Authorities were on alert after Tuesday's cases, having confirmed the 17-year old was a household contact of a woman who recently travelled from NSW.
Chief Health Officer Jeannette Young described Wednesday's result was "excellent news" and said she was "fairly comfortable" given the level of testing and limited exposure recent cases had in the community.
She said the 17-year-old was likely infected after a family member visited from northern NSW and stayed with him for three days last week.
"That person, when they went back to New South Wales, tested positive," Dr Young said.
She said the NSW resident was not in the community aside from catching the bus, and route 700 between Coolangatta and Miami has been added as an exposure site on October 19 and 20.
It is unclear whether any border restrictions were breached, and Dr Young said there were valid reasons to cross from the northern NSW bubble such as essential work, study and health care.
The second case recorded on Tuesday, a woman in her 30s who was in home quarantine after travelling from Melbourne, was deemed lower risk.
Meanwhile, Dr Young is pleading with unvaccinated Queenslanders to get the jab as soon as possible so they are protected when borders reopen on December 17.
"This is our window to get fully vaccinated so please, anyone that hasn't had their first dose, you need to have it this week," she said.
More than 75 per cent of eligible Queenslanders have had their first jab, and more than 61 per cent are fully vaccinated.
It comes as the deadline looms for the state's healthcare workers to be vaccinated or successfully apply for an exemption.
Health Minister Yvette D'Ath said more than 90 per cent of the workforce was vaccinated, with "around 2000" indicating they hadn't had the jab.
"These people will be given a show cause come the first of November if they haven't had at least one dose," she said.
"We make no apologies whatsoever for mandating vaccinations of our health workers and aged care, they are dealing with the most vulnerable people in our community."
The state recorded one new case in hotel quarantine.
AAP with The Project