University of Waterloo Study Confirms Vaccine Efficacy Against COVID Strains

A new study from the University of Waterloo has examined the effectiveness of current COVID-19 vaccines against evolving strains of the virus. Conducted by researchers including Yangjianchen Xu, an assistant professor in the department of statistics and actuarial science, the observational research analyzed data from approximately 1.8 million residents in Nebraska over a seven-month period between 2024 and 2025.

The data for this comprehensive study was sourced from various systems, including the Nebraska electronic disease surveillance system and the state immunization information system. Collaborating institutions included the UNC Gillings School of Global Public Health and the University of Nebraska Medical Center.

Yangjianchen Xu explained in a recent interview on CBC K-W’s The Morning Edition that the goal of the study was to evaluate the real-world effectiveness of vaccines that had been authorized by the U.S. Food and Drug Administration (FDA). “These vaccines were authorized… without providing evidence that these vaccines are effective,” Xu stated. “Our study aims to fill this gap.”

Through their research, the team found that the latest vaccines demonstrated significant effectiveness against severe COVID-19 outcomes, including hospitalization and death. The findings revealed that the vaccines were most effective four weeks post-vaccination, showing a 44.7 percent effectiveness against infection, 45.1 percent against emergency department visits, and 57.5 percent against hospitalization or death. However, effectiveness declined over time, dropping to 35 percent against infection at ten weeks and down to 16.7 percent by twenty weeks.

“This is the largest study I know of regarding this vaccine,” Xu noted. “Having a large sample allows us to accurately estimate vaccine effectiveness.” He anticipates that as the virus continues to evolve, new vaccine variants will be developed, and he plans to continue research to assess their effectiveness.

The lead author of the study, Danyu Lin, a distinguished professor at the Gillings School, commented on the results, stating, “Our study showed that vaccines in 2024 to 2025 were effective, especially against severe outcomes, although their effectiveness waned over time.” He also noted that the effectiveness against different Omicron subvariants remained consistent.

In light of the study’s findings, Dr. Nicola Mercer, medical officer of health for Wellington-Dufferin-Guelph Public Health, emphasized the importance of keeping vaccinations up to date as winter approaches. “It impacts people who don’t even get sick,” she cautioned, highlighting the burden on healthcare systems when respiratory viruses surge.

Dr. Mercer urged those hesitant about vaccinations to consult their healthcare providers to understand the importance of vaccines in protecting vulnerable populations. “If you have a newborn in your family or elderly relatives, getting vaccinated can help protect them,” she added.

Furthermore, David Aoki, director of infectious disease and chief nursing officer at Region of Waterloo Public Health, reiterated the significance of vaccination in preventing illness. “We continue to offer COVID vaccines free of charge… Study after study has shown their effectiveness and safety,” he affirmed. Aoki warned that colder weather often leads to increased virus transmission, making vaccination crucial during these months.

This study not only sheds light on the effectiveness of current vaccines but also underscores the ongoing need for public health efforts in vaccination campaigns as new strains of COVID-19 emerge.