The American parents who are choosing to skip or delay vaccines for their children are more likely to home-school their children, be White and very religious, identify as Republican or be under 35, according to a wide-ranging Washington Post-KFF poll that sheds new light on what drives vaccine hesitancy.

The poll — the most detailed recent look at the childhood vaccination practices and opinions of American parents — shows that 1 in 6 parents have delayed or skipped some vaccines for their children, excluding for coronavirus or flu. Nine percent have skipped the polio or measles, mumps and rubella (MMR) shots, which public health experts say risks large outbreaks of potentially fatal diseases that have been curbed through widespread vaccination.