A boy with cancer just struck a symbolic blow against anti-vaxxers

Just after a school board meeting at his elementary school, 6-year-old Rhett Krawitt made a brief announcement.

"Thank you...for teaching science and making everybody get vaccinated unless they are doing chemo like I did. Soon we will say, 'Gone, measles!'" the Marin Independent Journal reported on Tuesday.

His school board recently voted to support a proposed law that would make vaccinations mandatory for all California students, a goal his father, Carl Krawitt, has been trying to achieve for weeks.

Rhett can't get vaccinated because the chemo he's undergone to treat his leukemia (which is now in remission) has left his immune system vulnerable to infections.

"I respect people's choices about what to do with their kids, but if someone's kid gets sick and gets my kid sick, too, that's a problem," Carl told The New York Times in January.

While the proposal may sound stringent, it's the basis of herd immunity, a concept that's informed over half a century of public health policy and has helped eradicate dozens of once-deadly diseases, from diphtheria and measles to mumps, rubella, polio, and smallpox.

The Krawitt family may have reason to be worried: They live in a part of Northern California where an abnormally high number of parents have refused to vaccinate their kids. Their county of Marin has the highest rate of "personal belief exemptions" (a form parents and a doctor must sign to opt-out of vaccinating their children) in the Bay Area and one of the highest in California.

Carl asked the superintendent of his county's school district Steven Herzog to end the personal belief vaccine exemption in January.

This school year, 6.5% of Marin County children of all ages have the exemption from their parents, a modest drop from last year, since a new law instated in January required parents who file the exemption to have a conversation with their doctor and get their signature before doing so.

At Rhett's elementary school, about 7% of kids are not vaccinated (including those who have the exemption and those who cannot get vaccinated, such as those allergic to a component of the shot), the Times reports.