SEATTLE – Students attending hundreds of schools in the state of Washington could face an increased risk of contracting some preventable diseases because immunization completion rates aren't high enough to protect them in the event of an outbreak, a KING 5 analysis of statewide vaccination rates found.
Each year, the majority off Washington kindergarten students get the required vaccines, but public health officials say they become concerned when they notice large numbers of un-immunized students clustered together in school settings. The science is clear that the choice parents make to vaccinate or not to vaccinate their children can affect the entire community – all because of a sheltering effect called "herd immunity."
It's the percentage of people who must be vaccinated for a disease in order to protect the people who aren't vaccinated from getting sick. Every disease has it's own herd immunity threshold. To prevent the spread of measles, for example, 83 to 94 percent of a community must be vaccinated, according to the National Institute of Allergy and Infectious Disease.
Because nearly all students have to be vaccinated to effectively prevent the spread of most diseases, the state set a goal for all Washington schools to have 95 percent of their kindergarten students complete all immunizations. But statewide, most schools have consistently failed to meet that target each year, according to a KING 5 review of annual vaccination data reported to the Washington Department of Health between 1988 and 2017.
"What that means is there's an opportunity for us to prevent more illnesses, missed days of school, doctors visits and hospitalizations by maximizing the number of students who are in compliance with school immunizations," said Jeff Duchin, the public health officer for Seattle and King County.
The KING 5 analysis of the school-reported data also revealed:
- Just 258 schools of the 1,425 Washington schools that reported vaccination data last school year reached or exceeded the 95 percent state target.
- Nearly half of Washington schools that reported kindergarten immunization data last school year had completion rates too low to effectively prevent the spread of pertussis, also known as whooping cough, in the event of an outbreak. Hundreds of schools fell below the herd immunity levels for other diseases, too, like measles and rubella.
- Most parents who choose to excuse their children from some or all vaccinations get a certificate of exemption for "personal" reasons.