OTTAWA, Dec 16 (Reuters) - The Omicron variant of COVID-19 is spreading rapidly in Ontario, Canada"s most populous province, and could overwhelm intensive care units early next month without prompt intervention, a panel of experts said on Thursday. "This will likely be the hardest wave of the pandemic," said Steini Brown, head of the Ontario COVID-19 Science Advisory Table. The panel released modeling which said increased vaccination alone would not be enough to fight Omicron. Instead, it called for public health measures to cut peoples" contacts by 50% and ensure the rapid roll-out of booster doses. "Omicron transmits very quickly ... without prompt intervention, intensive care unit occupancy could reach unsustainable levels in early January," said the modeling. Ontario, which accounts for just under 40% of Canada"s population, earlier reported 2,421 new daily cases, almost double the number from a week earlier. Nationwide the average number of new cases each day has risen about 75% in the past six weeks, according to a Reuters tally. "Our hospitals will still face incredibly strong pressures. This will come at an already challenging time when health care workers are fatigued or burned out from the preceding waves," Brown told a briefing. Ontario said on Wednesday it was limiting indoor events of over 1,000 people to 50% capacity. Brown said this was not enough to curb the rapid growth of Omicron. "There is still some uncertainty, but there"s also an undeniable urgency. Waiting to take action means waiting till it is too late," said Brown, urging people to wear high-quality masks and stick to well-ventilated indoor spaces. Canada"s government implored residents on Wednesday to avoid international trips. Prime Minister Justin Trudeau side-stepped questions about banning foreign travelers, saying Omicron was already spreading rapidly in Canada.