Besides giving OPV viruses more time to die out before there are large numbers of non-vaccinated people, the use of inactivated vaccine after OPV vaccination stops would also make monitoring for polio virus easier.
(OPV viruses; to die out; T:more time) (the use of inactivated vaccine; would make; monitoring for polio virus easier; T:after OPV vaccination stops)
OPV viruses the use of inactivated vaccine
to die out would make
T:more time
monitoring for polio virus easier T:after OPV vaccination stops