Posted by on 18. March 2021

For a given occasion, I would like to comment here from an immunological point of view on the pros and cons of herpes vaccination.

For which diseases do vaccinations really make sense?

Basically, vaccinations only make sense if a disease is also mainly fought via antibodies.

Many respiratory diseases are not or marginally controlled by the humoral system (i.e., antibody-dependent) or are controlled only in exceptional cases and at a late stage. This is because these viruses are mainly located on the mucous membranes and the mucosal surface does not have a good connection to the vascular system.
These respiratory infections must be defeated and fought before they penetrate the deeper layers of the tissue. So also before they have contact with the blood vascular system and antibodies (IgM and IgG).

This happens mostly via the local defense of resident immune cells, T cells and macrophages and the old, non-specific part of the immune system. But also via the mucosa-bound antibodies, the IgA.

Another reason why certain viruses are not fought via the humoral system is that these viruses are not stable enough. That is, they change their surface antigens and protein structures very often. Vaccines, which take several years to develop, are not very effective when they are finally used. The same would happen to the antibodies formed in the body. Hardly formed they are also already outdated and the body possesses a plasma cell, 12 to 20 years surviving, which has no more effect at all. Thus every half year… that would be very ineffective.
Thankfully, our immune system is smarter.

The nonspecific immune system


Toll-like receptors are used to recognize such viruses. These receptors recognize general structures that are common to all viruses and bacteria, no matter what disease they cause.
And, as mentioned above, defense occurs via local, resident, and cellular defenses.

This is why herpes and influenza vaccines have a very poor response. Meaning: even if horses are vaccinated religiously every six months, good antibody titers are very rarely detected. And, as insane as it sounds, in some cases this is a good thing.

As an example: the viral abortion in mares triggered by EHV-1
Studies have shown that mares with a very high titer of EHV-1 antibodies abort most often. Mares without antibodies almost never abort.

Because herpes is not that simple. It is not black or white, herpes or no herpes.
It is believed that 90% of our horse population is already infected with herpes. This is because the herpes virus has the ability to mask itself in our body cells from our immune system. Our immune system tolerates the invader, it does not fight it until a trigger is added or the virus is released from the cells of the body.
This happens primarily when it enters a multiplication phase during an outbreak.

What does the herpes vaccination really do?

flu horse

It reduces the mild course of EHV4. The course that causes fever and in some cases – but not always – cough.
In contrast, vaccination is almost completely ineffective in the EHM course and, as described above, almost beneficial in the viral abort.
Incidentally, this is also confirmed by Prof. Feige of the Permanent Vaccination Commission Veterinary and Prof. Thein in their interview with Cavallo.

Does herpes vaccination make sense at this point in time?

A clear no.

Not only because you generally don’t vaccinate into a herd with high infection pressure. There are probably a great many horses that are just quietly dealing with the herpes virus without many symptoms.
Vaccinations always weaken the current defenses and therefore should only be given at times of low infection pressure.

And something to think about. The horses that are right now dying from EHM are FEI show horses that have been constantly vaccinated every six months. Obviously, the vaccination did not help them at all.

The magic formula is called:

    1. strengthen the immune system. Because a healthy, powerful immune system is the best protection against viruses. Here, too, there are wonderful approaches in phytotherapy.


    2. limit contacts with horses not in the stable, avoid large tournaments and act hygienically responsible. This applies forever, not just during a herpes outbreak. These things are stressful for horses, even though we often tell ourselves otherwise


It makes no sense, while there is just an infection pressure, to scream panic for the vaccination to prevent the EHM. Vaccination is not capable of doing this.

It also makes no sense to quickly vaccinate allergic horses or horses that have already reacted badly to the vaccination. As some studies show, vaccination has the potential to aggravate the allergy.
And as I can say from personal experience from 2 weeks ago: Yes, horses do die from herpes vaccination if they have previously shown signs of intolerance. Even young horses.

It makes even less sense to vaccinate mares against herpes during pregnancy. Good hygiene management to separate infected mares from young mares would be much more effective.

Of course, everyone is free to vaccinate his horse against herpes if he wants to.

Everybody has got the right to build his opinion based on the information given to him.
What I would like to point out, however, is this:
The animal immune system is almost exactly the same as the human immune system.

Does influenza vaccination prevent the severe course in humans? No.

Do we get vaccinated against everything every six months? No.

And why not. Because vaccines, if they do induce immunity, cause the formation of memory cells that have a lifespan of 12-20 years. This means that if a vaccine is capable of inducing an antibody response, I don’t need to vaccinate again until the memory cells have died.

If a vaccine is not capable of triggering an antibody response I don’t have to vaccinate it. Because then our body has other ways to cope and doesn’t need the constant burden of a bi-annual vaccination that does nothing to an antibody response.