Ab-C Study Tracks Omicron Spike, Quantifies Immune Response from Vaccination and Infection

The Action to Beat Coronavirus (Ab-C) continues to provide fresh insight into the course of the COVID-19 pandemic in Canada. The latest round of polling and dry blood spot collection took place a few months ago, from January to March 2022. The analysis, based on responses from about 5,000 ARF members, appears in a letter to The New England Journal of Medicine this week, showing that nearly 30% of Canadian adults — 9 million people—were infected with the Omicron variant of coronavirus in early 2022, compared to 10% in all previous waves combined.

One million of the infections were among the country’s 2.3 million unvaccinated adults – representing 40% of all unvaccinated adults. Even among vaccinated adults, 30% were newly infected by this highly transmissible variant. Combining information from polling and the laboratory, the Ab-C team were able to show that every dose of vaccine and previous infection boosted immune responses. Canadian adults with three vaccine doses and a history of COVID-19 had the most protection.

Despite widespread infection, it is unlikely that Omicron BA.1/1.1 will “immunize” everyone. In contrast to younger adults, those aged 60 or older face the highest rates of hospitalization and death and have the lowest rates of combined infection and vaccination. Strategies to build an “immunity wall” will continue to depend on increasing levels of vaccination, including boosters, among the unvaccinated, the partially vaccinated, and those who have recovered from infection. Ab-C will continue to track the COVID-19 pandemic and provide insights into the population’s immunity and vulnerability.