In a surprise twist, authors here retracted findings of a study that found N95 respirators were better than surgical masks at preventing flu.

After a re-analysis prompted by questions from reviewers, the findings were no longer significant, said Holly Seale of the University of New South Wales in Sydney, Australia.

The original study, presented earlier this year, formed the basis of several important policy decisions, including Centers for Disease Control and Prevention guidance on the use of masks in a health care setting.

The retraction — near the end of a presentation at the annual meeting of the Infectious Diseases Society of America — prompted a “rush to the microphones” by those involved in flu prevention, one expert said.

The findings appeared to differ — not only from previous reports, but also from the abstract submitted to this meeting, said Dr. Andrew Pavia of the University of Utah.

Seale acknowledged those differences and agreed that the original results no longer stand. She was not immediately available for additional comment.

The lead author of the study, Raina MacIntyre, also of the University of New South Wales, did not attend the meeting here.

The retraction took experts here by surprise, although many had been critical of some statistical aspects of the study, according to Dr. Neil Fishman of the University of Pennsylvania.

“I think there was little bit of shock that there was such a large change (in the results),” he told MedPage Today after the session.

The study was first presented in San Francisco earlier this year and led to important policy decisions in the United States.

Among other things, it influenced an Institute of Medicine recommendation that health care workers caring for flu patients should use the more expensive N95 respirators.

When Cathlene Echan walked into her pediatrician’s office two weeks after giving birth, she was nervous about discussing her recent decision not to vaccinate her second baby.

But Echan, of Orange County, Calif., did not expect to be asked to leave.

“The doctor said it was too much of a liability to have us as patients,” said Echan, a 28-year-old stay at home mom. Echan’s oldest child, Josiah, now 5, had just been diagnosed with autism around the same time her second son Torren, now 2, was born.

Echan said she did research and read articles online about autism, she talked with other parents and then came to the pediatrician’s office with doubts about vaccines.

“I hadn’t come to a conclusion at that point when I saw the doctor, but I was so nervous because they’re brothers, and I thought there could be a predisposition for it,” said Echan. “As a mom, I can’t knowingly do something to my second child when I believe it played a role in causing my older child’s neurological disorder.

“She was very nice at first, but when I asked her to give him [Torren] a checkup, she said, ‘you need to leave,’” said Echan.

Echan’s situation is a growing problem for parents and pediatricians alike. Despite adamant statements from the American Academy of Pediatrics and the U.S. Centers of Disease Control that vaccines have no link to autism, an anti-vaccination movement is growing online, from parent to parent, and through activist celebrities, such as actress Jenny McCarthy.

Now, more and more doctors are feeling compelled to say “no” back to these parents. The issue was raised Wednesday at the annual American Academy of Pediatrics meeting in Washington, D.C.

Dr. Gary Marshall, a presenter at the meeting, said there are some cases when it’s ethical and legal to refuse to continue to see, or treat, a child.

“In the middle of treatment, you can’t just say, I’m done,” Marshall, of the University of Louisville School of Medicine, said during a session that addressed parental concerns about vaccinations and how pediatricians can respond.