On September 12 of this year, Health Canada approved the new Moderna Covid-19 vaccine targeting the XBB.1.5 variant for all Canadians over the age of six months.

This announcement comes a day after the US Food and Drug Administration (FDA) approved the new version of the Pfizer and Moderna vaccines.

However, the FDA has not approved the vaccine developed by Novavax. The company's stock fell on Monday after this announcement.

So far, Canada has only granted approval for the vaccine produced by the American company Moderna.

Canadian health authorities stated that the approval applications for the new Novavax and Pfizer vaccines are still under review.

It is also recommended that children aged 6 months to 4 years who have not been vaccinated receive two doses, while children who have already been vaccinated only receive one dose. Two doses are recommended for younger children because it is very likely that these populations have inadequate immunity against Covid-19.

Individuals over the age of 5 will be able to receive one dose, as long as they received their last booster more than six months ago.

This new vaccine aims to combat the XBB.1.5 variant, which is part of the Omicron variant family of Covid-19.

Although this monovalent vaccine is not designed against currently dominant variants, data confirms that it provides good protection against various circulating variants, including EG.5 and BA.2.86.

The first vaccines were monovalent, targeting the original strain of the SARS-CoV-2 virus that emerged in 2019. The booster doses that began to be administered in the second half of 2022 were bivalent, designed against the original strain of SARS-CoV-2 and against the Omicron variant. Moderna focused on BA.1 while Pfizer focused on the BA.4/BA.5 variants.

The vaccine that will be available in the coming months is a monovalent vaccine targeting the XBB.1.5 Omicron variant.

The recent resurgence of Covid-19 cases detected in Canada is currently driven by the EG.5 variant, known as Eris, which is a strain similar to XBB.1.5.

Although XBB.1.5 is in decline, many of its sublineages are still circulating. In the United States, XBB.1.5 is present. The Centers for Disease Control and Prevention (CDC) stated that nearly a quarter of infections are currently caused by EG.5 variants.

In Quebec, XBB.1.5 dominated throughout the summer, but by the end of August, it accounted for less than 10% of cases attributed to this variant.

In Ontario, as of mid-August, 21% of cases were attributed to the EG.5.1 variant; 8.2% to the FL.1.5.1 variant, and 7.3% to the XBB.1.16 variant.

Meanwhile, the World Health Organization is also closely monitoring the BA.2.86 variant because it has 30 additional mutations in the spike protein, which helps the virus enter human cells, compared to the BA.2 subvariant of Omicron.

BA.2.86 has been detected in Canada, with 11 cases reported so far.

In the United States, the CDC is expected to soon announce its recommendations for the upcoming vaccination campaign.

In Canada, it will be up to the provinces to determine who will be prioritized for this booster dose or whether the entire population will receive the vaccine. The National Advisory Committee on Immunization (NACI) already recommends that individuals who were vaccinated or infected more than six months ago receive a dose of the new vaccine formulation if at least six months have passed since their last Covid-19 vaccine dose.

Less than 6% of eligible residents have received a vaccine dose in the past six months.

While a high percentage of Canadians have gained hybrid immunity during the recent waves, NACI states that protection against infection decreases over time.