The story of once conquering measles in the U.S. is one of triumph of biomedical research and public health policies. The tragic story of its resurgence is a reflection of the dangerous attractiveness of pseudoscience and of parents who refuse vaccination for their children.

Medical research by giants such as Dr. Maurice Hilleman has given us the tremendous privilege of protecting our children against one of the most contagious diseases known to mankind. I believe he would be devastated to learn that children are suffering needlessly because of superstition, conjecture and false science.

An unvaccinated, measles-infected visitor to Disneyland leads to a multi-state outbreak. A boy whose immune system is weakened by chemotherapy cannot attend school because of fears that he will be exposed to measles in his classroom. A college student with measles who rode Amtrak prompts N.Y. public health officials to instruct unvaccinated fellow travelers to visit their doctors.

Medical research by giants such as Dr. Maurice Hilleman has given us the tremendous privilege of protecting our children against one of the most contagious diseases known to mankind. I believe he would be devastated to learn that children are suffering needlessly because of superstition, conjecture and false science.

These are stories that we as infectious disease doctors never expected to hear in the U.S. in 2015. Already this year, more than 100 cases of measles have been diagnosed among people in 14 states. This dangerous virus is back, because too many parents decide to not vaccinate their child against this potentially deadly disease. Of course, it not only puts their own children in harm’s way but places many others at risk too.

The Measles-Mumps-Rubella (MMR) vaccine was invented by Maurice Hilleman, a remarkable scientist, whose work has been credited with saving many millions of lives.

Measles vaccination allowed a greater than 99% reduction in the number of U.S. measles cases, compared to the pre-vaccine era. As president of the Albert and Mary Lasker Foundation, I am proud that Dr. Hilleman received the 1983 Lasker Award for Public Service in recognition of this work. But in recent times, his work has been wrongfully undermined.

In 1998, a bogus study by Dr. Andrew Wakefield concluded that the MMR vaccine caused autism. Wakefield’s report was later shown to be fraudulent and retracted by the journal that published it. Ultimately, Wakefield lost his license to practice medicine for falsifying data.

Despite being debunked, Wakefield's false science was seized upon by desperate families looking to find answers to the mystery of why their child had autism and has been perpetuated by celebrities like Jenny McCarthy and by some religious leaders too.

There are other reasons that parents forego vaccinating their children: Some have forgotten the suffering that the measles virus can cause. After all, it's been rarely seen in more than a decade.

Still others have relied on “herd immunity” to protect their child. (Their reasoning is that if a high enough percentage of the population is vaccinated, the virus won’t be able to circulate, and their child will be protected.) But in the U.S. today, about 5% of children are not vaccinated and this number is even higher in some communities—enough to prevent the effectiveness of herd immunity.

Indeed, we’ve become more vulnerable. Last year, there were 644 cases in the U.S., by far the most in recent years. Although requirements that children be vaccinated to attend school have significantly increased immunization rates, more and more parents are electing to refuse vaccination on the basis of a “philosophical difference,” which is often broadly defined to include uninformed personal opinion and pseudoscience. Currently 20 states allow these “personal belief exemptions,” and many of the recent measles cases have occurred in children whose parents refused vaccination on this basis.

In many parts of the world, dire poverty and lack of access to health care prevent children from receiving vaccine -- not philosophical difference. While important programs have allowed 84% of the world’s children to receive the vaccine and have prevented an estimated 15.6 million deaths from 2000 to 2013, more than 145,000 people still died of measles in 2013 alone. The vast majority of these deaths were among children living in poor, developing countries. Their parents would have desperately wanted the vaccine protection for their children.

Medical research by giants such as Dr. Hilleman has given us the tremendous privilege of protecting our children against one of the most contagious diseases known to mankind. I believe he would be devastated to learn that children are suffering needlessly because of superstition, conjecture and false science. The MMR vaccine was a gift that has saved many millions of lives. Now it is up to us to ensure that all children have access to life-saving science.