Massachusetts health officials are preparing to immunize most of the over 500,000 children ages 5 to 11 against the COVID-19 virus as soon as federal regulators grant emergency approval to the Pfizer vaccine.

Secretary of Health and Human Services Marylou Sudders told a legislative oversight panel Thursday the Baker administration expects approval of the vaccine for younger children sometime in the first week of November and will deliver the shots to pediatricians, school-based clinics, local boards of health and other providers.

"We are getting ready. We expect that the vaccines will be arriving between October 26 and no later than November 5th," Sudders said.

Department of Public Health commissioner Margaret Cook told a joint of several legislative committees the state has placed an initial order of 360,000 doses of vaccine on behalf of 289 providers.

"We have, as the Secretary said, been able to preorder child vaccine from the federal government, and obviously, we think this is a strong sign that they are confident that it will be approved for 5 to 11 year olds," Cook told lawmakers.

Shots will be available through school-based clinics like the ones currently serving students over 12 years old, from pediatricians, local health boards, other providers and through some retail pharmacies.

The initial order will be enough to vaccinate about 70 percent of the state's children in the 5-11 age range.

Elementary and Secondary Education Commissioner Jeffrey Riley told the panel school districts will be prepared to send out notices to parents about vaccine availability. Riley said schools will have the option of opening vaccination clinics on school property the same way middle and high schools have been offering the shots since the spring.