NEW YORK (Reuters Health) - When parents are more knowledgeable about vaccinations, their children are more likely to get them, a new study shows.

The study, which included parents of 630 Spanish children, found that while most children received the recommended vaccinations, parents'

vaccine knowledge influenced the likelihood.

When parents scored below the average on a test of vaccine knowledge, their children were 55 percent to 60 percent less likely to be on schedule with their immunizations, according to findings published in the online journal BMC Public Health.

The findings suggest that if doctors do more to inform parents about vaccine effectiveness and safety, they will be more likely to keep their children on the recommended schedule, according to the researchers, led by Dr. Eva Borras of the Department of Health in Barcelona.

In recent years, there has been growing public concern about vaccine safety -- including a proposed, but unproven, link between the measles-mumps-rubella (MMR) vaccine and autism.

Relatively low vaccination rates have been blamed for the resurgence of measles and mumps in certain European countries.

The current study involved parents of 630 children younger than 3 who were surveyed about their vaccine knowledge -- such as when infants should start routine vaccination; whether vaccine-preventable illnesses are potentially serious; and whether vaccines are "harmful."

The researchers also looked at whether the children were on schedule with their immunizations, including the MMR vaccine; the DTaP vaccine against diphtheria, tetanus and whooping cough; the polio vaccine; and the Hib vaccine, which protects against bacterial meningitis.

In general, the researchers found, the likelihood of a child being on schedule increased along with parents' vaccine knowledge.

About 20 percent of parents said that vaccines could have "undesirable consequences," the study found. Nearly one quarter of those parents could not state a specific risk; another 18 percent cited "adverse reactions," and a similar percentage thought that vaccines cause allergies and asthma.

In general, experts say, the most common side effects of vaccines are short-term fever and mild rash, while serious allergic reactions are rare. The MMR vaccine, for example, causes a severe reaction in less than one per 1 million doses, according to the U.S. Centers for Disease Control and Prevention.

Borras told Reuters Health that parents who are concerned about vaccine safety should bring their questions to their pediatrician -- rather than relying on advice from friends or information online.

She also said that doctors need to be aware of shifting public attitudes toward vaccination and bring up the issue with parents.

SOURCE: BMC Public Health, online May 27, 2009.