In 2014, a New Jersey lawmaker introduced a bill that would allow certain children under age 6 to attend school without getting vaccinated against hepatitis B, asserting that the vaccine raised the risk of autism.

Yet there is no proof that this vaccine, or any other, causes autism.

While the proposal did not become law, it represented one of many such attempts to weaken requirements for vaccinating children, according to a new study led by Drexel University researchers.

From 2011 to 2017, state lawmakers in 18 states proposed 92 bills that could have reduced the number of children receiving vaccines — in most cases by making it easier to obtain exemptions, the study authors reported in the American Journal of Public Health. New Jersey legislators introduced 24 of the bills — the most of any state. (None were in Pennsylvania.)

One positive sign: During that seven-year period, lawmakers also introduced 83 bills that would strengthen vaccination rules, mostly by making it harder to obtain exemptions, and those proposals were far more likely to become law. Twelve of those bills were enacted, while just one of the 92 bills that weakened vaccine rules became law. That was a 2011 measure in Washington, allowing any health-care provider or naturopath to exempt children from getting vaccines — a power that previously had been limited to physicians.

The study results suggest that health officials need to increase efforts to promote the value of vaccines, said lead author Neal D. Goldstein, an assistant research professor in Drexel's Dornsife School of Public Health.

"I was encouraged because it shows that the legislative process works for pro-public health legislation," he said. "But it's discouraging at the same time to see the number of bills that were proposed that would hurt the public's health."

The findings come amid worrisome recent outbreaks of diseases that can be prevented with vaccines. New Jersey officials this fall have confirmed 15 cases of measles in Ocean County — an outbreak thought to have started with someone who contracted the illness abroad. North Carolina officials have identified 36 cases of chicken pox. Most children recover from these illnesses, but both can have severe complications such as pneumonia and even death. And the varicella virus that causes chicken pox can lead to the painful shingles rash later in life.

The New Jersey bill on the hepatitis vaccine, sponsored by Assemblywoman Holly Schepisi (R., Bergen and Passaic), was not taken up by the Legislature in its 2014-15 session or in the following session, when she reintroduced it. In an interview, Schepisi said the reference to a risk of autism originated with a previous version of the bill, sponsored years earlier by a different legislator.

"That was not my primary rationale," she said, adding that she was more concerned about other potential side effects of vaccines. For example, she said the chicken pox vaccine had caused a condition in her son called ataxia.

But vaccines do not cause ataxia either, according to a review of evidence by the Johns Hopkins Bloomberg School of Public Health. In fact, they can prevent it. Ataxia, a type of brain inflammation that affects muscle coordination, can be caused by infection with mumps or chicken pox — illnesses that can be prevented with vaccines.

As for the supposed link to autism, language in the bill illustrates the pitfalls that can occur when legislative staffers interpret medical literature, Goldstein said.

The bill cites a 2009 study in which boys who got the hepatitis B vaccine were reported to be three times as likely to have an autism-spectrum disorder as boys who did not get the vaccine. There was indeed such a study, but it had severe limitations. Among them: Identification of children as being autistic was based on a parental survey, not medical records. Some of the children in the study were born years before the vaccine was recommended by the federal government. And the authors excluded three-quarters of the children in the study because their parents did not supply proof of vaccination — preventing a true determination of any link with autism.

The bottom line: No large, well-designed studies have found any proof that vaccines cause autism.

Schepisi's bill would have allowed a child under age 6 to attend school without getting the hepatitis B vaccine if the mother had tested negative for the virus during the third trimester of her pregnancy.

Transmission during pregnancy is the primary way that young children are infected with hepatitis B, so Schepisi said that if the mother does not have the virus, it is fine for a child to wait until age 6 to get the vaccine. Upon reaching age 6, such a child would have had to get the shot unless a doctor determined it was not "medically suitable."

But other ways of becoming infected include: sharing toothbrushes, razors, or needles with an infected person; contact with blood or open sores of an infected person; and sex with an infected person, according to the U.S. Centers for Disease Control and Prevention.

"It is something where, by putting it off to 6 years old, unless you fall into a category of high-risk behavior, there is no other way of transmission," Schepisi said.

Such delays in vaccination make public health officials nervous. True, most young children are not exposed to hepatitis B, but the full protections of vaccines come with communitywide acceptance.

Delays in vaccination raise the risk that the parent does not follow through by taking the child for a return visit to the doctor, Goldstein said. And each additional month without vaccination is a month without protection — both for the child and others.

"If you're postponing vaccination, not only are you putting your children at risk, you're putting the community at risk," he said.

Goldstein, who has consulted for Merck on its vaccine against the cancer-causing human papillomavirus, collaborated on the study with Drexel colleague Jonathan Purtle and Joanna S. Suder, a Delaware deputy attorney general with expertise in public health issues.

Goldstein said he was at a loss to explain why New Jersey had such a high number of proposals to weaken vaccine protections. Most were sponsored by Republicans, but it was a bipartisan phenomenon.

For example, Sen. Shirley Turner, a Democrat who represents parts of Mercer and Hunterdon Counties, introduced legislation three times during that period that would allow students to skip vaccines if they conflicted with the child's or parents' "personal, philosophical or moral belief."

The state allows exemptions only on medical or religious grounds, and Turner's proposal, like Schepisi's, did not progress in the Legislature.

In response to questions about the bill, Turner's chief of staff, Meredith Rivera, said the politician was out of town and not available to speak. The senator introduced the bill after hearing from constituents who were "concerned about the frequency and timing of vaccines" and wanted New Jersey to join other states that allow philosophical exemptions, Rivera said.