A new study has found that the Pfizer COVID-19 vaccine is less effective at protecting children from the omicron variant.

Researchers with the New York State Department of Health found that the vaccine's effectiveness dropped from 68% to 12% in children aged 5 through 11 between Dec. 13 through Jan. 24.

But the Centers for Disease Control and Prevention issued a report on Tuesday that stated the vaccine effectiveness in children between the ages of 5 and 11 after its second dose was 46%.

"Two doses protect against COVID-19–associated emergency department and urgent care encounters among children and adolescents," the CDC report said. "However, vaccine effectiveness (VE) was lower during omicron predominance and decreased with time since vaccination."

The public health officials who conducted the study believe it may be due to the lower dosage they received.

Kids in that age group were given 10 milligrams, while anyone over 12 received 30 milligrams.

The study also found that the effectiveness in children ages 12 to 17 dropped from 66% to 51%.

The study results come as New York City is set to end its mask mandate on March 7, CNBC reported.

Last week, the Centers for Disease Control and Prevention eased its masking guidelines.