A recent study shows small differences in COVID-19 vaccine effectiveness among dialysis patients in British Columbia compared to Ontario, which may be caused by variability in pandemic waves or vaccine rollout strategies across the two provinces. However, the results of the study suggest dialysis patients in both regions were substantially protected from COVID-19-related hospitalization or death because of the vaccines.
When the World Health Organization first released information about COVID-19 vaccines, it noted vaccine effectiveness might vary across regions and populations. As the vaccines were rolled out in Canada, both BC and Ontario collected detailed information about infection and vaccination rates in dialysis patients – providing a prime opportunity to explore how vaccine effectiveness may vary across provinces.
Mohammad Atiquzzaman is a researcher with BC Renal who helped lead the comparison study. His team analyzed vaccine and infection rate data from more than 4,000 dialysis patients in BC and more than 13,500 dialysis patients in Ontario.
The results show that the vaccinated BC group had an overall lower risk of COVID-19 infection compared to the vaccinated Ontario group, while the Ontario group appeared to have better protection against COVID-19-related hospitalization or death with two doses of vaccines compared to the BC group. It’s important to note that these effects were not statistically significantly different from each other.
Ontario experienced two pandemic waves over the study period, whereas BC only experienced one. Therefore, the Ontario population was generally more exposed to the virus. Despite the differences in exposure, other factors may also explain the variability observed between the provinces, such as differences in vaccine rollout strategies, Atiquzzaman says. Notably, Ontario had a median of 39 days between when a person received their first and second dose, and BC had a much longer period of 77 days. Later on, evidence began to emerge suggesting that longer times between first and second doses of mRNA vaccines could result in better vaccine effectiveness – which may explain the noticeable but not statistically significant differences in vaccine effectiveness between Ontario and BC.
“There’s a bit of a difference between the provinces, but at the end of the day, the vaccine was highly effective in both regions,” explains Atiquzzaman. “Most people were protected by the vaccines.”Publication: COVID-19 Vaccine Effectiveness Among Patients With Maintenance Dialysis; Observations From Population Level Cohort Studies in 2 Large Canadian Provinces