Dr Paul Molloy spoke out after it was confirmed Northern Ireland’s vaccine booster programme is to be accelerated with walk-in jabs now available for the over-30s.
The move follows Boris Johnson’s weekend warning that a “tidal wave of Omicron is coming”.
NI Health Minister Robin Swann said emergency measures were needed due to the potential threat posed by the new variant.
He said the speeding up of the vaccine programme was to administer as many booster doses as possible before the end of December.
As of Monday, ten cases of the Omicron variant had been detected in NI.
Dr Molloy said the Omicron projections were worrying.
“It seems to be more transmissible than previous variants and there is less protection from vaccines,” he said.
“What is still reasonable to expect is that, if you do get your vaccinations, you might still get the Omicron variant and you might pass it on but your risks of being hospitalised or dying are much less.”
He said that, with the Omicron variant now being seen in hospital wards and ICUs - which, he stressed, were already under “massive pressure” - the situation was “very, very concerning”.
He added: “In the next few days, GPs and our hospital colleagues will be working together to target all those due a booster and all those aged over 18, in particular... We have a responsibility to protect each other and the NHS.”
Meanwhile, Covid passports have become legally enforceable in NI.
The scheme requiring people to prove their Covid status to gain entry to a range of hospitality venues and larges attendance events kicked in on Monday.