Summary
There are two ways that kittens acquire antibodies against diseases; one is active immunity and the other is passive immunity. Understanding the processes of acquiring immunity is an important concept that will help promote the health of kittens under your care.
Passive and Active Immunity in Kittens
Passive Immunity
Passive Immunity is defined as the transfer of antibodies from one individual to another, in this case from queen to kitten. A kitten can receive maternal antibodies from the queen in two ways: through the placenta while still in utero or the colostrum, a queen’s first milk. In kittens, colostrum acquired while nursing from their mother during the first 24 hours of life is considered the main source of passive immunity and contains antibodies that provide immediate but short-lived protection.
It is essential that newborn kittens have a chance to suckle from their mother immediately following birth to receive this essential colostrum. While other colostrum supplements may provide some immunity, every effort should be made to allow kittens to receive the natural colostrum from the queen following birth. Passive immunity may also be achieved via subcutaneous injection of serum from a healthy donor cat.
Active Immunity
Active Immunity results from antibody production in response to an antigen or pathogen. A kitten can produce an active immune response from a natural infection or a vaccination. Proper vaccination is critical for preventing the spread of disease between cats and kittens as well as between cats and humans (i.e., rabies).
Our intent here is not to provide exact recommendations for when to initiate vaccination series in kittens, as this should be a discussion between you and a veterinarian. That being said, in 2020 the American Animal Hospital Association and FelineVMA (formerly the American Association of Feline Practitioners) created a comprehensive Vaccine Guideline document that can be referenced for more information.
