 Solution

Set the availability indicator $Y_i(t)$ to zero during the three-day recovery interval after each headache. Keep each episode's endpoint, but delay its entry to the previous headache time plus three. The calendar-time rows become

The first interval still begins at zero because the patient was already headache-free for at least seven days before treatment. The recovery gaps supply no at-risk exposure and no partial-likelihood risk-set membership; they should not be retained as ordinary event-free at-risk time. If recovery extends past administrative closure, no subsequent eligible interval is created. This is a refractory period in recurrent-event analysis, represented by availability rather than by changing the event times.