Vaccinations – What is all the fuss about?
by Liesel van der Merwe
I am going to try and demystify the whole vaccination process for all you pet owners out there. This will involve me taking some liberties with the exact detail of the immunological process, so to those with a bit more knowledge on the subject, please bear with me.
Antibodies are the “tracker system” of the body. They are a type of protein which is designed to identify only a specific foreign substances (viruses, bacteria, protein particles in allergies). Each pathogen thus has a specific antibody. One they have identified an “intruder” they attach to it and flag it for the immune system cells. These cells then engulf the foreign substance and process it to activate the immune system. Young animals are not born with their own antibodies, these only develop with time due to exposure to the environment and pathogens.
In humans, the placenta allows mixing of maternal and foetal blood and a baby is born with its mothers antibodies in the blood to ensure early protection. The placenta in animals is not as intimate and blood is not shared. Young animals rely on antibodies which have accumulated in the first milk (colostrum). Milk contains high levels of antibodies throughout lactation in cats, but antibody levels drop rapidly in other species. The stomach is normally impermeable to proteins and the acid would normally digest proteins but in the first 12-24 hours after birth there are gaps in the stomach lining allowing antibodies to be absorbed into the bloodstream of the newborn, these then provide protection in the first 6 weeks of life. It is thus vital that newborn animals suckle within the first 12-24 hour of life.
All proteins in the body have a lifespan and are recycled, and these antibodies start decreasing so that at about 6 weeks they are no longer very protective. This is when vaccination plays a role. Vaccinations are either a “dead” form of the virus or bacteria, a modified live or weakened form or a reconstituted vaccine which uses only a part of the virus. Vaccination hardly ever cause disease in dogs and cats although they can in animals such as the wild dog , panda and other wild canidae and felidae. The first vaccine can only be given once the maternal antibodies are decreasing , otherwise they will identify and block the immune response, this is why we generally give the first vaccination at 6 weeks. If there is a problem with a disease in a kennel , we can start at 4 -5 weeks.
This first vaccine primes the body against the disease. The body has to identify the pathogen as foreign, without the benefit of antibodies, as they are not yet present, and present it to the cells of the immune system which will make specific antibodies , and make memory cells against that specific pathogen. This whole process takes about 3 weeks and is called seroconversion. The reason for the booster 4 weeks after the first vaccination and again 4 weeks later is to remind the immune system and thus really establish a good memory. In some cases it can also be argued that the maternal antibodies may have still interfered with the 6 week vaccination, so we are really trying to cover all bases. The rabies vaccination is usually delayed until after 3 months as maternal antibodies interfere with the vaccination if the puppy is younger.
The booster at 1 year is important to set the memory as well as boost the rabies vaccination. The duration of the immunity or memory of the body is different for different organisms. That developed against rabies is long lasting and that against snuffles or kennel cough has a shorter duration. Thus each individual animal has a different antibody profile depending on their exact environment and vaccination status.
The response of a vaccinated animal to a virus is much quicker as the virus is identified earlier and memory exists, this antibodies are quickly made as the “recipe “ is already known, whereas in an unvaccinated animal the immune system first has to identify the virus without the help of antibodies, break the virus into bits to find the the recipe required to identify it again and then programme cells to make this antibody. This time lag will allow the infection to become established in the body.
Vaccinated dogs are primed to identify and destroy, thus preventing establishment of infection.
Vaccinations do not work very well in dogs which are malnourished and in animals with a compromised immune system and drugs such as chemotherapy and cortisone will also reduce efficacy.