iOS Critical Alert notification: Vibrate for certain time to alert deaf persons

We are entitled by Apple for critical alerts.

Our app is an alerting app which shall now be used to alert deaf persons.

We did not find the possibility to alert deaf persons, by choosing vibration instead of sound.

The accessibility options of iOS don't seem to provide an option to choose vibration instead of sound. It does vibrate for a very short amount of time, but it must vibrate for at least 10-20 seconds to be of any help.

Is there any possibility to vibrate upon receiving a critical alert notification for that amount of time? We're also using a notification service extension, but we're more interested in an official solution, than a "hack" solution.
I second this. I would love to have the option to chose vibrate instead of sound for critical alerts. I use an Apple Watch while I'm sleeping, and I need to be able to have vibration for Critical Alerts when I am on-call for my work.

I have almost similar requirement for the diabetics app I am working on. I want to send a critical alert which vibrates 3 times. Did you find any solution?

iOS Critical Alert notification: Vibrate for certain time to alert deaf persons
 
 
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