With early signs indicating the COVID-19 caseload is poised to grow in the weeks ahead, Health Canada is actively reviewing three new vaccines specifically designed to target an Omicron subvariant of the virus.

The department told CBC News Monday that new mRNA vaccines from Pfizer and Moderna and a non-mRNA product from Novavax have been part of a months-long review process and supplies could start to roll out in the fall.

That timeline is similar to what is planned south of the border. The U.S. is poised to release an updated COVID booster in late September (new window) once regulators there sign off on the new shots.

These new vaccines are designed for the XBB.1.5 Omicron subvariant now in widespread circulation.

When asked how many doses of these products the country is set to receive, a Health Canada spokesperson wouldn’t give an exact figure but said in a media statement there will be an ample supply of the new formulation of mRNA vaccines.

Pfizer CEO Albert Bourla has said the company’s shots are ready to be deployed as soon as regulators authorize their use.

Novavax’s protein-based XBB COVID vaccine candidate will not be available until later this year, Health Canada said.

That shot is an option for people who are unwilling or unable to receive an mRNA vaccine, the department said.

While the number of reported COVID-19 cases remains much lower than in the past, some agencies, notably Public Health Ontario (PHO), have reported an uptick in positive test results.

Of the roughly 12,700 tests administered in the province between Aug. 13 and Aug. 19, 9.9 per cent came back positive (new window) — a sharp increase from the 5.2 per cent positivity rate in early July.

Per cent positivity remained stable from late April 2023 to the end of May, trended downwards until late June and has been trending upwards overall with the trend accelerating in the most recent weeks, PHO said in an update on respiratory viruses published Friday (new window).

Despite an expected fall wave of COVID-19, health experts recommend most people wait for the next, updated vaccine — still a few weeks away — to get a booster for the most protection.

Ontario wastewater signals (new window) also suggest that COVID-19 infections are steadily increasing in number — although not to the high levels reported earlier this year.

The number of COVID-related hospitalizations in Ontario has been stable for months, despite an increase in test positivity.

The most commonly reported COVID-19 strain in Ontario is currently EG.5.1, followed by EG.5.1.1 and XBB.1.16, PHO said.

The new formulation of the vaccines could help with these subvariants, which are strains of the virus descended from the original Omicron.

Some Canadians remain opposed to taking COVID-19 vaccines. Health Canada sought to reassure those people that the products are going through an independent process that is based on scientific rigour and medical evidence.

The federal government is working with the provinces and territories on demand planning and forecasting to determine how many shots will be made available for the fall 2023 vaccination campaign, the spokesperson said.

While it’s up to Ottawa to buy the shots, lower levels of government are ultimately responsible for designing and delivering immunization programs.

With the review of those products now well underway, the National Advisory Committee on Immunization (NACI) is recommending (new window) that all people previously vaccinated against COVID-19 prepare to get a dose of the new formulation once it’s available.

NACI, an independent body made up of volunteer vaccine experts, said an eligible individual should receive a shot if at least six months have passed since a previous COVID-19 vaccine dose or infection.

The committee said immunization is particularly important for people facing a heightened risk of infection, such as those 65 years of age or older, long-term care home residents, pregnant women, First Nations, Metis and Inuit people and other racialized groups.

The new formulations under review are targeted to address the more recent, immune-evasive variants in circulation, NACI said (new window).

People with an updated shot will benefit from a better immune response against these variants compared to the current crop of vaccines, the committee said.

A booster dose starting in the fall of 2023 is expected to increase protection against SARS-CoV-2 infection and COVID-19 symptomatic and severe disease that has waned since the last booster vaccination or SARS-CoV-2 infection, NACI said in making its recommendation.

Increased protection will help to reduce the impact of COVID-19 on the health system while other respiratory viruses, including influenza and RSV, are circulating in the fall and winter of the 2023-2024 respiratory virus season.

The committee said hybrid immunity — prior infection along with vaccination — offers greater protection against infection and severe disease than vaccination or prior infection alone.

For this reason, an additional dose of vaccine starting this fall is particularly important for those who have not been previously infected and have protection from vaccination alone, the committee said.

Relatively few COVID-19 shots have been administered in Canada this year.

Federal data on immunization is also out of date as uptake for these products has waned considerably.

As of June 18, 2023, about 6 per cent of the population has had a COVID-19 shot in the last six months.