Vaccination regimes
1 Kittens born to mothers with moderate titres acquired through vaccination.
Lose their maternally derived immunity at 8-12 weeks. (a) Vaccinate at 12 weeks if little risk of exposure and can keep isolated until vacc. Immunity develops.
(b) Vaccinate at 8-9 weeks if exposure likely, with second dose 3-4 weeks later.
2 Kittens born to mothers with high titres as a result of exposure to virulent virus or vaccinated with live virus just before or during pregnancy.
Maternally derived immunity may persist for 16 weeks. As above but extra dose at 16 weeks plus.
3 Kittens presented at 12 weeks of age with unknown vaccination status.  
  Generally one dose sufficient but additional dose at 16 weeks if category (2) suspected.

4 Kittens born to mothers where inadequate maternally derived antibody suspected and exposure likely.
  Vaccinate at 4-6 (inactivated vaccine), 8 and 12 weeks of age.