Looking for a sub to do this, thanks for any help

Data in cols A and B in Sheet1 (Data is sorted by col A)
ID_A Val_1
ID_A Val_2
ID_B Val_3
ID_B Val_4
etc

Desired Output in a new sheet, cols A and B, with multiple results per ID separated by comma
ID_A Val_1,Val_2
ID_B Val_3, Val_4