De or het vaccinering?

The correct Dutch article is:

de vaccinering

Rule Words ending in -ing: almost always de. See the rule

How to use vaccinering

the vaccineringde vaccinering
this vaccineringdeze vaccinering
that vaccineringdie vaccinering
our vaccineringonze vaccinering
your vaccineringjouw vaccinering
every vaccineringelke vaccinering
which vaccinering?welke vaccinering?
a big vaccinering / the big vaccineringeen grote vaccinering, de grote vaccinering