The Liberals first announced the plan in the midst of a resurgence of the virus just days before Trudeau triggered an early election last month.
He used the policy partly as justification for calling the vote with two years left in his mandate, saying that Canadians needed to decide how they wanted to see the pandemic brought to an end.
During the campaign, Trudeau routinely used vaccine mandates as a way to contrast the Liberals with the Conservatives, who opposed forcing people into getting a shot.
Once implemented, the vaccination rule would cover the federal civil service, travellers in federally regulated industries including airlines, trains and cruise ships, as well as workers in those fields.
When it was announced, the federal government said the requirement for public servants could apply as early as the end of September, and kick in for employees in federally regulated workplaces as well as commercial travellers "no later than the end of October."
Neither the Public Service Alliance of Canada (PSAC), one of the unions representing federal employees, nor the Treasury Board of Canada has specified when exactly the mandate will take effect.
Speaking Tuesday at his second news conference since being re-elected on Sept. 20, Trudeau said the public service has been working on the matter with unions.
"We will have more to say when we make the announcement in the coming weeks."
One of the big questions he's left lingering is what will happen to public servants who are not fully vaccinated, and don't have a valid medical reason as to why. During the campaign, Trudeau said unvaccinated federal workers would face "consequences," but didn't elaborate on what those would be.
Trudeau says moving on vaccine mandate for federal workers, travellers priority No. 1. #CDNPoli #COVID19 #Covid19vaccine
His warning prompted PSAC to say it opposed any employee losing their job because of their vaccination status.
Details have yet to be released around how the mandate will apply to domestic air and train travellers. The transport minister's office says the deadline of the end of October still stands, with the government set to discuss the policy with stakeholders, bargaining agents and those in the transportation sector.
National Airlines Council of Canada President Mike McNaney says the government has yet to provide it with the operational details of its plan, which it expects to come soon in order to meet the October deadline.
"We need to have both those nuts and bolts for us to implement. We need the public to be fully aware of what those … requirements are, so they too can be fully prepared."
In the absence of providing more specifics, Trudeau reiterated Tuesday that everyone 12 and older should make sure they are fully vaccinated against COVID-19 if they are planning a trip.
"You will not be able to travel on a plane or a train in Canada if you are not fully vaccinated," he said.
A WestJet spokeswoman said the company is still awaiting details on the announcement, and anticipates consultation with industry.
Morgan Bell added that includes "establishing a realistic date for implementation and discussions on how a shift to a fully vaccinated travel ecosystem will result in the recalibration of other COVID-19 travel-related measures implemented during the pandemic based on science and data."
Plane travellers must already adhere to other health rules, like wearing a mask, and throughout the pandemic have had to follow various quarantine and isolation requirements depending on their destination.
Most recently, Canada relaxed its border rules for travellers who are fully immunized against the virus with a Health Canada-approved vaccine.
McNaney says requiring domestic passengers to be fully vaccinated provides commercial aviation with another level of reassurance to consumers not necessarily seen in other industries, and believes that should be reflected when it comes to other COVID-19-related policies, such as travel bans.
Airline passenger rights advocate Gabor Lukacs also supports the federal policy, and believes if the government intends to move on it by the end of next month it needs to come up with a plan to deal with any administrative issues, as well as decide what's the most reasonable and effective means for travellers to provide proof of vaccination.
"The faster they want to introduce it, the more flexible the rule should be at least for a couple of weeks, a couple of months, to deal with screw-ups, to deal with errors, to deal with people who don't have the right paperwork and not create horrible consequences," he said.
"It has to be very, very flexible in terms of how you can prove that you've been vaccinated because we have so many different provinces."
The fact there is not yet a national vaccine passport system could lead to additional confusion, he said, but also pointed to how provincial driver's licences have long been a recognized way for domestic travellers to fly in Canada.
Finalizing a vaccine passport for Canadians travelling abroad, and helping to foot the bill for provinces that have moved forward with their own proof-of-vaccination system are also on the top of Trudeau's to-do list, he announced Tuesday.
Rounding out the prime minister’s list of five top priorities is protecting front-line health workers by ensuring that anyone who harasses or intimidates them faces criminal sanctions, Trudeau said.
He also said he will unveil a new cabinet next month that will be gender-balanced and recall Parliament this fall. Chrystia Freeland will remain as deputy prime minister and the country's finance minister.
This report by The Canadian Press was first published Sept. 28, 2021.