVID-19 Effectiveness Studies: Simulation Study - Elizabeth AK Rowley; Patrick K Mitchell; Duck-Hye Yang; Ned Lewis; Brian E Dixon; Gabriela Vazquez-Benitez; William F Fadel; Inih J Essien; Allison L Naleway; Edward Stenehjem; Toan C Ong; Manjusha Gaglani; et al. (JMIR Formative Research)