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Understanding vaccinations, serology, and the immune system

Updated: Oct 19, 2019

In today’s society, more and more people own companion pets. With keeping pets comes the responsibility of keeping them healthy; to do this a good knowledge of what medical care is available is needed. Veterinary care is one of the most important aspects involved with keeping a pet healthy and there are many vital treatments which vary depending on species and age.

Vaccinations and preventative treatments are highly recommended to pet owns with puppies and kittens to give them the best start in life, and there are booster vaccinations available to older animals to continue their good health and strong immune systems. Knowing the vaccination protocols for certain species, an understanding of why vaccinations are used and how they work, knowledge of how serology can be used to help the immune system and how immune response differs depending on the type of illness in an animal will help both veterinarians and pet owners care for their pets.

Vaccination Protocols

For a puppy aged 6 weeks old to a dog aged 5 years.

Preventative veterinary care involves vaccinating a puppy or dog against common or dangerous diseases and illness. There are a range of diseases that are vaccinated against, some viral and some bacterial. There are different types of vaccination which protect the body in different ways. These can be either modified live virus (MLV) for viral diseases or ‘killed’ vaccines for bacterial diseases. The MLV vaccines are as the name suggests, live, and will grow within the dogs body to activate and immune response. They do not however, cause clinical signs of the disease in healthy dogs. Killed vaccines are used to stimulate a weak immune response, as they do not reproduce in the body like the MLV. They do not usually protect as long as the MLV vaccines (Carricato, 1992).

Vaccination Protocol

The vast majority of vet practises vaccinate at 6, 9 and twelve weeks old. They then need to be given a booster vaccination; usually annually (Carricato, 1992). The diseases which are routinely vaccinated against are Canine Distemper, Canine Parvovirus, infectious hepatitis, Canine Tracheobronchitis (Kennel Cough) and leptospirosis (Weil’s disease) (Turner, 1998). The table below outlines the protocol for vaccinating dogs.

Age; Vaccination; Reason 6 weeks Combination; Hepatitis (adenovirus), distemper, parainfluenza and parvovirus. The passive immunity that the puppy has received from its mother begins to wear off between 6 and 16 weeks, so it is important to vaccinate sooner rather than later. As there is a chance the passive immunity could wear off, vaccines need to be administered as early as possible (Tizard, 2009)

9 weeks Second combination vaccination with leptospirosis and kennel cough (bordetella). Repeat vaccinations are necessary for neonatal animals as their immune systems work differently at a very young age. The passive immunity from the mother’s colostrum will prevent the vaccine working. As there is no telling when passive immunity wears off, repeat vaccines are given at these intervals to ensure at some point the vaccine will work (Day, 2011).12 WeeksThird combination vaccine.

16 weeks Rabies This is the date when a dog can be vaccinated against rabies (if it will travel abroad). This is not part of the regular protocol as the UK has a ‘rabies-free’ status (Defra.gov.uk, 2011)

1 year Booster Vaccination Annual boosters are required to re-produce antigens for protection against deadly diseases. These boosters are given annually to be sure that the vaccinations do not wear off. If left for more than a year, the dog may be vulnerable to some of the diseases. (Day, 2011)

Continue each year.

Why this protocol has evolved

The vaccination protocol that is familiar in all veterinary practices has been put in place for various reasons. The reasoning for why puppies are vaccinated at particular ages has been discussed, however there are good reasons why these specific diseases are vaccinated against. There are two main factors contributing to the diseases which are vaccinated against; the seriousness of the diseases and how common and contagious the disease is. Distemper, for example, is fatal to almost all puppies and dogs which catch it. Although it is not particularly common, the consequence of catching the disease is almost always life threatening. Parvovirus is both quite common and can be fatal to puppies which catch it. Bacterial Kennel Cough (Bordetella) is almost never life threatening but it is however highly contagious and commonly seen. Due to is being so contagious, it is routinely vaccinated against (Carricato, 1992).


Serology is the study of the interaction between antigens and antibodies found in blood serum (Jackson and Jackson, 2008). Serology is used to investigate disease and infection by measuring the presence of a specific antigen for diagnostic purposes. There are many things a veterinarian can tell from serological testing, including whether an animal is infected with a disease, if the disease is getting worse or getting better, and whether a vaccination has worked properly. When doing a serological test, the presence of antigens will tell you that the animal is infected. If another test is taken a week later, the levels of antigen will tell the veterinarian whether the disease is getting better or worse. Initially, the presence of a specific antigen will tell the vet whether the animal is infected, or if the body has responded to a vaccination. The measurement of the concentrations of antibodies in the serum is called the titre. (Day, 2011).

The Pet Passport Scheme

The pet travel scheme (PETS) is the system used in the United Kingdon to allow the movement of dogs, cats and ferrets in and out of the UK without having to go into quarantine for six months. The system was set up to protect the UK and it’s rabies free status. To have a pet moves under the PETS scheme, they must first be micro-chipped and vaccinated against rabies. It is then vital to have the animal’s blood tested to prove the vaccination has worked. This is done using a serological test (defra.gov.uk, 2011). The pet will be vaccinated against rabies which will trigger the immune system to produce antibodies which fight rabies. The serological test is then done on the animal’s antiserum; the serum from an animal which has been exposed to an antigen to get an immunoglobulin response. If there are enough of the antibodies in the serum test, the pet is classed as vaccinated against rabies (Day, 2011). The test must produce a titre that is equal to or greater than 0.5 IU/ml to show positive protection (defra. gov.uk, 2011).

Using serology with routine vaccinations

Serological testing is used in the pet passport scheme as a way of ensuring it has worked. In comparison, routine vaccinations for preventable diseases are given a number of times including an annual booster to ensure the animal remains protected. Although boosters are given annually, some of the vaccinations last for much longer; MLV can last from a year to a life time.

One study shows that even identical vaccinations can vary in duration depending on the individual animal. If serological testing were to be introduced as part of routine vaccinating, it may allow fewer vaccines per animal and also allow the vet to be more accurate to when an animal will need vaccinating. This however poses a few risks; some animals may not be protected if the vaccination wears off sooner rather than later and serological tests require specialist equipment and can be very expensive (Burr, 2006).

An understanding of immunity is important to both pet owners and veterinarians, as it allows them to keep domestic animals as healthy as possible. The correct vaccination protocol will allow a pet owner to protect their animal from some of the most dangerous viruses in the environment of the United Kingdom. Finally, understanding serology will allow us to continue to keep the UK rabies free, and demonstrate the importance of the pet passport scheme and protecting the boarders to the general public.

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Department for Environment, Food and Rural Affairs. http://www.defra.gov.uk/foodfarm/farmanimal/diseases/atoz/rabies/ 13th March 2011

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