Colorado was ranked 30th in the country for immunizing children last year, a drop from 16th place in 2005.

The change in ranking came from a dip in the vaccination rate from 83.4 percent in 2005 to 80.3 percent in 2006, according to a Center for Disease Control survey released Thursday.

"This small change in our rate is not statistically significant from last year, even though it had a large impact on our state ranking," said Ned Calonge, chief medical officer with the Colorado Department of Public Health and Environment.

He noted that the CDC survey has a margin of error of 7 percent, and since most of the states in the country have rates near 80 percent, a slight drop of the percentage points would affect the ranking.

Nationally, the immunization rate also dropped slightly, from 80.8 percent in 2005 to 80.6 in 2006.

"Basically, our rate didn't change," Calonge said. "But the percentage point did drop. I would have liked to see them go up, but statistically, we've leveled off. We didn't continue to rise and we want to keep pushing."

Thursday, the Center for Disease Control released the results of their survey of children, between the ages of 19 to 35 months, who have completed all their shots.

Calonge noted that Colorado had made great strides in in getting children vaccinated.

It was only four years ago, 2003, that the state was ranked 50th in the country for immunizing children.