TORONTO -- As the election campaign heads into a week with two official debates, vaccines have re-emerged as a wedge issue for the federal party leaders.

During a campaign event in Welland, Ont. on Monday, Liberal Leader Justin Trudeau said provincial COVID-19 vaccine passports 鈥� already in use in Quebec and Manitoba, witha planned passport expected for Ontario later this month 鈥� are only an 鈥渋nterim measure鈥� until a national version is available next year.

鈥淲e have decided that the best way to do that is to work with each of them so that they are reasonably standardized across the country and so that there is a federal certification on that will be accepted for international travel,鈥� Trudeau said during the event.

Trudeau also announced that, if re-elected, the government would table legislation to protect businesses from legal recourse if they ask for proof of a COVID-19 vaccination.

Over the weekend, Conservative Leader Erin O鈥橳oole set a goal of fully vaccinating 90 per cent of eligible Canadians, through paid time off for employees and providing transportation to get a shot.

According to CTVNews.ca鈥檚 vaccine tracker,  76.7 per cent of eligible Canadians are fully vaccinated, while 83.8 per cent have received at least one dose.

Public health officials believe more than 80 per cent of Canadians need to be fully vaccinated to avoid overwhelming the health-care systemwith COVID-19 cases.

O鈥橳oole has proposed an 鈥渁lternative鈥� approach to mandatory vaccines that includes a reliance on rapid testing for those who are not vaccinated.

鈥淚t's about having an approach of respect and trying to work with people to overcome any concerns about vaccinations or also make sure that they work to use daily rapid testing, masking, distancing to - to fight COVID-19,鈥� he said.

On Monday, O鈥橳oole would not disclose how many of his candidates have been vaccinated, citing the importance of choice and privacy.

Trudeau has said every Liberal candidate -- except for one with a medical exemption 鈥� has been fully vaccinated and called O鈥橳oole鈥檚 refusal to disclose his party鈥檚 vaccination status as pandering to the 鈥渇ringe鈥� anti-vaccine Canadians.

On Sunday, NDP Leader Jagmeet Singh announced a billion-dollar plan to increase vaccination across the country that includes targeting the remote areas of Canada and vaccine hesitant groups, as well as implementing a national vaccine certificate for both domestic and international travel.

Singh had previously called for the federal government to enforce mandatory vaccinations for federal workers and implement a national vaccine passport for international travel by Labour Day.

Bloc Quebecois Leader Yves-Francois Blanchet has said previously that he supports a vaccine passport for international travel.

The Green Party has yet to unveil its platform, but Leader Annamie Paul said the party is 鈥渃onsidering very seriously鈥� vaccine mandates for the federal public service.

People鈥檚 Party of Canada Leader Maxime Bernier, who has said he won鈥檛 receive a vaccine, is opposed to all vaccine passports.

With files from CTV National News Senior Political Correspondent Glen McGregor and The Canadian Press