It is a requirement of the Eyfs to ensure assistants are suitable.

Once the DBS is done you need to check regularly to make sure their suitability has not changed.

You also need to check that people who live in their house are suitable - because they can be disqualified by association if they live with an unsuitable person.

I have written a sample suitability declaration form and put it here with further advice about medication changes that must be checked -

Childminders and staff suitability -

Hth