Pigeon health

   medication - vaccination

26.11.2007.
Dr. Botond Siklodi, my friend and colleague, editor of my first pigeon book, had written a long, detailed and very useful article about medication and vaccination.
The article is a little long, indeed, but it is worthy to read. (even two times)

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         Basic principles in pigeon medication with special focus on vaccination
   by Botond Siklodi, DVM, editor of the book Pigeons and their Economical Health Care

Overmedication of racing pigeons is a serious mistake by many fanciers today. Fortunately, veterinarians, pigeon breeders and top racers who recognized the danger started an educational campaign explaining the damages that overmedication can cause to the birds. This is a really good thing, and sooner or later, the joint efforts of these experts will hopefully stop the negative trend of antibiotic abuse.
However, experience shows that a campaign that aims to stop a negative trend sometimes results in an opposite trend that will eventually swing back too far to the other extreme point which is not necessarily better than the previous one… What would be the other extreme in pigeon health care that we should avoid? The opposite of too much medication is no medication at all. It would probably cause as much damage to pigeons or even more than overmedication. Strike a happy medium. This is what I always try to follow because I am sure that the truth is always in the middle between two extremes.
Do not through the baby out with the bath! Medication itself is not evil. Only inappropriate medication is. In other words, if medication is evil then, it is a necessary evil. We cannot avoid it completely but we should try to minimize it to the absolutely necessary level.
So, the ultimate question is this: What is the absolutely necessary level of medication in pigeon care? Of course, this is a very complex question, and veterinarians have to study hard for many years to gain sufficient knowledge and experience to be able to answer this question. There is no general magic formula that works equally well for everyone. The circumstances might be profoundly different in Canada than in Florida. But there are general rules and principles that every fancier could and SHOULD learn and understand because these principles remain the same under all circumstances. If you know these principles and correctly apply them to your local circumstances, you will be a WINNER.
As Dr. Talaber writes in his book, Pigeons and their Economical Health Care:
“We must be aware of why we do what we do, we must know the principles and how they relate to practice, for this is how we can make progress, and think in terms of our flock.”
I would highly recommend this book to every fancier because, in a systematic manner, Dr. Talaber explains the most important principles in a plain language that everybody can understand. Once you have learned these basic principles, you can make good judgments on the information that you pick up here and there, and you can decide what suggestions are worth to follow and what others are not. The book can be ordered online at www.pigeonbooks.com
You should understand right at the beginning that biology is not mathematics. Nothing is as sure in biology as 2x2=4 in math. Biological systems are far more complex than we could just consider anything 100% sure (except death). In such “multi-factorial” systems we can only talk about possibilities and likelihoods, good chances and poor chances but there is no absolute truth carved in stone.
Furthermore, nothing is black and white in biology. Everything has two sides; advantages and disadvantages. You should always consider both sides, the benefits and the risks before making a decision. But you must always try to take all benefits and all risks into account. If you just arbitrarily pick some benefits and some risks, your balance sheet will be misleading, and your decision may not be right. To be able to see all benefits and all risks (or at least most of them), however, you should learn the basic principles.
In this article I have tried to describe the general principles of vaccination because vaccination plays a critical role in pigeon health management (as well as in that of other species including humans). It is important to understand what vaccines do and how they work because the current anti-medication propaganda that started against antibiotic abuse does not necessarily apply to vaccines.
Here, I do not want to deal with antibiotics and with the damaging effects that their inappropriate use may cause to pigeons. Instead, I would refer to Dr. Talaber’s book, Pigeons and Their Economical Health Care, where he describes this topic in general and in great details. I cannot add anything to it.
I only want to focus on vaccination here but a brief comparison of the two seems to be necessary.
The difference between “antibiotics” and “vaccines” and how it relates to “cure” and “prevention”
Vaccines and antibiotics are two totally different categories. Their mechanism of action is profoundly different. You cannot compare them as you cannot compare an orange with a banana.
So, what’s the difference? There are many differences but here, I only want to focus on the main difference that determines the way they are used. And this is the followings:
Antibiotics act on bacteria while vaccines act on the pigeon’s immune system. In other words, antibiotics kill bacteria in the pigeon’s body by direct contact with the pathogen. The protective effect is immediate and short term (hours or days). Vaccines, however, indirectly “kill” the pathogen through the pigeon’s immune system. Vaccines do not need direct contact with the pathogen. Their effect is not immediate as the immune system needs some time to develop protection, therefore, vaccination must always precede infection to be effective. The protective effect of vaccination is long term (months or years).
This may sound obvious to some but all other differences derive from this basic statement. For example, we can now understand why antibiotics are ineffective for prevention* while preventive application is the ONLY appropriate way for vaccines. We can write down these equations:
Vaccines = to prevent infections (both viral and bacterial)
Antibiotics = to cure infections (only bacterial)
* Please note that “preventive” antibiotic treatment for paratyphoid is NOT really preventive because Salmonellas are present in the pigeons’ intestines even though they are not causing clinically manifested symptoms. Therefore, antibiotics can make direct contact with the pathogens and kill them. The term “cleansing” antibiotic treatment is a more accurate name in this case.

What is vaccination?
The historical name, vaccination refers to the first vaccine that was prepared from bovine tissues (vacca = cow). It was hundreds of years ago, and cows have nothing to do with modern vaccines anymore.
Vaccination is the active form of immunization* when we make an animal (or human) resistant (immune) to a pathogenic microorganism by administering its non-pathogenic variant either orally or by injection. The principle of vaccination is based on the fact that different parts of a microorganism are responsible for its antigenicity and for its pathogenecity.
Antigenicity means the capacity of eliciting an immune response in the host system, and the molecules that are responsible for it are called antigens. Although antigens are just small parts of the whole microorganism, the immune response they induce in the host animal is able to neutralize the whole pathogen.
Pathogenecity means the capacity of causing disease in the host system. It is much more dependent on the integrity and viability of the microorganism than antigenicity. In other words, pathogenecity is much more susceptible to any change in the structure of the microorganism than antigenicity. This is what we utilize in vaccination when we modify the structure of a pathogenic microorganism so that it loses its pathogenecity while retaining its original antigenicity.
* There are two forms of immunization: 1) Passive immunization and 2) Active immunization or vaccination. The former has much less significance than the latter and is totally irrelevant in pigeon health care. Therefore, we do not discuss it here. Passive immunization plays a significant role in venomous snake bites for example when we administer “ready-to-use” antiserum AFTER the bite. It is not for prevention, it is for emergency treatment (just like in case of antibiotics).

Different types of vaccines
Vaccines have long been in use but only relatively recently, with the advance of molecular biology, we started to really understand how they work. Understanding better also means controlling better which results in more effective and safer vaccines.
As we discussed above, pathogenecity is more susceptible to changes in viability and molecular structures of a microorganism than antigenicity. Therefore, we can make modifications to a pathogen rendering it non-pathogenic while its original antigenic structure is still preserved. This is how vaccines are prepared. Different methods have been used to eliminate pathogenecity of a microorganism and make it suitable for a vaccine.
1. Killed vaccines
The most obvious method to make a pathogen microorganism suitable for a vaccine is to kill it. However, the strong chemical agents (e.g. formaldehyde) that are used for killing the pathogen also make changes in the antigenic structures which results in decreased ??? immunology ??? protective effect. Also, killed pathogens are quickly eliminated from the host and their immunology protective effect is usually shorter than that of live vaccines.
Important note: The chemicals used for killing the pathogens do NOT remain in the vaccine. They are washed out and the killed pathogens are diluted in a neutral solution in the final product.
2. Live vaccines
A more gentle way of rendering pathogens harmless is to artificially induce mutations in their genetic structure that results in less viable and less pathogenic strains (attenuation).
Live vaccines have advantages and disadvantages compared to killed vaccines. The antigenic structures are usually more preserved in live vaccines and thus, their protective effect is stronger. Also, because the microorganisms in live vaccines are usually capable of limited proliferation in the pigeons’ body, they are not eliminated as fast as killed vaccines and thus, they provide longer lasting protection.
On the other hand, live vaccines pose a relatively higher risk to the host system as – although rarely – they may regain their virulence and cause illness or side effects.
3. Recombinant vaccines
These are vaccines prepared by the most advanced bio-medical technologies. By sophisticated genetic engineering methods scientists can isolate the genes that are responsible for producing the antigens in a pathogenic organism, and put these genes into a harmless microorganism that will start to produce the corresponding antigens in high quantities. In this way, we can prepare recombinant vaccines that only contain the harmless parts of the pathogen (the antigens). The name “recombinant” comes from the fact that different parts of two unrelated microorganisms are combined into one new strain that will produce useful molecules for us.
Recombinant vaccines are highly purified and because they do not contain the complete microorganism, the risk of side effects is usually minimal. However, for the same reason, as killed vaccines get quickly eliminated from the host system, recombinant vaccines usually provide shorter protection than their live counterparts.

Vaccines used in different species
Pathogenecity of a certain microorganism may be restricted to one species only or it may cause disease in more than one species. The pathogenecity of each paramyxovirus strain, for example, typically restricted to one species while a salmonella strain is capable of causing disease in several species. Either case, however, the antigenicity of closely related strains is similar. This is what we can utilize when there is no pigeon vaccine available. The chicken Newcastle vaccine used in pigeons is a good example for this practice. Please note that when pigeon vaccine is available, it is always a better choice than one produced for other species.

The immune response
The immune system is a powerful multi-level defense mechanism with the capability of recognizing the differences between self and foreign molecular structures. Everything that is recognized as “foreign” will be the target of a powerful arsenal of different cells and molecules specialized in destroying and eliminating it. (Unfortunately, sometimes our immune systems mistakenly recognize some of our self structures as foreign, and this is when autoimmune diseases occur e.g. diffuse corneal opacity in pigeons.)
The first level of immune response
The first level of immune defense is not antigen-specific which means it is not “customized” to a particular pathogen. Any intruder attacking the host system will face the same first line of immune defense which includes the skin, certain type of killer and scavenger cells. This non-specific defense mechanism responds to foreign attackers immediately, but its efficacy is very limited. It is only capable of defending the body against weak attacks. If the pathogens attack in high number, and/or they are resistant to the non-specific immune response, they will easily break through this first line of defense, and the fate of the host system depends on the second level of immune response.
The second level of immune response
The second line of defense mechanism is an antigen-specific immune response (will be explained later). It is much more powerful than the first level but it needs a certain time period to be launched.
There is a very important difference in the antigen-specific immune response depending on whether it is the first or a repeated encounter with the foreign substance (pathogen). If it is the first encounter, the immune system needs significantly longer time to respond to the danger than in case of a repeated encounter. The reason for this is that the immune system has to create “customized” (or antigen-specific) antibody molecules that will neutralize the pathogen. In case of the first encounter, this “customization process” takes at least a week to be completed. On the other hand, in case of a repeated encounter, this “customization process” is skipped because the immune system “remembers” the antigenic structure of the pathogen, and keeps a set of “templates” of the antigen-specific antibody molecules “on stock”.
Antibody
Produced by B lymphocytes. They are capable of targeting and attaching to antigens very selectively. By doing this they “tag” the pathogen, and this signal initiates a deadly process resulting in the destruction and elimination of the pathogen. You can consider an antigen and its antibody counterpart as a “key” and a “lock” on the molecular level.
Antigen-specificity (selectivity) is very important because this is the “aiming mechanism” of a deadly weapon in the immune system. If an antibody molecule would “miss” the target by attaching itself to a self structure instead of the pathogen, it would lead to self-destruction.
The antigen-specific immune response consists of the following main steps:
1. Taking samples of the antigenic structure of the intruder. This is done by a certain type of immune cells called “antigen presenting cells” (macrophages). They internalize the foreign substances (phagocytosis), and cut them into smaller pieces before “presenting” them on their cell surface to other immune cells (T lymphocytes). This step requires just a few hours to be completed.
2. Creating “moulds” of the antigens that are the 3-dimensional negative impressions of the antigens on the molecular level (key-lock analogy). These “moulds” will be the templates of the antigen-specific antibody molecules that the immune system will produce in high quantity. This step requires a week (!) to be completed.
3. Antibody production. Once the “template” is created, a large scale production of identical antibody molecules starts to develop. Since the capacity of a single antibody producing cell (B lymphocyte) is limited, a vigorous proliferation of these cells is induced to multiply the output of the system. This step requires a couple of days.
Once a high blood level of specific antibody has reached, the pathogens are usually killed and eliminated from the circulation and from most organs. However, they may further survive in organs where the circulating antibodies and immune cells cannot reach them, for instance in the digestive system in case of Salmonellas (paratyphoid) or inside neuronal cells in case of Herpes virus.
Relatively high antibody level may persist for several months protecting the body from new infections. However, it would gradually decline unless subsequent encounter with the pathogen induces a new surge of antibody production. Such a subsequent encounter may occur in the form of natural infection or booster vaccination.

Please note that in the first encounter with the pathogen a minimum of 10 to 14 days are required for the immune system to launch an effective counter-attack. If the immune system has already been “introduced” to the pathogen (through natural infection or vaccination), this lag period is only 3-6 days (because the “customization” step is skipped). Furthermore, the still persisting antibody level from the previous encounter provides a temporary protection until the new surge of antibody production starts.
I cannot emphasize the importance of this “lag period” enough because this is a life-or-death question! During this “lag period” the host animal is practically defenseless, and the pathogen can proliferate almost at its will. A few days difference is not JUST a few days difference. It is exactly what saves the birds. The next section explains it why.
How vaccines protect
We saw that there is a lag period in the immune response after the infection occurs. Fortunately, pathogens also need a certain incubation period to proliferate and cause clinically manifested diseases. This is also a “lag” period and the length of this period is a well-known characteristic of each pathogen. It varies between a few days to a few weeks. Pigeon paramyxovirus is a good example for an extremely long incubation period which can exceed 3 weeks. (This long lag period allowed fanciers to save some of their birds by vaccinating the seemingly healthy ones AFTER the first symptoms appeared in the loft in the early days when PMV just started to spread all over the world.) It is important to note, however, that the exact lag period in a particular case highly depends on the initial amount of pathogens that entered the pigeon’s body. Obviously, the more pathogens entered the shorter the lag period.
Now, what happens when a pathogen infects the bird? A furious RACE starts between the pathogen and the bird’s immune system. A race to the death where the winner will survive and the loser will be swiped out. Now we can understand why it is so important that an effective immune response be launched as soon as possible.
Imagine a vaccinated pigeon whose immune system has already been “introduced” to the pathogen (through vaccination) and so it only needs 4 days to launch a full strength counter-attack on the pathogen after it enters the bird’s body. Let’s assume that the pathogen’s typical incubation period is 8 days before it can cause clinical symptoms. Now, imagine another pigeon, a naive bird whose immune system is unfamiliar with the pathogen and so it needs 12 days to launch a full-strength immune response against this new pathogen. We can visualize what happens by a pigeon race analogy.
Pigeon A represents the vaccinated bird, and it is released 200 miles from the loft.
Pigeon B represents the pathogen, and it is released 400 miles from the same loft in the same time as Pigeon A is released.
Pigeon C represents the unvaccinated (naive) pigeon and it is released 600 miles from the same loft in the same time as the other two birds are released.
Unlike real pigeon races there is no adjustment and computing here. The first bird arriving at the loft is the winner and the last bird is the loser. That’s it. Can you make a guess who will be the winner?
This is, of course, a little exaggerated analogy but it serves well to understand the importance of TIME in the fight of the birds’ immune systems with pathogens. What vaccines do is nothing else than an early introduction of the birds’ immune systems to the most dangerous pathogens and, if later, a natural infection occurs, the birds have much better chances to survive than naive birds.
Now, we can answer the initial question: “How do vaccines protect our birds?” The answer is this: With vaccination we “mimic” a natural first encounter with the pathogen under controlled circumstances using non-pathogenic variants of the wild type pathogens. We can control at least two important factors in vaccination that are beyond our control in natural infections. These are the following:
1. The amount and virulence of pathogens (antigens)
In natural infection we cannot control the amount of the pathogens that enter the birds’ systems. If a massive infection by a highly virulent strain occurs in a naive flock, the birds may die before their immune systems would have a chance to develop an effective counter-attack. The amount of the antigens in vaccines, however, is carefully determined and controlled.
2. The time of the first encounter with the pathogen
Probably I should have put this factor in the first place because its importance tremendously increased since we have CIRCOVIRUS around. The effect of Circovirus in pigeons is very similar to that of HIV in humans. It attacks and destroys the immune system so that it cannot defend the birds against infections anymore. Therefore, it is extremely important to introduce (by vaccination) the pigeons’ immune systems to the most important pathogens at the earliest possible time before they get infected by Circovirus. Due to its high importance, the effect of Circovirus infections on our vaccination strategy is discussed in a separate section (see next).
Another important consideration of the time of the birds’ first encounter with the pathogen is that nobody wants it to occur during racing season. However, if naive birds are entered in the race, they have a very good chance to be exposed to many different pathogens and, considering the stress the race put on the birds, their immune systems will likely to succumb to these pathogens.
Furthermore, by vaccination we can choose a time for the firs encounter with the pathogen when our pigeons are known to be in good health with strong immune status. In contrary, natural infections may hit our flock when its general health and immune status are rather weak. In this case even survivors cannot build a strong, persisting protection from natural infection.

Vaccination in light of the threat of Circovirus infection
I cannot explain this issue better than my colleague and friend, Dr. Talaber did in his books (www.pigeonbooks.com). Therefore, with his permission, I quote some parts of his “Circovirus” section below.
This is a new and very significant problem that in many places has not yet been recognized, and which is likely to cause enormous problems in pigeon-fancying in both the shorter and longer term...
...In pigeons, circoviruses attack and destroy the cells of the lymphatic organs (the spleen, the thymus, the Bursa of Fabricius), which make up part of the body’s defence mechanism, and so they resemble HIV, which leads to AIDS in humans. Afterwards, the weakened immune system is no longer capable of fighting other pathogens, either, and so a specimen infected with circovirus can in theory fall ill from any pathogen; indeed, even harmless microbes can attack it...
... In many countries there is still no real data on the incidence of circovirus in pigeon flocks. It is conceivable that a comprehensive survey would yield results as surprising as those found in Scotland. The virus was first identified there in 1994, and a recent research programme investigated the birds of 17 flocks. The results were devastating: in 14 cases out of 17, yards proved to be infected with circovirus.
The general picture is just possibly not quite this tragic, but we should certainly assume that infection with circovirus has a very negative effect. As it is the immune system that the virus damages, an affected specimen, even if it does not appear ill, will react badly to the usual vaccinations, if at all. For this reason, if for example we were to vaccinate a pigeon infected with circovirus against paramyxovirus, the vaccination will not be successful: no protection will develop against the paramyxovirus, as the damaged immune system is incapable of providing a regular immune response to the paramyxovirus vaccine. This is true for other vaccinations, too, and this is why fanciers (and sometimes veterinarians) are often confused when a flock that has been vaccinated appropriately and repeatedly nevertheless becomes ill with e.g. paratyphoid.
The situation is a serious one. In any case, this is further proof that we cannot successfully protect the health of our pigeon flocks with medicines and vaccines alone. In connection to circovirus infections, too, we can say that traditional methods of protection seem to be regaining their value: prevention of epidemics, a consistent high level of hygiene, keeping birds in a stress-free environment with comprehensive nourishment, which all guarantee that the immune system will remain at a high level. We should by all means ensure strict measures of prevention of epidemics so that we protect young birds from becoming infected at least until they have received the most important vaccinations (more precisely, until those have taken their effect), as after any possible circovirus infection it is no use our vaccinating them against other illnesses. This is why the vaccination against paramyxovirus must be performed as early as possible, when the pigeons are three weeks old! In theory, we can vaccinate against paratyphoid from the age of four weeks, but this of course depends on a number of factors, including the vaccine used and when the vaccination against paramyxovirus takes place.

The limits of the immune system
The immune system is an amazingly sophisticated and powerful defense mechanism of birds and mammals (and even of amphibians, reptiles and fish). However, it has its own limits that we should be aware of when planning our health management systems. Its main limitations are the followings:
The limits of the non-specific immune level (the first line of defense)
The intact skin especially if covered by a thick layer of hair (mammals) or feather (birds) is an effective barrier preventing pathogens from entering the host system. However, in case of injury, this barrier is obviously broken and pathogens can directly infect deeper tissues. Another example is when infection occurs via blood-sucking arthropods (e.g. pigeon pox). They literally INJECT the pathogen into the bird’s body through the skin (just like vaccination).
The mucosal membranes of the respiratory and the digestive systems (or the conjunctiva of the eyes), however, are much less effective barriers against pathogenic microorganisms. It is no surprise that most infections start here.
The protection is even weaker if the mucosa is attacked by more than one pathogen. This is the case of a secondary bacterial infection, for example. The first attacker is usually a virus that causes inflammation in the mucosa. Then, bacteria that had already been present but unable to break through the barrier, now effortlessly enter the body.
We can see that natural infections can often circumvent the protection of the skin (through injuries) or easily break through the mucosal membranes.

The limits of the specific immune level (the second line of defense)
1. Lag period
The immune system needs a certain time period to recognize the foreign intruders, take samples of their molecular structure, create a “customized” set of antibody molecules and produce them in high quantities. We saw earlier that the length of this lag period highly depends on whether this is the first or repeated encounter with the pathogen. In the first encounter the lag period is 10-14 days during which the bird is practically defenseless against the pathogen. In case of deadly pathogens this may cost the bird’s life.
2. The immune system’s susceptibility to stress
It is well known to fanciers that stress has a strong negative impact on the birds’ immune systems. We should always try to minimize the stressors, but sometimes this is not an easy task. A race itself or even transportation before the race, for instance are strong stressors. The only way to avoid them is not to fly pigeons. But that would be the end of pigeon racing. Other stressors like extreme hot, breeding or rearing the young are even more difficult to avoid.
If a massive natural infection occurs during strong stress, naive birds have much less chance to defeat the pathogen than vaccinated ones.

Risks and benefits of vaccination
We always make choices in our everyday life based on risks versus benefits calculations. We are so accustomed to taking risks that do not even keep them in our conscious mind. Think of driving a car. Are you constantly aware of the huge risk you take when driving on the highway at 60 mph? And are you constantly aware of the serious negative effects that the release of carbon monoxide (CO) and other poisonous gases by cars cause to your health, to your children’s health and to the environment? Would you completely give up driving your car if somebody explained to you all the risks and damages? I do not think so because you would make a risks versus benefits calculation and would figure out that driving your car still has more benefits than risks. But your raised awareness about all risks and damages may change your attitude. When you only have to go a quarter mile, you would take a walk instead of jumping into your car. It would be good for your health and for your environment. Also, next time you would prefer buying a smaller car that emits less damaging gases than a monster truck.
When the question arises whether we should vaccinate our pigeons or not, we do the same risks versus benefits calculations. To create a fair “balance sheet” we should consider the following.
We should always consider the risks and benefits individually for each vaccine and for each flock. The risks and benefits widely vary depending on the disease in question, the type of the vaccine (killed, live or recombinant) and the general health status of the flock.
For example, the expected benefits of a vaccine for a deadly disease are certainly much higher than that of a vaccine for a mild disease. Thus, even if the former has a relatively greater risk of side effects, you may want to protect your flock against the deadly pathogen by vaccination while let your pigeons deal with the less serious pathogen on their own.
Also, if you have scheduled a vaccination for today but your flock is under a strong stressor right now (e.g. due to extremely hot weather), you may not want to take the risk of serious adverse effects and postpone the vaccination.
I hope my article made it clear that the active ingredients (antigens) in vaccines do NOT pose higher risks to pigeons than natural first encounters with deadly pathogens. Quite the opposite is true. Even if a non-pathogenic or an attenuated version of the pathogen in the vaccine causes a mild reaction, this is much less of a burden on pigeons than a natural first encounter with the wild type pathogen. A mild reaction after vaccination is natural and even desirable. This is how vaccines work.
Solvents, preservatives and other additives in vaccines may pose a risk to the pigeons. The Food and Drug Administration (FDA) in the US requires rigorous tests to be performed before a drug including vaccines gets approval and registration. These tests include but not limited to efficacy tests, toxicity tests, kinetic tests (ADME – absorption, distribution, metabolization and elimination). Unfortunately, even with all these rigorous tests there might be ingredients in vaccines that are damaging to pigeons. We should be aware of this risk and make informed decisions when planning our flocks’ health management programs. It is like with antibodies; do not overuse them but when they are needed, use them with caution and always in accordance with the instructions and with your veterinarian’s advice.
Note! Although we use the terms “natural immunity” and “artificial immunization”, the distinction is not so strict. Artificial vaccines trigger the same exact natural immune processes in the host’s body as natural infections. The only difference is in the very first step, in the way the immune system is introduced to the antigens.
Important! Not only vaccination has risks. Not vaccinating your flock also has its own risk. The degree of such a risk depends on
- the virulence and occurrence of the pathogen in question,
- the expected protective effect of the vaccine you are considering to skip, and
- the possibilities of curing the disease if contracted.
 
 
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