The vaccine used should contain virus strains which will protect against those types of virus known to be present in the area.
(The vaccine used; should contain; virus strains which will protect against those types of virus) (virus strains; will protect; against those types of virus) (those types of virus; known; to be present in the area) (those types of virus; to be; present in the area)
The vaccine used virus strains those types of virus those types of virus
should contain will protect known to be
virus strains which will protect against those types of virus
against those types of virus
to be present in the area
present in the area