MONDAY, Jan. 21, 2013 (HealthDay News) -- In recent years, nearly half (49 percent) of U.S. children under the age of 2 did not receive all the recommended vaccinations or received some vaccinations late, a new study shows.
All these children are considered under-vaccinated, according to the Kaiser Permanente researchers who analyzed the immunization records of more than 320,000 children born between 2004 and 2008.
The investigation revealed a significant increase in the number of under-vaccinated children during the study period, and also found that one in eight under-vaccinated children's parents decided not to follow Advisory Committee on Immunization Practices (ACIP) childhood vaccination guidelines, according to a Kaiser news release.
Those decisions meant that children went a longer time between vaccinations or received fewer vaccinations in a single office visit, leaving them under-vaccinated, according to the study published Jan. 21 in the journal JAMA Pediatrics.
The researchers also found that under-vaccinated children are less likely to visit their doctor's offices and more likely to be admitted to hospitals, compared to children who receive vaccinations under the standard ACIP schedule.
"While a large majority of parents in the U.S. choose to vaccinate their children, a growing number of parents are concerned about vaccine safety and choose to vaccinate their children according to alternative immunization schedules," the researchers said in the news release.
"The medical community doesn't have a lot of data on these alternative schedules, so we are hoping the results from this study will open the door to more opportunities to examine their safety and efficacy," they added.
Recent research found that children whose parents refuse to allow childhood vaccinations are nine times more likely to get chickenpox and 23 times more likely to get whooping cough than fully immunized children.
The U.S. Centers for Disease Control and Prevention has more about childhood immunization.