A spike in the number of measles cases in Hawaii last year, coupled with the fact that the percentage of unvaccinated kindergartners has doubled over the past decade, serves as an urgent warning that the islands are not immune to the kind of outbreaks that have sickened hundreds of people in the continental United States.

The state Department of Health must be supported in redoubling its efforts to promote the immunization of all eligible children and adults, a medically sound, socially responsible message that requires continual reinforcement in an Internet era that allows misinformation to persist long after it has been debunked — as in the case of a fraudulent British study falsely linking measles vaccines to autism.

Caring communities committed to advancing public health should not willfully expose their most vulnerable members to a miserable, highly contagious, vaccine-preventable infectious disease that only 15 years ago was considered eradicated in the United States. There should be no pussyfooting around those facts as health officials, and the state and county officials who help determine funding for their work, strive to prevent measles from regaining a firm foothold in Hawaii.

According to the U.S. Centers for Disease Control, "research shows that people who refuse vaccines tend to group together in communities. When measles gets into communities with pockets of unvaccinated people, outbreaks are more likely to occur. These communities make it difficult to control the spread of the disease and make us vulnerable to having the virus re-establish itself in our country."

That’s the risk of a troubling state trend that is especially obvious on Kauai, where the parents of 8.3 percent of the children entering kindergarten for the 2013-14 school year refused to immunize their children for religious reasons, more than four times the statewide exemption rate of 2.1 percent.

Even more alarming than the raw numbers are the trend lines, and not only on Kauai. The percentage of unvaccinated kindergartners has risen sharply in every Hawaii county over the past decade.

The religious exemption rate has more than quadrupled on Oahu (from 0.2 percent to 0.9 percent), more than doubled on Kauai (from 4.1 percent) and Maui County (from 2 percent to 4.3 percent), and also risen in Hawaii County, from 2.4 percent to 3.7 percent.

Although the exemption rate is lowest on Oahu, that’s also where the largest population of vulnerable kindergartners reside, so this issue should not be dismissed as a neighbor island problem.

Hawaii law allows parents to seek an exemption for their children from schools’ immunization requirements on medical and religious grounds. However, the exemption does not preserve the unimmunized child’s right to attend school no matter what.

Inadequately immunized students shall be excluded from school whenever "there is the danger or presence of an outbreak or epidemic from any of the communicable diseases for which immunization is required."

This rule is both necessary and fair, and should be vigorously enforced to protect the public health. Parents are not forced to have their children vaccinated, but neither are they allowed to impose their views on the rest of the school community when the risk that their child will catch and spread the disease rises.

After three years with no reported measles cases, Hawaii logged 15 cases last year, seven of which occurred on Kauai. All 19 cases over the past five years occurred when traveling Hawaii residents caught the measles outside the state, brought it home and infected others, health officials said.

Although Hawaii’s overall immunization rate remains high, the trend for childhood vaccinations is headed in the wrong direction.

We need as rapid and comprehensive a public health response to this troubling trend as we would to an actual measles outbreak.