A study led by Dr. Hélène Decaluwe , professor in the Department of Pediatrics at the Université de Montréal and researcher at CHU Sainte-Justine, suggests that a combined approach of intramuscular and mucosal vaccines could be an effective avenue for preventing severe SARS-CoV-2 infections and reducing transmission of COVID-19. The study was conducted in close collaboration with Dr. Jennifer Gommerman’s team at the University of Toronto, and as part of CoVaRRNet, a Canadian research consortium focusing on respiratory virus variants of concern, including COVID-19.
Vaccination: intramuscular or intranasal?
One of the most important findings of the study is that the pathway by which the immune system is stimulated has a significant impact on the efficacy of the immune response. In fact, Dr. Decaluwe’s team found that a nasal infection with the Omicron variant in previously vaccinated individuals produced a more effective immune response than a booster vaccination by intramuscular injection.Given that mucosal vaccines tend to mimic a natural infection, without the associated infectious risk, the results of this new study show that a mucosal vaccine booster (intranasal, for example) could increase long-term protection against COVID-19 in vaccinated individuals.
Although intranasal vaccines against COVID-19 are not yet available in Canada and are the subject of further research, these results pave the way for new approaches to vaccination against COVID-19 for optimal immune response.
Effects of booster vaccines and natural immunity against COVID-19
The study, initiated in 2021, focuses on the period of emergence of the Omicron variant, when booster vaccines were introduced. The researchers looked at the benefits of booster vaccines and how they could help prevent hospitalizations and deaths related to COVID-19. Their aim was to understand how the immune system reacts to COVID-19, and what the differences in immune response are between people who have been vaccinated, those who have been naturally infected, and those who have had both the viral infection and the vaccine.To do this, the team set up two groups of subjects: 52 people who were infected early during the pandemic (from a larger group of 569 Montreal healthcare workers in the RECOVER study, led by Caroline Quach-Thanh from CHU Sainte-Justine), then vaccinated, and 71 others who were vaccinated without ever having been previously infected (as part of the CoVaRRNet cohort). The team identified those who had been infected with the Omicron variant and those who had received a booster vaccination. The researchers analyzed the immune response of each group, focusing on the antibodies produced and their ability to neutralize the virus, as well as the cellular immune memory response.
