Vaccine is a general term of all antigen preparations for infectious disease prevention.
In a broad sense, vaccine includes bacterin and vaccine; in narrow sense, vaccine merely refer to the biological products derived from virus, rickettsia, spirochete and other microbes. Common vaccine can be divided into live vaccine and dead vaccine.
1. Bacterin: on the bases of the way of processing the antigen strains, bacterin can be divided into dead bacterin and live bacterin. Dead bacterin is a virulent strains which have a good immunogenicity .It is generated by growing and reproducing in an appropriate medium, being inactivated in the basis of the integrity of its antigenicity. The advantage is that they are stable, safe, and can be saved in a year or so. But its immunity is lower than live bacterin. It has a large immunization times and cow, while a slow speed to immune and a short time to maintain the immunity.
To compensate, adsorbent such as aluminium hydroxide is added to some bacterin to enhance the intensity of stimulation. Repeated injection can also make the body gain a robust and durable immulity. The common dead bacterin include Cattle hemorrhagic septicaemia aluminum hydroxide vaccine, sheep colibacillosis inactivated vaccine, gangrene emphysematosa alum vaccine. The live vaccine is generated by cultivating and reproducing the strains with hypovirulence and high immunogenicity. When live bacterin enter the body, it can continue to reproduce, stimulate the body for a long term, and continue to produce antibodies. Compared with dead bacterin, live bacterin have some advantages such as low inoculum size, a few vaccination times, remarkable immune effect, and long immunity period. The common live bacterin include swine plague attenuated vaccine, avian cholera attenuated vaccine, anthrax spore vaccine Ⅱ,, etc.
2. Vaccine: utilizing virus or rickettsia to inoculate animals, chick embryo and cultring the tissue before the further processing can produce a vaccine. Vaccines can also be devided into attenuated vaccine and inactivated vaccine after injecting an attenuated vaccine into an animal, there is little symptom on it. If there is a symptom, it is very tiny. Other advantages just like live bacterins. But if the storage tempreture is not appropriate, it is easy to lose efficacy. So the vaccines are often lyophilized, and equipped with appropriate refrigeration equipment. the can common attenuated vaccine include rabbit adapted hog cholera attenuated virus, newcastle disease strain attenuated vaccineⅠ, newcastle disease strain attenuated vaccine Ⅱ, etc. inactivated vaccine is produced by inactivating virus while protecing its immunogenicity, such as goat pox aluminum hydroxide vaccines.
3. Toxoid: toxoid such as tetanus toxoid is a nontoxic preparation of immunogenicity, which is derived from the exotoxin of bacteria after added with formaldehyde.
