Massachusetts will launch a new vaccine pre-registration system on Friday for its mass vaccination sites, transitioning away from the single-day bulk appointment drop that for weeks has left residents racing to secure slots.

Bay Staters will be able to fill out an online form with their personal details, contact information and eligibility criteria, then get a notification from the state when they can book an appointment at the mass vaccination site closest to them.

While unveiling the new system, Baker administration officials also announced four dates when mass vaccination sites will administer first doses exclusively to educators and school staff: Saturday, March 27; Saturday, April 3, Saturday, April 10; and Sunday, April 11. Health and Human Services Secretary Marylou Sudders said during a Wednesday morning briefing that the state should be able to administer 20,000 to 25,000 doses to educators and support staff across those four days, depending on federal supply.

This Thursday, one day before the new system begins, will be the final time the Baker administration posts tens of thousands of appointments at mass vaccination sites for the following week. All slots at those locations will start flowing through the pre-registration system on Friday, though eligible residents will still be able to hunt for appointments at local pharmacies, regional sites and through their health care providers.

The new booking platform marks a significant shift in the Baker administration's vaccine rollout after weeks of criticism from lawmakers and residents, particularly aimed at the stress created by jockeying to secure a slot.

"Google Services is working with us to deploy this new pre-registration website that will eliminate the need for people to compete to find appointments throughout the state at the mass vax sites, allow us to pre-register people, and build out a waiting list that will allow us to proactively notify people through text, email or phone," said Secretary of Technology and Security Services Curt Wood.

Gov. Charlie Baker plans to speak about the new program during a Wednesday morning press conference.

Only appointments at the seven mass vaccination sites will be included at first, though the administration said it will work to fold other providers into the pre-registration system starting in April.

Registered participants will receive a confirmation notice and a weekly status update indicating they continue to be pre-registered. At launch, residents will not be able to select preferences for mass vaccination sites and the system will only notify them about appointments at whichever of those sites is geographically closest.

Once slots become available, the state will send a link to book an appointment for the following week. Recipients will have 24 hours to click through and pick their time, and if they do not, they will be placed back in the queue.

Older residents or those who cannot sign up online can call 211 to pre-register and receive notifications by phone.

All residents will be able to pre-register starting some time Friday morning, Wood said, but the administration is encouraging only those who are currently eligible to sign up. The new pre-registration tool will be available at https://www.mass.gov/covid-19-vaccine.

"The system will allow for pre-registration for all. We're messaging that it's only for folks that are eligible to receive the vaccine, so when the appointment notices go out, they will only go out to the folks that are eligible," Wood said. "Those people that choose to jump in line now will have to wait until appointments become available for their criteria."

Wood added that the administration believes the Google-based platform will be "capable of handling all the traffic." The current vaccine appointment website crashed in the face of high volume last month when eligibility expanded to those age 65 to 74.

Officials said eligible pre-registered recipients may need to wait "several weeks" to get notification of open appointment slots given ongoing supply constraints.

Sudders told reporters at Wednesday's briefing that the federal government informed Massachusetts one day earlier that its weekly allocation of about 150,000 first doses will not increase until April.

More than 40,000 new first dose appointments at mass vaccination sites will go live on Thursday in the final round of the existing booking system, she said, and another 40,000-plus second dose appointments have already been scheduled for next week at mass vaccination sites.

This week, the state will send 83,000 doses to mass vaccination sites, 79,000 doses to hospital providers, 38,000 doses to 12 regional collaboratives, 25,000 doses to community health centers, and 25,000 doses to local boards of health in the 20 most impacted communities or in areas where boards need to finish administering second doses.

Another 95,000 first and second doses are being delivered directly to CVS Health sites through the federal pharmacy vaccination program, and 19,000 doses will be delivered by the federal government directly to 15 qualified community health centers.

The state's roughly 400,000 school staff will gain eligibility to book mass vaccination site appointments on Thursday, and any who are unsuccessful can then turn their attention toward pre-registration a day later. Some have already secured slots at pharmacies through a federal program.

Sudders said some of those workers may not receive vaccines until "mid-April" given the limited supply of doses.

Educators had been slotted alongside other essential workers, who do not yet qualify, in the Baker administration's rollout plan, but officials moved them up to follow guidance from the Biden administration.