I'm interested in severe respiratory pandemics. Two examples:
Personal Protective Equipment (PPE) is basically masks and eye-protection, but there's more:
If used by many & depending on setting and circumstances, PPE can help a lot: reducing spread, maybe even extinguising outbreaks; and reducing the inoculum, maybe reducing severity for the infectee.
They are not perfect at this point. They seem to provide more protection for those around the user than for the user herself. Of course it's better if both of us use them.
Until perfect PPE are used, they need to be combined with reduction in the number of respiratory contacts and physical distance.