The measles virus is untreatable. In about 30 percent of affected patients, many of whom are infants and children, complications can lead to blindness, as well as pneumonia and inflammation of the brain—both of which are potentially fatal.
Despite the availability of a safe and effective vaccine, the Centers for Disease Control and Prevention (CDC) reports 214 measles cases have been diagnosed in the United States this year, an increase of more than 478 percent from the 37 cases that were reported in 2004. In Europe, the number of infected patients has quadrupled in the past two years and now amounts to nearly 41,000, a record high.
Globally, in 2016 about 90,000 people died from the measles virus, according to the World Health Organization (WHO). The disease affects an estimated 20 million people in developing countries, countries in which health infrastructures are weak and access to the MMR (measles, mumps, rubella) vaccine is limited. In the United States and Europe, however, longstanding anti-vaccination movements are responsible for the recent outbreaks.
Measles, which should have been eradicated in places equipped with the requisite public health resources, has resurfaced because of misinformation, which caused unwarranted fears about a link between immunizations and autism. Meanwhile, progress in the fight against diseases including measles is threatened by efforts to stop animal research in science and medicine. Together, animal rights groups and the anti-vaccination movement represent twin symptoms of the same problem: science-denial. And, clearly, the consequences can be devastating.
MMR is administered in two doses. The first is recommended for babies between 12 and 15 months of age, and the second for children between the ages of four and six. Parents who choose not to vaccinate their children also put at risk the health and safety of unvaccinated newborn infants, who, by virtue of their underdeveloped immune systems, are especially susceptible to developing life-threatening complications from measles.
Medical advancements have substantially curbed the impact wrought by the measles virus in countries around the world. And from the development of MMR to the discovery of new medical knowledge about the disease, animals have played a critical role.
Using cell cultures procured from chick embryos, Maurice Hilleman found a new preparation of a live attenuated (weakened) strain of the measles virus—which, following seven years of animal testing, became the first “M” of the MMR vaccine that was introduced in 1971. In additional studies with animals, researchers have discovered more effective formulations while determining the optimal vaccine dosages and schedules. At the same time, these studies produced a library of evidence that demonstrates the safety of MMR, which, according to WHO, saved more than 20 million lives from 2000 to 2016. Preclinical research—which, in the study of vaccines, involves calves, cattle, pigs, sheep, horses, smaller animals, and monkeys—remains just as vital today in the search for new ways to prevent disease.
For example, the University of California, Davis National Primate Research Center recently published a five-year study in which MMR was administered to newborn rhesus macaque monkeys. The absence of any adverse effects or complications suggests the vaccine might be safe for human infants younger than 12 months of age. If future research leads to this conclusion—it could be lifesaving.
In addition to humans, monkeys are the only animal species susceptible to infection with the measles virus. Marmosets, squirrel monkeys, and spider monkeys are especially vulnerable to the disease, which can cause widespread mortality in animal populations. While some vaccines approved for human patients can safely and effectively protect monkeys against measles, animals living in captivity are often not immunized because of the high cost. Researchers have sought an alternative formulation and investigated options including MVac, a cheaper freeze-dried preparation of the vaccine, which is approved by the WHO for administration to people. Encouraged by the results of preliminary testing with rhesus macaque monkeys, researchers recommend further studies to determine whether the vaccine should be adopted for widespread use in colonies of non-human primates.
Opposition by animal rights activists to the inclusion of animals in preclinical research effectively represents a denial of science, of the substantial evidence that points to its vital role in medicine. Likewise, people who adhere to the belief that vaccines can cause autism must deny the overwhelming evidence that has effectively disproven any potential link.
The vaccine controversy began in 1998, after a researcher published a study involving only 12 children who, he claimed, developed autism shortly after the administration of MMR. Subsequently, it was discovered the paper contained numerous deliberate falsifications and it was fully retracted by The Lancet medical journal. Unfortunately, the research community’s disavowal of the study did not stem the tide of misinformation, which led to widespread concerns among parents about vaccine safety.
Motivated by the public’s fears, scientists employed every methodological approach in the research arsenal to look into potential links between MMR and autism: Studies of human gastrointestinal and immune systems; large-scale epidemiological research (including a 2012 analysis that included more than 14 million children); statistical models; and—crucially—research with animals. None has found any association between vaccines and autism.
If public health resources in the United States and Europe can be effectively marshalled to defeat the anti-vaccination movement, the number of reported cases of diseases like measles (along with whooping cough, diphtheria, tetanus, and others) could fall to zero. In the developing world, meanwhile, a host of challenges are responsible for lower vaccination rates and higher incidence of disease.
One hurdle is presented by the two-dose MMR schedule—the most effective way to prevent measles infection—which was adopted in the United States, United Kingdom, and a few other countries as recently as the 1990s; elsewhere, it remains standard practice to administer only one dose. In many places, the scarcity of economic resources presents the most difficult barrier to implementing successful vaccination programs. While immunization costs in the developing world were traditionally low, the number of suppliers has dwindled, driving up costs that can be prohibitive in countries where people live on as little as $2 USD per day. Additionally, in areas with poor healthcare infrastructures, it can be impossible to properly handle and store the vaccine. The US Department of Health and Human Services specifies which temperature ranges, light exposures, and even which places within the refrigerator are acceptable. Environmental factors can affect the efficacy of doses; for example, uneven temperatures at the floor and in the door of the refrigerator can lessen the potency of the MMR vaccine.
Fortunately, some of these challenges could potentially be addressed with a recent discovery that was reached in a study with ferrets. An experimental drug safely and effectively prevented infection in the animals with a virus closely related to measles. If proven successful in human clinical trials, the researchers envision the “shelf-safe” medication could be stockpiled to serve as an alternative to MMR, possibly with a single-dose schedule. Such a development would likely have a meaningful impact on measles prevention in the developing world.
Smallpox, one of history’s deadliest diseases, killed between three and five hundred million people in the twentieth century despite the introduction of an effective vaccine in 1796—which was developed by research with calves. It took a long time before international relief efforts could fight the disease overseas, namely via the WHO’s smallpox program, which was begun in 1968. The slow rates of vaccination can be attributed in part to some of the same social and behavioral factors at play today (along with infrastructural and technological challenges unique to the nineteenth and early twentieth centuries). Regardless, as a result of those global vaccination efforts, the last naturally-occurring case of the smallpox virus was reported on April 14, 1978. The total eradication of measles, too, could one day be achieved in much the same way.
Inroads in the fight against deadly diseases are only reached, though, by supporting research and rejecting bad ideas (including those which originated from bad science). Medicine and public health aspire to lofty goals: Preventing, curing, and eradicating disease; relieving pain and suffering; forestalling death; developing public policies that support health; educating the public; cultivating a skilled health workforce and sophisticated infrastructure; investigating health hazards; and promoting research. None are well-served by the denial of science via either the circulation of discredited ideas about vaccines or the opposition to animal research.
By Christopher Kane