Vaccination rates among children covered by private health insurers are on the decline and worries about a link between autism and immunizations could be to blame, a new report indicates.

The report, which looked at 2-year-olds covered by more than 1,000 health insurance plans, found that immunization rates dropped by nearly four percentage points for kids insured privately while the rate increased slightly for children on Medicaid between 2008 and 2009.

The findings from the nonprofit National Committee for Quality Assurance are based on vaccination rates for a number of conditions including an immunization for measles, mumps and rubella, which some people believe is linked to autism.

Scientific research has consistently found no connection between the MMR vaccine and autism. However, the report’s authors specifically highlight fears about a link between autism and vaccines — and celebrities promoting this belief — as a possible reason for the decline in vaccination rates among those with private insurance.

“The drop in childhood vaccinations is disturbing because parents are rejecting valuable treatment based on misinformation,” said Margaret E. O’Kane, president of the National Committee for Quality Assurance, which conducted the report.

Last year, 90.6 percent of children covered by private health insurance received the MMR vaccine compared to 93.5 percent in 2008. Meanwhile, 91.2 percent of children on Medicaid received the same immunization last year, up from 90.9 percent the prior year.

The organization says that 85 to 95 percent of the population needs to receive any given vaccine in order to prevent outbreaks.