Many infections found in animals are not transmissible to humans and reversibly. The same diseases-causing pathogens can infect different animal species, but the diseases they cause often take a very different form in those animal species. This is the reason why AIDS, hepatitis, rubella, typhoid, leprosy, yellow fever, malaria, Epstein-Bar syndrome, influenza, mumps, measles, and Creutzfeldt-Jakob disease are found in humans but not in other animal species. For example, rabies is very rarely present in humans. Other diseases like anthrax, and Ebola can infect both animals and human beings.(2) In the 19th century, vaccines were commonly created and tested on animals because the belief that infectious diseases could be transmitted from one species to another was very strong; today we know that this assumption is not so simple.

Pasteur's 'germ theory' and Koch's postulates encouraged the use of animals in order to "reproduce" human diseases. The fist polio vaccine was made using monkey cells but today it is considered safer to use human tissue; not only is there less risk to spread animal viruses in human populations, but also the vaccines developed using human tissue are more efficient. There is ample documentation proving that the first successful vaccines derived from animal testing actually killed the human subjects who tried them, like Koch's tuberculosis vaccine, or Pasteur's rabies vaccine. This is to say that animal testing did not reduce the risks to prevent death and suffering in humans.

Although the testing of vaccines on animals does not give a scientific account of the response in human beings, it can give some clues. However, the reliance on the animal model is strong and up to 10% of laboratory animals are used to produce and test the potency and safety of vaccines, in Europe.(3)

The dose of vaccine needed to have a 50% effect on animals (ED50) and the dose of vaccine that protects 50% of the animals receiving a challenge (PD50) are not indications that can be reliably extrapolated to human beings. Due to major differences in their immune system, and the nature of the infectious agents, animal species have evolved with physiological responses of their own.

In the laboratory, the infective strain is placed in an artificial environment that differs from that of the wild strain. The route of transmission is different as well. Serological tests in animals do not provide indication that the vaccine is effective. There are many concessions made to the ideal situation of testing vaccines in its natural host, and they should not prevent the development of alternatives.

Fortunately, increasingly vaccines are produced in vitro; Some vaccines do not require routine potency testing on animals (oral typhoid, measles, mumps, influenza, hepatitis A and B. A rabies vaccine for veterinary use is being developed by immunochemical methods that determine the glycoprotein content of the virus, rather than the classical challenge in mice. Challenge in animals are no longer the gold standard in testing vaccines.(4)

Moreover, live vaccines can revert to a virulent form, and in immunosuppressed individuals, this situation can be life threatening; side effects occur, such as allergic reactions, contamination with animal viruses or chemicals used to produce the vaccines. Some vaccines have been linked to demyelinating disorders and cancers in humans.(5) Administering a vaccine is not something to be taken lightly and pharmaceutical companies know this fact too well; that's the reason why companies prefer not to invest money in the production of vaccines.

The active lobby groups that support animal experimentation claim that vaccines were discovered using lab animals, which is right since using laboratory animals was a dogmatic rule during the 19th century and even today. But today some vaccines do not require animal testing and there is a significant progress wherever human tissue is used instead of animal tissue. They also claim that thanks to vaccination (therefore animal experimentation), millions of people have been saved. Certainly, millions of people were "saved" because they were not in contact with disease-causing agents, in the first place.

The correlation between vaccination and the drop of mortality can be poor, suggesting that vaccination was not responsible for saving lives. Actually, a natural decline of infectious disease is more likely to be the cause of the drop of mortality in some cases. Better nutrition, hygiene, and quarantine are the real factors that account for the disappearance of infectious diseases.(6) Bubonic plague killed millions of people during the Middle Age, and vanished as mysteriously as it came. What about SARS (Severe Acute Respiratory Syndrome), which provoked a wave of panic in Canada? In fact, simple rules of hygiene and quarantine, again, made the virus recess. Also, people can suffer the consequences of vaccination campaigns sponsored by the government and the pharmaceutical giants.

SV-40 is a virus present in monkey cells and nobody knew about it when the polio-vaccine was produced. Now, the SV-40 has turned up into humans with unpredictable effects like cancer. How can we screen for viruses that we know nothing about? Maybe simple precautions would prevent a disaster like the Mad Cow Disease and the spread of transmissible encephalopathies in the human population or SARS or the Avian Flu Viruses. Our food production system create animal products addiction, animal waste, animal organs, animal-based vaccines, DNA and proteins, all exposing humans to potential dangers such as animal viruses; because of our lack of information, keeping our interactions with animals as limited as possible is one way to prevent diseases.

In the case of AIDS, our understanding about HIV comes from in vitro experiments on human tissue and cells and medical progress in this field, like so many others, hinges on learning about human biology and how humans respond to treatments. This is how we might be able to understand diseases and find treatments. AIDS vaccines will become safer and more efficient and available quicker if testing is done using human-based systems.

Another example of recent failure we owe to animal-based research is the latest vaccine to treat Alzeihmer's that was tested successfully in mice, but it induced brain inflammation in the patients that volunteered to take it. The trial was stopped.(7) Animal-based research provides a lot of useless information, is costly, and creates a great deal of confusion that delays true medical knowledge.

In contrast, human-based research is the best method that we can think of, it provides an increasing accuracy and confidence and it reduces the rate of failure in our quest for good solutions. Science is more than just an activity, through which researchers gather enough data to select only the hits (in the same way someone would place enough coins in a slot machine to win the jackpot.) Science must also evolve and constantly look for better methods that are truly scientific and test sound hypotheses.