Giving the second shot soon after the first aligns with what some other countries, such as Germany, the United Kingdom and France, recommend – and the US Centers for Disease Control and Prevention (CDC) also says it’s an option.

“More parents have heard about doing it ‘early’,” said Elias Kass, a naturopathic physician and vaccine advocate in Seattle, Washington. The CDC typically recommends giving the first MMR shot after age one and the second between the ages of four and six. But Kass began recommending the MMRV shot, which combines the second MMR and chickenpox (varicella) into one, at 15 months of age when measles cases began increasing a few years ago.