Update Monday, Dec. 6 at 4:31 p.m.

Boston Mayor Michelle Wu announced Monday the city is now solidly in an "anticipated" winter COVID-19 surge, with the city's positivity rate at 5.2% — just above the 5% "threshold of concern" which indicates active spread of sickness.

The announcement came as Wu unveiled a new 18-member advisory committee to help guide the Boston's pandemic response.

"The first omicron case has just been detected in Massachusetts and we are seeing an anticipated holiday surge in COVID cases," said Wu, pointing to the state's first confirmed case of the newest emerging COVID-19 variant. "We will continue monitoring the situation extremely closely and follow the science at every turn."

Boston's strategy for combating the spread includes increasing access to vaccination and booster shots and making more tests available.

The city's latest surge overlaps with the broader, state-level uptick in COVID-19 cases and comes as medical experts work to identify the extent of waning immunity to the sickness.

Boston's positivity rate has not hit 5% since early April, according to the Boston Public Health Commission. But commission director Dr. Bisola Ojikutu, who also chairs the new COVID-19 advisory committee, said that while the new rate is cause for concern, the alarm is mitigated by Boston's large pool of vaccinated residents.

"We're at a different phase of the pandemic, realistically speaking," Ojikutu said, pointing to the 67% of Boston residents who are fully vaccinated. "But we know that we are in a winter surge right now and we will probably see an increase going forward. So we are being vigilant and taking the steps that I believe are necessary to address this issue."

Ojikutu acknowledged that Boston's hospitalization numbers are also climbing, but she said it's important to note "among hospitalized individuals, approximately two-thirds are unvaccinated."

"Measures taken by our local hospitals, including reducing the number of non-urgent procedures, will ensure that capacity and resources remain available if needed during the surge," Ojikutu said, adding later that she and the heads of Boston's local hospitals are in daily contact regarding capacity.

Wu said the new advisory group will be charged with considering a range of response actions, including proof of vaccination requirements for indoor recreation activities and potential vaccine mandates for the private sector workers, as New York City mayor Bill de Blasio announced Monday.

"Everything is on the table right now as we really seek to make sure that Boston is taking steps to head off the surge headed into this season and to make sure we're investing in our public health infrastructure in the right ways as the pandemic continues," Wu said.

Wu urged residents to get tested, vaccinated and "boosted," to stem the spread of infection.

This article was updated to include that Boston last had a positivity rate above 5% in April, per the Boston Public Health Commission.