No robust scientific evidence that animal tests reliably predict human safety and efficacy
Dr Jarrod Bailey, Senior Research Scientist
Amid the understandable panic and concern over the current coronavirus (COVID-19) outbreak, it is some comfort to see the scientific and medical communities making Herculean efforts to establish a sensible, evidence-based way through to reduce the number of deaths as much as possible.
Part of the medical response is the search for a safe and effective vaccine as soon as possible to afford the world’s population some protection. This will undoubtedly involve the use of animals in testing, which is something that we neither support nor think is effective or necessary. In fact, we are not alone in this, as reports from the US suggest that the first trial of a COVID-19 vaccine has begun in human volunteers following extremely minimal animal experiments. The fact that they feel confident enough with minimal animal data to proceed to human trials should be heartening news for those of us opposed to the harmful use of animals. Not only does this show that it is possible, but the reasons why they feel that they have had to take this step should encourage all medical researchers to look at the need for, and effectiveness of, animal testing going forward.
First, neither researchers nor the public can afford to wait for the usual lengthy animal tests to be done. Secondly the only supporting animal-based evidence came from a comparison of the immune responses of some mice to COVID-19, with the responses of mice to an experimental vaccine for a related coronavirus, MERS-CoV. These responses were considered to be ‘similar’, even though it appeared that the mice could not ‘catch’ COVID-19 in a similar way to humans. The scientists involved are breeding different mice they think will be more susceptible — though whether or not these mice are any more human relevant than the others is not known {Lanese, 2020, #525}. The mice were genetically engineered in response to the SARS outbreak in 2003 to make them easier to infect but aren’t currently available in sufficient numbers for research.
There is no robust scientific proof that animal tests are reliably predictive of human safety and efficacy. In fact, there is good evidence that animal tests do not reliably predict these things [1, 2], in addition to the simple fact that over 90% of new drugs that appear to be safe and effective in animal tests go on to fail in human trials [3, 4].
There is specific evidence for vaccines, too: an HIV/AIDS vaccine has been sought for more than three decades, with no success, in spite of hundreds of clinical trials of dozens of vaccine types showing promise and success in monkey tests [5]. Even if, in a worst case scenario, the vaccine did cause harm to people (which would likely be quickly evident in human trials), this harm would almost certainly be significantly less than the morbidity and mortality that is likely to ensue from future COVID-19 infections if we have no vaccine at all, while the world waits months or even years for the results of animal tests of, at best, poor human relevance. Even from a superficial perspective: if there are differences between different types of mice with regard to COVID-19 infection, how can we expect to apply data from just this one type of mouse to human beings? There are way too many genetic and biological differences in the way, many of which affect the immune system [6].
The chief medical officer at the drug company testing the new vaccine, and the president and CEO of the International AIDS Vaccine Initiative (IAVI), have been among people supportive of the recent commencement of the COVID-19 vaccine clinical trials. Cruelty Free International believes the quickest and most reliable way to realise a vaccine that protects people is to avoid animals completely, and to push ahead with careful, regulated clinical trials supported by human specific clinical research, and tests using human tissues and cells. This is underlined by current science in the news. Analysis of blood samples from a patient recovering from COVID-19 infection has greatly informed our understanding of human immune responses that take place, including the specific types of immune cells, antibodies and inflammatory molecules involved, and how these correlate with and may predict the course of infection and clinical outcome, as well as inform vaccine candidates and evaluate other interventions [7, 8].
Scientists are also investigating the potential benefits of using antibodies in the blood of people who have recovered from COVID-19 infection to boost immunity in newly infected and/or at-risk people. This concept, known as “convalescent sera”, has been used for around a hundred years, with notable successes for mumps and measles, and, it is claimed, could be set up and ready to go very quickly [9].
This is a necessary, evidence-based paradigm shift that is already happening in science, with increasing and irresistible momentum. The continued advocacy and defence of wasteful and misleading animal experiments isn’t just harming animals; it is also harming millions of people who are relying on science to do the right, most productive thing.
References
- Bailey J, Balls M. Recent efforts to elucidate the scientific validity of animal-based drug tests by the pharmaceutical industry, pro-testing lobby groups, and animal welfare organisations. BMC Med Ethics 2019;20:16.
- Bailey J, Thew M, Balls M. Predicting human drug toxicity and safety via animal tests: can any one species predict drug toxicity in any other, and do monkeys help? Altern Lab Anim 2015;43:393-403.
- Hay M, Thomas DW, Craighead JL et al. Clinical development success rates for investigational drugs. Nat Biotechnol 2014;32:40-51.
- Thomas DW, Burns J, Audette J et al. Clinical development success rates 2006-2015. Available: http://www.amplion.com/clinical-development-success-rates. 2016pp28.
- Bailey J. An assessment of the role of chimpanzees in AIDS vaccine research. Alternatives to Laboratory Animals 2008;36:381-428.
- Bailey J. Monkey-based research on human disease: the implications of genetic differences. Altern Lab Anim 2014;42:287-317.
- BBC News. Coronavirus: Australian scientists map how immune system fights virus. Available at: https://www.bbc.co.uk/news/world-australia-51921403. 2020. Accessed 18 Mar 2020
- Thevarajan I, Nguyen THO, Koutsakos M et al. Breadth of concomitant immune responses prior to patient recovery: a case report of non-severe COVID-19. https://doi.org/10.1038/s41591-020-0819-2. Nat Med 2020
- Casadevall A, Pirofski LA. The convalescent sera option for containing COVID-19. J Clin Invest 2020