CNN  — 

Fainy Sukenik believes in vaccines, and her four children are up to date on all their shots.

That’s why she’s furious that her baby got measles. Too young to be vaccinated, 8-month-old Shira Goldschmidt developed complications from the virus and had to be hospitalized.

Infectious disease experts say the cause is clear: anti-vaxers.

Both in the United States and in Israel, where Sukenik lives, the ongoing measles outbreaks started with pockets of people who refuse to vaccinate their children. Those anti-vaxers can then spread measles to babies outside their communities because even if parents want to vaccinate their children, babies don’t get their first measles shot until their first birthday.

“I’m so angry and so frustrated,” Sukenik said. “On Facebook, I wrote to the anti-vaxers, ‘you are hurting our kids because of your choice.’ ”

Infectious disease experts say this same scenario is bound to happen in the United States too and may have happened already: Anti-vaxers who’ve chosen not to vaccinate will spread measles to babies under age 1 whose parents want to vaccinate them but can’t because they’re too young.

“It’s absolutely inevitable,” said Dr. Peter Hotez, a vaccine scientist at the Baylor College of Medicine in Houston.