Training physicians in communication skills may not make it any easier for them to convince vaccine-resistant parents to inoculate their babies, a study suggests.

Researchers invited physicians at 30 clinics in Washington state to attend 45-minute classes led by a pediatric immunization expert and health educator. But doctors who attended the sessions were no better at lowering vaccine resistance than their colleagues at 26 other clinics where training wasn’t offered.

“It’s possible that a longer, higher-intensity version of the training might be more effective,” lead study author Nora Henrikson, a specialist in patient behavior at Group Health Research Institute in Seattle, said by email.

On average, about 95 percent of children in most states are up to date on the recommended childhood vaccinations against diseases including measles, mumps, rubella, tetanus and pertussis, according to the U.S. Centers for Disease Control and Prevention.

But clusters of much lower vaccination rates in certain communities, driven in large part by parents’ resistance to inoculation, leave some members of those communities vulnerable to serious and potentially fatal illnesses, according to the CDC.

To understand how parents felt about vaccination in Washington state, Henrikson and colleagues reached out to mothers of newborns at four hospitals in two counties, inviting them to participate in the study if their babies had no medical complications and they planned to receive routine well-child care from a clinic participating in the study.

Researchers spoke to 347 mothers about their perception of vaccines once when the babies were 4 to 6 weeks old and again six months later.

In the months between interviews with the mothers, researchers offered communications training to some of the physicians treating their babies.

The training classes emphasized the importance of establishing trust with families to improve vaccination rates, and participants also received access to additional web-based training, monthly email reminders on communication strategies and handouts for parents explaining the value of vaccines.

At the start of the study, about 11 percent of the mothers were hesitant about vaccinating their babies, and 2 percent of them were extremely resistant.

Among women who took their babies to pediatricians who received training, vaccine resistance dropped from 9.8 percent at the start of the study to 7.5 percent six months later.

When doctors didn’t receive training, the mothers’ resistance dropped from 12.6 percent initially to 8 percent at the end of the study.

One limitation of the study is that not all clinics that agreed to participate saw mothers who also enrolled in the trial. Also, many doctors and parents who initially agreed to help with the experiment failed to complete all the surveys.

It’s also possible that the training didn’t appear very effective because the number of mothers who were resistant to vaccines at the start of the study was lower than expected, Henrikson said.

Doctors who need to improve their communication skills may also need more than a single class to accomplish this goal, said Julie Leask, a public health researcher at the University of Sydney, New South Wales in Australia, who wrote an editorial accompanying the study in the journal Pediatrics.

Moreover, the physicians who choose to attend extra training sessions may very well be the ones who already have decent communications skills, leaving less room for improvement, she said.

“Only two thirds of the doctors actually attended the training, and the session was pragmatically brief to fit in with the realities of busy clinicians,” Leask said by email.

“We need to be very careful in not abandoning an intervention that may have not been delivered to enough people in enough of a dose.”