Washington DC - One in six American parents has delayed or skipped some or all of the standard childhood vaccines, according to a new Washington Post poll released Monday.

Most of those parents cite concerns about potential side effects as well as a lack of confidence in the federal health authorities to ensure their safety.

Some 9% have opted out of administering their kids with polio or MMR (measles, mumps, rubella) shots, a trend public health experts warn risks triggering a widespread return of those potentially fatal illnesses that routine childhood vaccination had largely wiped out.

In 2025, the US experienced its worst measles outbreak in more than 30 years, with more than 1,400 total confirmed cases and three deaths, including two young children.

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The people who said they delayed or skipped vaccines were more likely to identify as Republican, be under 35, cite religious beliefs, or homeschool their child.

The wide-ranging Washington Post-KFF poll said parents are even less likely to have vaccinated their children against Covid-19 or the flu: about half of parents did not get their children flu shots last year, and 56% said they were not confident that Covid-19 vaccines are safe for kids.

The vast majority of American parents still support vaccinations and 81% said public schools should still require measles and polio shots, the poll showed.

While vaccinations have long been part of standard-issue medical care, resistance has mushroomed in the US in recent years, stoked in large part by debunked and anti-scientific claims linking shots to autism.

Health and Human Services Secretary Robert F. Kennedy Jr. has played a significant role in fueling those fears by repeating the false claims.

Confidence in the Centers for Disease Control and Prevention along with the Food and Drug Administration was split: 51% of those polled said they're not convinced those federal bodies can ensure the safety and effectiveness of vaccines.

As the top US health official, Kennedy has taken steps to curb access to Covid shots and recently ousted the CDC director Sue Monarez over immunization guidelines.

That move helped spur California, Washington and Oregon to announce the formation of a "West Coast Health Alliance" that will work with scientists and medical associations to craft its own recommendations.

Monarez is set to testify before the Senate health committee this week.

RFK Jr.'s revised Advisory Committee on Immunization Practices – an advisory board meant to make recommendations to the CDC, which he has staffed with vaccine skeptics – is also set to convene at the end of this week.