Adult vaccinations key to preventing future epidemic
EVERETT - Public health officials may never know exactly how the ongoing whooping cough outbreak began, but two contributing factors are known in Snohomish County: most adults are not vaccinated or unaware of the adult vaccine and a higher-than-average number of parents are choosing not to vaccinate their children.
Snohomish County is at the epicenter of the pertussis outbreak, commonly known as whooping cough. The county had the highest per capita rate of whooping cough cases last year with 226. This year’s count is at 137 as of last week. A large number of the cases were among children aged 5 to 17, with 98 cases reported among that age group.
Cases of whooping cough continue to rise as health officials keep urging adults to get vaccinated.
The adult vaccine, called Tdap (tetanus, diphtheria and pertussis) is a relatively new vaccine. Many adults are unaware of it or may think the standard tetanus shot they got covers pertussis.
Snohomish County also is one of a few counties with a higher-than-average number of parents opting not to vaccinate their children before they enter kindergarten.
“I think they are definitely one of the things contributing — not the only thing. Pertussis is common,” state Department of Health immunization program spokeswoman Michele Roberts said last week.
In Snohomish County, 92 percent of kindergartners had a mandated pertussis vaccine in the 2009-2010 school year, the latest figures available from the Department of Health show.
Health officials say a 95 percent public vaccination rate is needed to prevent an outbreak of pertussis.
Pertussis can be harmful to adults, but deadly to infants who are too young to be vaccinated. A Lake Stevens infant died last year from pertussis; the death was one of two in the state.
Health officials are pushing adults to get vaccinated on the premise mass immunization will prevent a future epidemic. Last fall, county health officials declared the pertussis outbreak an epidemic.
Pertussis cases naturally ebb and flow — there is an outbreak every three to five years, Roberts said.
Nationally, less than 10 percent of the adult population is vaccinated against pertussis. 
In Snohomish County, the Snohomish Health District estimates 450,000 adults are not vaccinated, district communicable diseases director Tim McDonald said.
Many people do not know their immunization history and some assume the tetanus shot they got includes the pertussis vaccine, Group Health spokeswoman Katie McCarthy said last week.
McDonald passionately urges adults to get vaccinated for the safety of children.
This year, two infants from Monroe and one adult from Lake Stevens have been hospitalized, the health district reported.
Childhood vaccinations for pertussis wane after five years, which is why health officials want adults to get the Tdap shot. Because Tdap is so new, the science isn’t settled as to whether it lasts for life.
The Snohomish Health District reports there have been 137 cases this year as of last week and estimates the county is on track to top 2011 figures.
The district recently has been organizing free vaccination clinics.
At free vaccination clinics held Feb. 4 and Feb. 25 in Everett, a combined more than 750 adults received Tdap shots.
Group Health’s clinic is seeing more people coming in to get pertussis vaccines also, McCarthy said.
The district is working on holding free vaccine clinics in the east and north county, but the next ones are not firmed up yet, McDonald said.
The north county and east county have been hardest hit with pertussis cases. Marysville, Lake Stevens, Arlington and Stanwood top the list of local cases as of Feb. 17.
Snohomish has had eight cases, including a series of cases in the Snohomish School District in mid-February. Five students were reported to have pertussis.
Mukilteo stands at eight; Monroe, three; Everett, three.
Officials don’t know why Everett’s per-capita rate is so low because, as an urban population, highly communicable diseases like whooping cough can spread fast, McDonald said.
Officials are quick to point out there is no way to trace where the outbreak started or who caused it.
“There is a level of pertussis circulating at all times, and sometimes we see outbreaks like what’s happening in Snohomish County,” Roberts said.
The state is on track to eclipse 1,000 cases by year’s end, Roberts said.
The statewide high was 1,026 cases during a 2005 epidemic.
The overall trend for a normal year of cases, though, is much higher now compared to the 1980s. During an abnormally high case load in 1984, 326 cases were reported.
Neither McDonald nor Roberts can pinpoint why the trend went up.
Exemptions
The trend among parents not to vaccinate their children rose in the past 12 years. By last year, the state has one of the highest exemption rates in the country.
A rising number of parents are becoming leery of vaccinating their kids, and health officials are aware of this. Some parents may be basing their decisions on inaccurate information, Roberts said.
“They want to understand what they’re choosing for their child,” Roberts said.
At the same time, the state is requiring a larger set of vaccinations for children that adults never had to receive, such as for chicken pox, adding to parents’ skepticism, Roberts said.
The state allows parents to opt out of immunizing their children based on religious and medical reasons. Until 2011, it allowed parents to opt out because of certain philosophical reasons, Roberts said. In 1998, only 3 percent of parents exempted their children from vaccinations. In 2010, the figure gradually rose to 6 percent.
Health officials found some parents were exempting their children on philosophical grounds as a convenient way to skip providing vaccination records to schools, Roberts said.
To address that, the Legislature changed the law last year to require parents to get a “Certificate of Exemption” from a medical provider.

By MICHAEL WHITNEY
Published March 7, 2012