Vaccines: comprehensive preventative health care series

Regular assessment of vaccination needs is just one component of a comprehensive lifetime health care plan. Individualised patient care requires regular (usually annual) health checks, with the preventative health care plan designed around the age, breed, lifestyle, environment and travel activities of the pet and owner. Discussion of vaccination is one important part of such a visit, alongside consideration of ecto- and endoparasite detection, treatment and prevention, vector-borne and zoonotic disease prevention, dental care, nutritional advice, behavioural assessment and advice, and the necessity for any more frequent, tailored examinations of the pet.

Studies of UK dogs and cats vaccinated for the first time against rabies for pet travel have shown clearly that many aged animals fail to achieve the legally required antibody titre (Kennedy et al., 2007; Mansfield et al., 2004). Younger animals were more likely to be successfully immunised.

Effects of maternally derived antibodies on immunisation

In most puppies and kittens, MDA (maternally derived antibody) declines to levels that allow an active immune response to vaccination by about 8 to 12 weeks of age. Puppies with low amounts of MDA may be vulnerable (and capable of responding to vaccination) at an earlier age, while others may possess MDA at such high levels that they are incapable of responding to vaccination until ≥12weeks of age (Friedrich & Truyen, 2000; Thibault et al., 2016).

FIG 1. How maternally derived antibody (MDA) interferes with a veterinarian’s ability to immunise puppies or kittens through early vaccination. This graph shows a puppy’s serum antibody (Ab) concentration or “titre” on the vertical axis and age in weeks on the horizontal axis. The antibody shown happens to be against canine parvovirus, but the same principles apply in both puppies and kittens to a variety of pathogenic agents. Shortly after birth, this puppy acquired a substantial amount of anti-parvoviral antibody from its mother, via colostrum. This is the so-called “maternally derived antibody” or MDA (the red line). MDA declines exponentially with a half-life of approximately 9 to 10 days. The syringe icons represent repeated vaccinations, the first of which was given at 6 weeks of age. This first vaccination did not immunise the puppy because of interfering MDA, which neutralised the vaccine. The same is true of the next two vaccinations. At 8 weeks of age, this puppy became susceptible to parvoviral enteritis, because its MDA concentration fell below the level required to protect from a moderate challenge with canine parvovirus. Yet it could not be immunised at that age, because the level of MDA was still sufficient to interfere with the vaccine and to prevent active immunisation. By approximately 13.5 weeks of age, the level of MDA in this puppy fell low enough to permit immunisation. At 16 weeks of age, the puppy was revaccinated and promptly made its own active immune response (the blue curved line). The pink-shaded rectangle between dotted lines represents the “window (or period) of susceptibility” for this puppy, during which it was susceptible to parvoviral disease. It is not recommended to routinely measure MDA in very young puppies. Some puppies might receive more or much less than did this puppy. So this is why repeated vaccinations are given every 2 to 4 weeks, to narrow the “window of susceptibility” for puppies and kittens as much as practicable. Ab Antibody, MDA Maternally derived antibody; syringe icon, vaccination.

Core vaccines for pet dogs

Core vaccines for dogs that are relevant throughout the world protect against disease caused by canine distemper virus (CDV), canine adenovirus (CAV) and canine parvovirus type 2 (CPV). In addition, veterinarians working in certain places designate other vaccines as core, for example those that protect against rabies and leptospirosis. Wherever rabies is endemic, all dogs and cats should be vaccinated for the protection of both pets and humans even if legislation does not require this. Mass canine vaccination has been shown to greatly reduce or eliminate rabies cases (Zimmer et al., 2018). 

The Vaccination Guidelines Group (VGG) recommends initial vaccination of puppies against canine distemper virus (CDV), canine adenovirus (CAV) and canine parvovirus type 2 (CPV) at 6 to 8 weeks of age, then every 2 to 4 weeks until 16 weeks of age or older. The more frequently these vaccinations are given, the narrower (or shorter) will be the “window of susceptibility” for the puppy. Vaccinating more frequently than every 2 weeks is not advised. It follows that the number of these primary core vaccinations will vary somewhat and will depend on the age at which vaccination is started and the chosen intervals between vaccinations. The most important of these early vaccine doses is the one administered at 16 weeks of age or older. 

Core vaccines for pet cats

The core vaccines for cats relevant in all parts of the world are those that protect against feline panleukopenia virus (FPV), feline herpesvirus (FHV) and feline calicivirus (FCV). The VGG recommends an initial trivalent kitten core vaccine at 6 to 8 weeks of age, then every 2 to 4 weeks until 16 weeks of age or older, with a subsequent dose given  at 6.5 months of age or older, by which time MDA is likely to have waned sufficiently so that all kittens can respond to vaccination.

Rabies vaccination schedule depends on locations which more exposure to rabies:

Follow any local laws or regulations as a priority. Follow the product leaflets of locally manufactured vaccines. In some countries, the first dose is generally not given before 12 weeks of age.

References & further reading:

Squires, R. A., Crawford, C., Marcondes, M., & Whitley, N. (2024). 2024 guidelines for the vaccination of dogs and cats – compiled by the Vaccination Guidelines Group (VGG) of the World Small Animal Veterinary Association (WSAVA).