Feline coronavirus (FCoV) does not cross the placenta to the unborn kitten. Kittens are born FCoV free and are protected from FCoV infection by antibodies they receive in their mother’s milk. When these antibodies wane at around 5-7 weeks of age, the kittens become susceptible to FCoV infection and the attendant risk of FIP.
FCoV prevention in kittens is commonly known as the “early weaning and isolation” technique and has enabled cat breeders to continue to breed from queens who are actively infected with FCoV and shedding the virus.

Protocol for prevention of FCoV infection in kittens:

Prepare kitten pens
Disinfect pens between occupants using 1:32 dilution of sodium hypochlorite (household bleach) and vacuum diligently removing any microscopic dust-sized particles of infected cat litter.
Introduce queen to this room 1-2 weeks before she is due to give birth (make sure all other cats stay away from this room).
Color code and dedicate litter trays, food and water bowls to kitten section and frequently disinfect with sodium hypochlorite (1:32 water dilution – meaning 1 cup of bleach and 31 cups of water) please make sure to rinse dishes thoroughly in hot water upon disinfecting.
Allow expectant queen to get used and relaxed in the kittening room, if needed use a cat hormone diffuser (i.e., Feliway®).
Provide nice, clean, newly wash bedding avoiding any type of chemical smells.
Practice barrier nursing.
Deal with the kitten section of the cattery before tending other cats, meaning, deal with the least infected area of the cattery – in this case, the kittens’ room – and gradually move up to the most infected area (i.e., known FCoV shedding cats).
Clean hands with disinfectant before going into kitten section.
Have shoes and coveralls (clothes) dedicated to the kitten section.
Very large breeding catteries should have disinfectant foot baths between each major area.

Early weaning and isolation of kitten.
Test queen for FCoV antibodies either before or after kittening.
If queen’s antibodies titer is greater than zero, the kittens should be removed to another clean pen when they are 5-6 weeks old or at least keep the queen’s litter tray out of the kittens’ reach.
If the queen has an antibody titer of zero (FCoV free), she can remain with the kittens until they are older.
Keep kittens isolated from any other FCoV infected cat(s) in the cattery.

Knowing the FCoV antibody titer and virus shedding status
of your breeding queen is absolutely essential.

Test kittens
At ten weeks of age, test kittens for FCoV antibodies.
Kittens who have FCoV antibody titer of zero by a good, sensitive, antibody test are safe to sell and re-home.
Kittens who have an antibody titer greater than zero should be further isolated and re-tested four weeks later. Consider sending fecal samples for FCoV RT-PCR to find out if they are actively infected and shedding virus.