The small percentage of Massachusetts House employees who have not complied with a COVID-19 vaccine mandate have three weeks to get on board or face unpaid suspension under a State House reopening update the chamber's leaders rolled out Monday.

All House officers and staff will need to be "available and able to work in person at the State House as a condition of their employment" starting Dec. 13, a House working group wrote in a summary of its new policy.

The shift does not call for a specific number of specific House workers to return underneath the Golden Dome, and decisions about in-person versus remote work will remain "at the scheduling discretion of the employee's supervisor or House HR," officials said.

Representatives will not be subject to the updated in-person rule and will still be able to work and cast votes remotely, according to Speaker Ronald Mariano's office.

While the policy will formally push the House into Phase 2A of its reopening plan, it does not offer any additional insight on welcoming tourists, lobbyists or other members of the public back into the State House more than 20 months after leaders shuttered the building.

"For several months, cases in Massachusetts had plateaued," the working group wrote. "Unfortunately, in recent weeks, infection rates in the Commonwealth and neighboring states have begun to rise again. While the fluid nature of the COVID-19 virus complicates our reopening planning, it is important nevertheless to find a way to progress while prioritizing health and safety."

Vaccine mandate holdouts in the House's workforce are set to face new consequences as a result of the updated policy.

Since the Nov. 1 deadline for the House's vaccine mandate, those who did not comply have been required to continue working from home. But when Dec. 13 arrives, officers and employees who have neither provided proof they are immunized against COVID-19 nor sought an accommodation will no longer have an option to stay remote.

The vaccine mandate the House approved in September, opposed by nearly all of the chamber's Republicans, requires any representative or House employee to submit an attestation or exemption request to work in-person at the State House.

And because all staff must be able to work in-person when needed after Dec. 13, anyone who has not complied with the vaccine mandate by that time will be deemed "unavailable and unable to work in person at the State House," the House working group wrote.

Officers or employees who remain out of compliance as of 5 p.m. on Dec. 13 will be placed on unpaid administrative leave for up to five days or until they come into compliance. Anyone still out of line on Dec. 20 will then be placed on unpaid leave for an additional 10 days, even if they submit vaccination proof or an exemption request during that period.

By Jan. 4, one day before the scheduled start of formal sessions for 2022, employees who still have not complied "will remain on indefinite unpaid administrative leave and may be subject to further disciplinary action."

Workers on unpaid administrative leave will continue to receive health benefits but will not accrue vacation or sick leave time, according to the working group's summary.

Employees will get a five-day grace period to get vaccinated after a request for a religious or medical accommodation is denied.

On Nov. 3, Mariano's office said 98 percent of House employees had either submitted proof of vaccination or requested an exemption from the mandate.

Mariano initially said seven representatives -- who have not been identified publicly -- were not in compliance with the mandate, and his office said Monday that number had dropped to four as of Nov. 9.

In-person work at the State House during Phase 2A will include House sessions, "critical legislative work" and trainings required by House rules, the working group's policy indicates.

The new plan also forecasts a Phase 2B House reopening beginning some time in winter 2022, which the working group said would feature "welcoming larger cohorts of Members, Officers and Employees to work in person at the State House on a more permanent basis."

Many government agencies and bodies have embraced vaccine mandates as a tool to increase immunization against the highly infectious virus, labeling the requirements an important step along the way toward reopening the State House to the public.

The target date for a broader reopening still remains unclear. Last week, senators decided to keep their emergency rules, which allow for remote voting, in place until at least March 31.

Mariano and Senate President Karen Spilka have defended the Legislature's work in a mostly remote model during the pandemic, even as many other facets of public life such as schools and private offices have long since reconvened in-person with health and safety protocols.