The number of measles(はしか)cases in the US has reached its highest point in more than a decade, a trend that is largely the result of parents refusing vaccinations for their children. Recent questions regarding vaccine safety and links to autism(自閉症)have led many parents to leave their children unvaccinated. While the number of cases remains relatively small, just 131 so far, there were only 42 cases reported in all of 2007. Health officials insist that the vaccinations are safe and that there is no strong scientific evidence linking either the measles vaccine or a mercury-based preservative(防腐剤)once commonly used in vaccines to autism.