In a week or so, some 75 parents will get letters from the Vashon Island School District informing them that their children either lack documentation that they’ve been fully immunized or lack waivers exempting them from the requirement.

Those families will have 30 days to comply. If they fail to do so, their children can no longer attend Vashon’s public school system.

This may seem like a bold move on the district’s part. In fact, school officials will simply be following the law — and asking that Vashon families follow the law as well.

State law requires that children be immunized to attend school or have in place an exemption spelling out what vaccinations they lack.

Last year, the law was tightened in an effort to ensure that exemptions were based on conviction, not convenience. Now, those who want to exempt their children from immunization requirements have to submit a “certificate of exemption,” signed by a licensed health care provider, indicating that they’ve been informed about the benefits and risks of vaccinations.

It’s no small matter on Vashon, where vaccination rates are far below what health officials believe is necessary to protect those most vulnerable to highly contagious diseases. An analysis by the school district in December showed that 33 percent of the district’s students have not been fully vaccinated against pertussis, or whooping cough, and 22 percent lacked full vaccinations against measles.

To public health advocates, this isn’t simply an issue of personal choice. Those who opt not to vaccinate against diseases like pertussis or measles are putting others at risk. A student can have what he or she thinks is simply a bad cough — and unwittingly infect a baby who could die from pertussis or a pregnant mother who could pass it on to her newborn.

The school district is right to examine this issue and to require families to follow the law. If an outbreak of pertussis were to occur, as some fear could happen on Vashon, those students who are not fully vaccinated would be sent home — not simply for their own protection but to try to contain a disease that could have profound implications on an Island as under-vaccinated as ours.