Suellen Hopfer, assistant professor of public health at UC Irvine, held focus groups with scores of Orange County families to understand their thinking on vaccinating children. Fewer than half — 45% — said they’d get their adolescent children vaccinated. Nearly as many — 43% — were unsure. And 11% said they definitely would not. “The younger the children were, the more hesitant the parents were to have them vaccinated,” Hopfer said.