Which is the MS Access  role  in medical database applications?

Access is a productive and very customizable database for small practices and comes with MS Office (or standalone). The next step up in a medical environment would be MS SQL Server. MS SQL Server is used mainly in Hospitals. Medical office usually only has need of a small application and the added functionality with MS SQL Server, comes with a heavy price.

Software packages built in MS Access are very flexible and can be easily modified as medical office requirements and processes change

Microsoft Access can handle up to 12-18 simultaneous connections in a networked environment and unlimited concurrent connections, as long as those connections remain under the process limit.  For a medical office usually 5-9 simultaneous connections  is more than enough