Pertussis, a respiratory illness particularly dangerous for infants, is circulating in Washington at a higher rate than last year, and some people in the community are worried that Vashon is at risk of a whooping cough outbreak.

The risk is not simply about the number of cases circulating, however, but about how well people on Vashon are immunized against the disease. Those numbers, according to school district nurse Kate Packard, do not look good.

For several years, a high number of parents have chosen not to vaccinate their children, and this year the percent of enrolled students not fully vaccinated has increased slightly, Packard said. At Chautauqua Ele-mentary School, only 85 percent of children are immunized against pertussis. This is particularly worrisome for health officials, because herd immunity — the number of immunized people necessary to stop disease from spreading if it enters a community — is roughly 90 percent for pertussis. 

“I think we have a very strong possibility of having an outbreak this spring or next fall,” Packard said. 

At Public Health-Seattle King County, Dr. Jeff Duchin, the head of Communicable Disease Control, said it is difficult to accurately predict the timing of a pertussis outbreak in any community, but he agrees with Packard that Vashon is under-immunized and at risk of an outbreak. 

“If you continue to stand on the train tracks long enough, the train is going to come,” he said.

Pertussis, a highly contagious bacterial disease, might cause a prolonged respiratory infection in older children and adults, but in babies, the illness is more severe, with increased hospitalizations and deaths.

From the beginning of this year to March 19, Washington had 75 reported cases of whooping cough in contrast to 29 at the same time last year, according to Michele Roberts, the immunization program manager at the state Department of Health. Twelve of this year’s cases have been in babies under 1, with two infants younger than three months old hospitalized.

So far this year, Pierce County has reported 18 cases, Snohomish County 28 cases and King County only four cases.

But the reported cases, Roberts said, are just the tip of the iceberg because of the nature of the illness. It is possible for adults to have it and not know they are sick in a serious way. In fact, Roberts said, the majority of babies contract pertussis from a parent, oftentimes without the parent knowing he or she has whooping cough.

Despite the increase in cases across the state, the number is still in the normal range, Roberts said.

Typically, pertussis follows a three- to five-year cycle of waxing and waning, Duchin said, and while vaccination has brought the overall number of cases down, the overall incidence of the disease still follows the same roller coaster pattern as part of its natural cycle. 

Pertussis will never be eradicated, Duchin said, but because it poses such severe risks to infants, public healthy professionals say it is extremely important that community members who can be immunized against the disease do so. This includes older children when it is time for the pertussis booster — around age 11 — as well as adults, since immunity from the vaccine wears off over time.

On Vashon, however, it is not just pertussis that worries school district officials, but other diseases as well, including measles — also a  highly communicable disease that can have serious health consequences.

“Measles can be a devastating disease,” said Packard, who endured the disease as a child.

The percent of Chautauqua families vaccinating against measles continues to hover at 83. This is troublesome to Packard, in part because herd immunity for measles is between 83 and 94 percent. 

Also of note at Chautauqua this year, Packard said, is that 13 percent of entering kindergartners are not vaccinated at all. This is in contrast to previous years, when about 10 percent of kindergarten families filed exemptions for all the vaccines.

As a result, school district officials have recently begun attaching new information to the exemption form that all parents seeking vaccine exemptions must sign.

The information — written by Dr. William Foege, a global health expert who devised the strategy to eradicate smallpox and a Vashon resident concerned about the Island’s low vaccination rates — calls on those who opt not to immunize their children to understand the implications of their decision. 

“I recognize I am able to make this choice because the risk of acquiring these diseases is reduced by the fact that other children have been immunized,” the new form reads in part. 

“I also realize that if my child gets one of the diseases listed, that they provide a risk to other children at school, in the doctor’s office and the community,” it continues. “I also realize that if my child gets rubella, she or he will be a risk to the unborn child of a pregnant woman, and if my child gets pertussis, he or she will be a risk to infants who cannot receive the first dose of vaccine until they are two months old.”

Concern about low vaccination rates is not just occurring on Vashon, but at the state level as well. A measure in the Legislature would require parents who wish to be exempt from vaccination laws to provide a signed note from a physician, stating they have discussed the risks and benefits of immunization. According to a recent Seattle Times story, Washington has one of the highest exemption rates in the country. Recently, more than 100 people went to Olympia to protest the proposed law.

On Vashon, this topic will be up for discussion at the next Vashon School District Community Dinner, scheduled for Tuesday, April 12, at the high school. 

Celina Yarkin, a farmer and mother of three who last year created an informational display about vaccines, will bring her updated board and will speak about pertussis and the low vaccination rates here. It is a hard topic, one where passions run high, she said, because people are making choices about the best ways to protect their families. But it is also about community immunity, she noted, which is why she decided to get involved in the debate.

Vaccinations, she said, are “one of the few really useful tools we have to protect ourselves and others from diseases that people used to be really afraid of. … It’s about all of us protecting each other.”