Methods
infection, death
REGRESSION, INFECTION, THROMBOEMBOLIC EVENT, CARDIAC EVENTS
This cohort study was a target trial emulation with pseudorandomization to control (without recent infection) vs 2 mutually exclusive exposures (most recent infection in preoperative days 1-30 or 31-60). Eligible patients underwent major surgery from January 1 to September 30, 2021 (Alpha and Delta strain prevalence). All participants were encouraged to receive vaccination, and policy was to test preoperatively using reverse transcription–polymerase chain reaction. No oral outpatient therapies were in use. The Veterans Affairs Boston institutional review board approved this study and approved a waiver of informed consent, as the risk to participants was considered minimal. The Time zero for pseudorandomization was preoperative day 60. A propensity score model and stabilized inverse probability of treatment weighting balanced characteristics across exposure groups. Propensity score covariates were factors known at time zero that would be associated with exposure and were considered balanced if standardized mean differences were less than 0.2. We did not assess infection severity.The end point was death, cardiac events, central nervous system outcomes, respiratory outcomes, surgical infection, or thromboembolic events within 30 days after surgery. Weighted logistic regression estimated the odds ratio (OR) of any outcome as a function of exposure group, perioperative factors (because they were not known at time zero), and any propensity score covariates unbalanced after weighting. The eMethods in 