On one side of the field, we have Hollywood starlets, activist-parents of autistic children, and a rash of opportunistic politicians – all lining up to condemn the nation’s immunization program for young children.

Over the last decade, this fervent coalition has convinced more and more parents that routine childhood injections against diseases like measles and mumps are causing autism and should be avoided at all costs. As a result, child vaccination rates are declining and infectious outbreaks are increasing at an alarming pace.

On the other side of the field, we have worried public health officials, the increasingly angry parents of immunized kids, and overly enthusiastic pharmaceutical sales reps – everyone else with skin in the game. The counter-movement is scrambling to discredit anti-vaccination rhetoric before things get even more out of hand. Parents are fighting parents, patients are fighting doctors, and the nation’s once-sacrosanct vaccination program is facing its greatest challenge to date. Read on to learn what each side is saying in the great vaccination debate.

Do Vaccines Cause Autism?

No, vaccines do not cause autism. At least that’s what establishment scientists and public health experts say. There is no vaccine that has been proven to cause autism, and no credible evidence supporting a causal link between them.

In fact, virtually all the science points to the low-risk nature of mainstream vaccinations, and the high-risk consequences of failing to immunize one’s children. The most recent generation may not remember what it was like when there was chronic measles outbreaks and rampant disfigurement caused by polio. It was a nightmare we learned how to prevent with vaccinations.

Not so fast, say anti-vaccination activists, including high-profile entertainers like Jim Carrey and Jenny McCarthy. Vaccines are stuffed with unnatural poisons, including known neurotoxins like mercury and aluminum. We’ve got a bona fide epidemic of autism and cognitive-learning disorders on our hands. Parents are scared. They demand an explanation. It could be in the shots. The U.S. immunizes kids at a much higher rate than other countries. The recommended CDC immunization schedule has most kids receiving some 50 shots by the time they’re six, thanks in part to industry lobbying. As we’ve added more shots to the roster, we’ve seen more young children with autism. What if it’s not a coincidence?

Too Many Exceptions, Too Much Risk

If it were just a matter of personal choice, authorities might not be so concerned with the growing number of unvaccinated children among us. But it’s not, experts say. While suspicious parents believe they are simply protecting their own children, those ‘personal’ decisions are actually endangering other people.

Immunity really occurs at the population level; you need very high overall rates of immunization for disease prevention programs to work. An unvaccinated minority can easily expose the most vulnerable individuals in the population to a Pandora’s box of debilitating maladies. That’s what happened in San Diego in 2008, for instance, when a startling measles outbreak started by just one unvaccinated student was spread by infants too young to have their shots.

Too Many Chemicals, Too Soon

We’re not letting vaccines off that easy, say anti-vaccination activists. Take Merck’s measles-mumps-rubella (MMR) vaccine, given to children in two stages starting at age 12 to 18 months. This triple whammy was singled out as a hidden cause of autism in a famous case study by the British physician Dr. Andrew Wakefield.

Wakefield’s study was published in a prominent journal in 1998, but was quickly pulled and thoroughly retracted. He was censured by medical authorities for ethical violations and eventually lost his license to practice. But supporters say Wakefield was targeted because his controversial work posed a threat to the pro-vaxx establishment.

Even discounting Wakefield’s claims, injection opponents say, there have been reports of other harms from the MMR vaccine. The National Vaccine Information Center (NVIC), a vaccine safety advocacy group, says nearly 900 claims have been filed alleging injuries and deaths following MMR vaccination, as of 2012. The MMR vaccine, it seems, is far from perfect. But does it cause autism?

An Epidemic or an Epic Figment of Imagination?

Anti-vaxx parents say the chemical cocktails in shots are just too much and too soon for little ones with their fragile immune systems. The proof is in the mysterious explosion of autism, which has yet to be explained by public health officials.

But is there really an autism epidemic?

It’s true that there are more reported cases of autism than ever before. Today, 1 in 68 children has an autistic diagnosis, and the number rises every year. And yet – the official tally reflects more than just raw prevalence.

Over the years, we’ve seen an expansion of the definition of autistic-spectrum disorders, a huge increase in parents' awareness of symptoms, and liberalization of state diagnosis rules. These changes tend to result in more cases on the record, but they do not necessarily indicate a rise in the actual prevalence of autism.

Many researchers do not believe there is an autism epidemic at all, but that the rising numbers simply reflect successful efforts to document and treat the disorder. We just didn’t know how many autism cases there were back in the ’50s. Now, we know better.

The True Public Health Threat

Science says vaccinations save millions of lives – a clear win for civilization. But do they also cause autism? Where does the true public health threat lie?

For the pro-vaccination establishment, childhood shots represent a net gain for society. No solution is perfect, but the case against shots like MMR has been greatly exaggerated. They say we owe it to our kids to protect them from deadly but preventable pathogens.

For anti-vaxxers, the American injection schedule remains guilty until proven innocent. They believe we owe it to our kids to protect them from brain-warping shots and government needles.

No matter which way you look at it, the fracas over immunization safety is flirting with high stakes. Let us hope the debate is resolved with minimal harm to the innocent kids caught between the warring parties.