Since each type of microorganism has its own antibodies, Salk's vaccine contained all three polio virus types recognized at the time.
(each type of microorganism; has; its own antibodies) (Salk's vaccine; contained; all three polio virus types recognized at the time) (all three polio virus types; recognized; T:at the time)
each type of microorganism Salk's vaccine all three polio virus types
has contained recognized
its own antibodies
all three polio virus types recognized at the time
T:at the time