NEW YORK (Reuters) - Chris Barr had no problem getting his eight children exempted from vaccinations when they went to school. First in California, and later when the family moved to Arkansas, the natural healing practitioner simply signed a piece of paper stating that his personal beliefs didn’t allow the immunizations.

Such exclusions may not be so easy to obtain going forward. This year’s highly publicized measles outbreaks, which have infected more than 150 people in 17 states, are no longer front page news. But they could well have a lasting public health legacy. Already, lawmakers in at least 10 states are promoting legislation that would make exemptions far harder to obtain.

The proposed laws have been introduced in statehouses by both Democrats and Republicans and include a range of approaches, from requiring schools to post immunization rates to entirely eliminating religious and philosophical exemptions. But they all respond to one undeniable fact: Most of the recent measles cases have been in people who were not vaccinated against the disease.

Lawmakers say they are optimistic about the chances of the bills, though most of them aren't far enough along in the pipeline to predict their fate. Many of the authors say the extensive coverage this year has helped their case.

Legislators also say the laws they are proposing have received bipartisan support and that they are likely to survive consideration by legislative committees and be voted on in the coming weeks and months. In eight states, Democrats introduced the legislation, while in Texas and Vermont bills have been proposed by Republicans.

“This is not the last outbreak we’re going to see,” said Washington Rep. June Robinson (D). “The issue will continue to be in the public conversation.”

The year’s largest measles outbreak has been traced to Disneyland in Anaheim, California where visitors were exposed to the disease in mid-December. The vast majority of cases have been in that state, which allows both philosophical and religious exemptions.

In all, 10 of the 17 states with reported measles cases have allowed parents to opt out of vaccines on philosophical grounds, creating a far easier way out of immunizations than states that only exempt families with extensively documented religious objections or health conditions that preclude vaccinations. Six of the 10 affected states with easy opt-out laws have proposed new legislation.

Oregon and Washington have already held hearings on the proposed laws. But in most other states, bills have only recently been introduced or have yet to be scheduled for committee hearings.

While nearly 80 percent of Americans believe all children should receive vaccinations, according to a Reuters/Ipsos poll, the proposed laws have mobilized a small but vocal community of anti-vaccine advocates who say parents should decide whether their children receive immunizations. Some of the so-called "anti-vaxers" fear vaccines may cause autism, a link scientists say has been thoroughly debunked. Others say they oppose government intrusion in parental decisions.

Several parents opposed to vaccinations testified at the Oregon and Washington hearings and larger numbers showed up last month at a Texas town hall where Rep. Jason Villalba (R) discussed a bill he introduced that would eliminate personal belief exemptions.

In the past, local and national anti-vaccine organizations have successfully thwarted legal efforts to curb exemptions through grassroots efforts. Anti-vaxers quickly mobilized when Colorado, which permits personal and religious exemptions, introduced a measure last year that would require parents to complete an online module about immunizations or consult with a doctor before opting out. The bill passed the state’s House of Representatives but failed in the Senate after parents lobbied and testified in hearings.

The National Vaccine Information Center, a non-profit with 37,000 subscribers to a portal that monitors all legislation concerning vaccines, has urged its members to raise their voices against this year’s crop of proposed laws, which they say could be a tougher fight because of the attention the measles outbreak has received.

“It’s about respecting everybody’s lives,” said Barbara Lowe Fisher, the group’s co-founder and president.

LEGAL IMPEDIMENTS

In some states with easy exemption rules, decades-old court decisions will make changing the laws difficult, if not impossible.

In Maryland, for example, the state’s Supreme Court ruled in 1982 that schools could not deny exemptions to parents with religious objections, saying that could lead to discrimination. The state does, however, have a law mandating vaccines in the case of a public health emergency. Courts in other states have decided vaccination cases differently.

In 1979, for example, Mississippi’s Supreme Court upheld a vaccination requirement for school enrollment, holding that exemptions, including religious ones, put children at risk. Mississippi lawmakers have re-introduced legislation this year that would allow philosophical exemptions, but those efforts have been shot down several times in the past.

Health officials and local representatives said they worry that allowing nonmedical exemptions means that some parents opt out simply because it's easier.

In Idaho, for example, many parents sign a personal belief waiver simply because the school has pointed out that a child is missing a required vaccine, said Tom Shanahan, public information officer for the Idaho Department of Health.

Less than 1 percent of children in the state have received no vaccines at all, Shanahan said, but there is a 6.3 percent exemption rate across the state for one or more immunizations. Parents can use a waiver to exempt their child from some vaccinations or all of them. Idaho has not introduced legislation this year that would limit exemptions because “there’s a pretty strong culture of individual rights,” Shanahan said.

And even if they are passed, stronger laws may not convince parents who oppose vaccines to immunize their children.

One pediatric nurse practitioner, who requested anonymity for fear of retribution at work, said she has decided to home-school her four-year-old son after a Brooklyn school denied her repeated appeals to exempt him from his hepatitis B and flu shots.

"It's completely unfair and it's ridiculous and a violation of the Constitution," the nurse practitioner said.

For a graphic examining measles cases in the United States go to: http://graphics.thomsonreuters.com/15/measles/index.html

(Reporting By Yasmeen Abutaleb, Editing by Michele Gershberg and Sue Horton)