Ill health
Start with the scheme booklet and see what that says. Even better if you have a copy of the scheme rules.
In general, if you go on early retirement you will get a proportionate benefit. In your case this might be 22/43 times 66%. Generally this will be reduced further to allow for the fact that you are getting the pension 20 years early. The common reduction is circa 4% for each year.
HOWEVER, if the eary retirement is because of ill health, and you can prove such, some schemes will not impose any reduction. But it depends on the scheme rules.