In reply: Katelaris and colleagues raise concerns that uncontrolled before‐and‐after studies are vulnerable to bias and that other factors (eg, the severity of influenza) may have confounded our findings.1 I agree that uncontrolled before‐and‐after studies, being observational studies, are generally prone to different types of bias and that other residual (unmeasured) factors may have confounded our study outcomes.2
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