vaccination

[linga]

Ok, I know the proper answer to this but here goes anyway.
With vaccinations that require 2 doses, I always think the first dose primes the immune system and the second activates / tests the system.
Now if an animal has the first dose and the second dose is neglected would it not be true that if the animal comes into contact with the virus in the environment that would take the place of the second dose and the animal would achieve immunity?
So whilst I can see that the two dose system would be ideal would a single dose and rely on environmental dosage achieve an appreciable level of immunity?
If you see what I mean !

 

[Thick Farmer]

I have only ever given one dose of blackleg vaccine, but recently found out that others give two.

Haven't had anything die of blackleg since giving the one dose.

 

[linga]

Anyone else anything to add ?!!

 

[Global ovine]

Two different responses occur with those vaccines which REQUIRE a second shot. The first activates the Igg response......recognition of the particular new protien you have introduced, some build up of immune response occurs (thats the host body's antibody mechanism). The second shot activates the second response (the IgM) which is the body recognising that more of that protien has entered and now it has the tool to fight it, it produces large amounts of antibody which last for some time to prevent the foreigner from becoming established if it does infact invade.
The 2nd shot should be between 3-6 weeks after the first to give maximum protection. Therefore the timing of the first shot should be about a month before a particular disease usually occurs on that farm.
The protien may be killed pathgen protein, or just the protein from the outside of the pathogen which the host body first recognises, etc.

By only giving one of the two shots severely compromises the animal's ability to fight the establishment of an attacking pathgen, hence the disease may establish.

No vaccine is a 100% guarantee of giving total immunity. All of nature is varying shades of grey, rather than black and white.

 

[EJS]

GO is right, a vaccine requiring a second shot should be given it, the second does ensures that the animal can mount an immediate immune response to the disease should it be encountered, however there are several different types of vaccine which initiate the adaptive system in different ways, I would definitely follow the instructions in the packaging.

 

[linga]

Yes, I can see that is the correct answer but coming into contact with the pathogen in the environment after the first dose will have the same effect as the second dose wont it ? ie. it will provoke an immune response to the challenge.
I accept that there is a risk that the pathogen may overwhelm the immune system at this stage but it may not of course. All these pathogens are in the environment anyway so the animal is being challenged all the time, vaccine or not.
Under these circumstances the animal may already have produced an antibody response similar to that of the second dose might it not ?
I am not advocating ignoring the instructions just musing.

 

[EJS]

I think you are right, if the animal is exposed to the actual pathogen after only having a primary dose, it can act as a booster, assuming it is a low level infection, but that is dependent on the type and nature of the pathogen you are trying to vaccinate against. The ideal is to have an army of memory cells already primed to defend against that particular pathogen immediately it sees it in the disease form, which generally comes from having had more than one exposure to 'safe' pathogen in the form of a vaccine. The risk of leaving the booster effect for the disease pathogen to do itself, is that the animal is overcome by disease before the immune response has developed sufficiently to fight it off. Interesting subject though, I am sure there are vaccines for which a primary dose only would work. Have always wondered about tetanus, as humans used to have it every 10 years but horses were advised to have it every year - I would imagine there would certainly be some leeway there.

 

[Y Fan Wen]

IME you certainly increase the resistance after 1 shot, get fewer falling over in other words. When I was feeding off ram lambs on forage crops I would only give one shot. Dad also gave one shot to the kept ewe lambs but I wasn't satisfied with the mortality, so changed to 2 shots, which I don't regret having done so.
A vet did comment that he thought, from the ewe's point of view, that 3 shots would protect for life and that the booster was for the unborn lamb.
After Dad died, I started injecting the ewe lambs earlier, the first when weaning the ram lambs, and the second when selecting the draft ewes and got a drop in mortality.
This is in the context of a mountain flock where gathering is a serious operation.

 

[Ysgythan]

Ok, I know the proper answer to this but here goes anyway.
With vaccinations that require 2 doses, I always think the first dose primes the immune system and the second activates / tests the system.
Now if an animal has the first dose and the second dose is neglected would it not be true that if the animal comes into contact with the virus in the environment that would take the place of the second dose and the animal would achieve immunity?
So whilst I can see that the two dose system would be ideal would a single dose and rely on environmental dosage achieve an appreciable level of immunity?
If you see what I mean !

the first dose gives you a brief window of cover, the second extends that window substantially. Giving only the first wastes more money than not giving the second saves.