By: Dr. Nuzhat Hassan
The vaccine is an antigen derived from infectious agents and vaccination is the administration of the vaccine to an animal so that the specific immune response is mounted and the animal becomes resistant to infection. Vaccination is one of the most important measures to prevent infectious diseases. The aim of the vaccination is to prevent disease occurrence rather than to prevent clinical signs of the disease. There are numerous advantages of vaccination as it prevents disease occurrence that can sometimes result in mass culling or death of the animal population. Veterinary vaccines have dramatically enhanced animal health and efficacy of food production. Due to recent advances in research in this particular field, vaccines are much more effective and safer now. Vaccination of a large proportion of farm animals can lead to the protection of the entire herd due to a herd effect that slows down the circulation of a pathogen in the immunized population. There are even vaccine failures which may be due to problems with either owner’s education or compromise with good animal management practices. It is important for the animal owner to understand the proper timing and method of vaccine administration, what is extremely important for vaccine efficacy and an augmentative step in minimizing immunosuppressive factors and exposure to high doses of infectious agents in vaccinated animals. It is important to note that a safe vaccine is not simply one that has been manufactured, tested and found to be safe in clinical trials. There are other points that make immunization safer which include safe transport of the vaccine, safe administration, safe disposal of the vial and injection equipment. It also includes post vaccination surveillance to detect desirable outcome. Also veterinary vaccines whether attenuated /live or non-infectious from the different manufacturers can vary in their potency, efficacy, and duration of immunity. Attenuated vaccines tend to induce stronger and long-lasting immunity than the non-infectious vaccine. Non-infectious vaccines which include killed, toxoid, subunit, and DNA vaccines are safer and more stable than attenuated or live vaccines. But the decision of using Live or non-infectious vaccine depends on the risk factor and immune status of the animal. It is generally recommended that booster doses of vaccine should be given following a primary course. For effective vaccination, an animal must have an effective immune system in order to respond appropriately to a vaccine.
The key points to be kept in mind for vaccination are:
Age of the animal may affect vaccine responses as it has been found in some studies that older animals had lower titers after vaccination.
There are host factors affecting vaccine efficacy that are to be conceived as all animal do not respond equally well to vaccination and even some may not present an effective immune response. One of the important factors is maternal antibodies that can interfere with the ability of vaccines to induce immunity. Maternal immunoglobulins are acquired by newborn from the mother and circulate in the newborn’s blood for a number of weeks that may be different in different gestation periods and between animals. This is the period in which the maternal antibodies are too high to provide protection against disease, but at this time period, vaccines are ineffective to work.
Every infectious disease has an incubation period before any clinical signs of disease become apparent. The duration of the incubation period varies from a few hours, few days or as long as a few years. Now here the point is that if an animal is incubating infectious diseases at the time of vaccination or has some concurrent infection then it may develop clinical signs with an equal chance of vaccination failure at that stage.
Managemental practices that expose animals to severe stress following vaccination and poor feeding can suppress immune responses by decreasing nutrient availability for cell division and may result in an inadequate immune response.
Incorrect handling or storage of the vaccine, resulting in an in-effective vaccine being administered will not provide protection. There are several factors within the control of the vaccinator or farmer that may affect vaccine efficacy. First, vaccines should be stored at the appropriate temperature recommended by the manufacturer and this is especially applicable to live vaccines which might be inactivated at higher temperatures. Keep vaccine container in ice-bath and don’t expose to sunlight.
Manufacturer’s instructions should be strictly followed. Each vaccine has an expiry date printed on the vial which one should strictly adhere. Vaccines that are to be reconstituted with the supplied diluents should be used immediately.
Similarly, vaccines are developed to be given by a certain route, either intranasal, subcutaneously or intramuscularly. If a vaccine is administrated by a route different from the route for which it was developed, it may not be effective and could cause considerable harm.
During transport and storage vaccines must be maintained at the correct cool or cold temperature as well as after reconstitution and during use.
Also, the owner should bear that a vaccine does not immediately provide protection. It takes from days to a week or more for an animal’s body to respond to the vaccine. For some vaccines, an adequate level of immunity usually does not occur until a few weeks after the second vaccination in the series.
In J& K state, large animals are to be vaccinated against various endemic and infectious diseases occurring commonly. Following are the diseases against which vaccination may be done.
Haemorrhagic Septicemia, Black Quarter, Brucellosis, Enterotoxemia, Anthrax, Tetanus, Mastitis.
Foot and Mouth disease, Rabies, Sheep pox, Peste des Petites Ruminants, Footrot
Against these diseases various types of vaccines are available and timely vaccination with reliable vaccines is very essential.
Although vaccination programme may be adequate to control infectious disease under normal condition of exposure, it should be remembered that they may not protect under the severe condition of a challenge. Veterinary vaccines not only protect animal health but also human health. Vaccines are environmentally safe, enhance the longevity, the productivity of animal thereby decreasing the use of antibiotics that further result in antibiotic resistance otherwise used to cure the disease. In nutshell, following the instructions are properly given with the vaccine vial, safe transport and administration, screening the animal’s post vaccination and reporting of any vaccination failure will definitely help the animal owner to achieve the maximum benefit of vaccination.
(The writer is Jr. Scientist SKUAST-Kashmir)