New federal data show more Maine parents are choosing not to vaccinate their children, a trend that worries health providers as an outbreak of whooping cough continues to worsen and students prepare to go back to school.

Vaccines are crucial to sparing both children and adults from whooping cough and other dangerous and preventable diseases, said Dr. Michael Ross of Husson Pediatrics in Bangor.

“Lack of their use leads to outbreaks like this,” he said.

Maine has recorded 411 cases of whooping cough this year, nearly five times the number of cases reported at this time in 2011. Most cases of the highly contagious disease have struck children ages 7-19. Within that group, two out of every 1,000 children ages 7-10 have been diagnosed with whooping cough in Maine this year.

The outbreak ranks Maine among the top 10 states in the nation for the incidence of whooping cough, or pertussis, according to the federal Centers for Disease Control and Prevention.

Whooping cough, which can spread through the coughing and sneezing of an infected person, has touched every county in the state. Cumberland, Somerset, Penobscot and Androscoggin counties have been hit the hardest.

The rise in Maine mirrors a nationwide trend. Washington state has declared an epidemic of whooping cough with more than 3,500 cases this year. The disease has been blamed for 13 deaths in the United States in 2012, mostly among infants under 3 months old.

Meanwhile, new federal CDC data show Maine tied with Hawaii and Arkansas at 10th in the country for parents exempting their kindergarteners from vaccinations. Health officials say that’s one factor in Maine’s whooping cough outbreak this year, stressing that it’s just as important for older kids and adults to stay up to date on their shots.

In the 2011-2012 school year, 517 children enrolled in Maine public and private kindergarten classes were exempted by their parents from at least one vaccine, according to data released Thursday by the national CDC.

That translates to an exemption rate of 3.9 percent among kindergarteners in Maine, an uptick from 3.3 percent in the 2009-2010 school year.

Most parents cited “philosophical” reasons for shielding their kids from shots. Maine is among 18 states that allow parents to exempt their children from school-required immunizations based on philosophical objections. Parents also may claim medical and religious reasons.

Parents who skip vaccines say they object to the number of shots and fear a link between immunization and autism, according to a 2008 report by the Muskie School of Public Service.

Worries about vaccines contributing to autism, a theory that has been discredited by research studies, have since diminished some, said Caroline Zimmerman, staff coordinator for the Maine Immunization Coalition, a collection of health care providers, consumers, drug companies and others working to reduce vaccine-preventable disease.

A widely publicized study published in a British medical journal that linked the measles, mumps and rubella vaccine to autism later was deemed fraudulent.

But some parents are hesitant to see their infants and young children stuck with needles numerous times, and say not enough research has been done into the cumulative health effects of so many shots.

“We’ve heard from providers that the number of shots has been a concern for parents,” Zimmerman said.

Without an exemption, kindergarten students in Maine must be vaccinated against pertussis, diphtheria, tetanus, measles, mumps, rubella, polio and chickenpox.

“It doesn’t harm the child at all,” Zimmerman said. “They’re very resilient, it doesn’t overload them to get three or four shots in one session.”

Some parents who are worried about the number of needle sticks choose to spread their children’s immunizations out over a longer period, but vaccines are purposefully timed to be administered when children are at most risk for certain diseases, she said.

“The on-time [vaccination] is important because you’re keeping kids protected at a time when they need it the most,” Zimmerman said.

Maine’s exemption rate is a sign that health providers need to do a better job of educating the public about vaccine safety and effectiveness, as well as understanding parents’ hesitations, she said. Some may not be aware of the risks that skipping or delaying vaccinations poses to their children and to the community, Zimmerman said.

Health officials say children being exempted from immunization by concerned parents is only one contributor to this year’s whooping cough outbreak.

Some children may get an initial shot, but never go back to complete the series. It’s estimated that only 60 percent of children get the required booster shot, which protects against pertussis, diphtheria and tetanus.

“People forget that kids aged 10 to 12 need to get that booster,” said Patty Hamilton, public health director for the city of Bangor.

Health officials also urge anyone who has contact with infants — including pregnant women, parents, grandparents, day care providers and teachers — to get a pertussis booster, or Tdap shot.

Pertussis is dangerous to babies — who don’t typically exhibit the characteristic “whooping” sound as they gasp for air — because it can rob them of oxygen, leading to brain damage and even death.

Medical professionals recommend vaccinating infants against pertussis with a series of shots starting at 2 months of age. Children too young for the shots or who haven’t built up enough immunity often catch the disease from a loved one who was never vaccinated or failed to stay current with booster shots.

All adults are advised to get vaccinated against pertussis with their regular tetanus booster, said Dr. Mark Bouchard, medical director for the Maine Medical Center Family Medicine Centers.

“That’s where pertussis lives, in the adult population, because they haven’t been immunized and they expose kids to pertussis,” he said.

The latest data show that fewer than 10 percent of adults have received a Tdap booster shot.

Some people catch whooping cough despite being immunized. The vaccine wears off over time, but still slashes the risk of catching and spreading the disease and generally leads to a milder case.

Concerns about the vaccine’s waning effectiveness have prompted the national CDC to examine whether to recommend adding another pertussis, diphtheria and tetanus booster to the vaccine schedule, Hamilton said.

While childhood vaccination rates in Maine remain at 93 percent and better, health officials worry about pockets of the state where rates are lower.

Maine should be shooting for 100 percent vaccination, Ross said.

“All it takes is a spark to flare among a number of unvaccinated people for the illnesses to manifest,” he said.

To promote access to immunization, health insurers in Maine and the federal government contribute to a fund administered by the Maine Vaccine Board that pays for free vaccines for all children up to age 19. The vaccines are distributed to health care providers at no cost, but parents may have to pay an administrative fee.

Bouchard expects that program, along with other efforts to boost immunization in Maine, to lead to better vaccination rates in coming years.

Without proper vaccination, whooping cough won’t be the only preventable disease to break out in Maine, Hamilton said.

“Today it’s pertussis, but tomorrow it’s something else,” she said.

Jackie Farwell

I'm the health editor for the Bangor Daily News, a Bangor native, a UMaine grad, and a weekend crossword warrior. I never get sick of writing about Maine people, geeking out over health care data, and...