From one-size-fits-all to context-specific: the 10-day observation rule-a need for change.

WHO's 'Zero by 30' strategic plan relies on post-exposure prophylaxis guidelines designed for high-resource settings. This policy brief argues that the implementation gap of the 10-day observation rule in high-burden countries stems from fundamental infeasibility, exposing two paradigm defects in WHO guideline development: one-size-fits-all thinking and insufficient attention to implementation science. When the public misinterprets the 10-day rule as "wait and see" rather than "initiate PEP immediately while observing the animal," three biological facts render this misinterpretation fatal: symptomatic rabies is nearly 100% fatal and untreatable; a single vaccine dose cannot promptly induce sufficient neutralizing antibodies; and the incubation period for craniofacial Category III bites can be as short as 5-10 days-shorter than the full observation window. Waiting for animal observation without initiating PEP during this window means missing the only opportunity for effective prevention. Evidence from multiple countries shows that the rule's preconditions are almost never met in settings where 95% of rabies deaths occur. This misinterpretation has led to preventable deaths and given rise to guideline-associated rabies phobia (GARP). We propose five revisions to refine-not discard-the rule. Reshaping the paradigm is an ethical prerequisite for achieving 'Zero by 30'.