Three COVID-19 vaccine doses significantly reduced infection, severe outcomes in organ transplant recipients

September 14, 2022

Dr. Greg Knoll“Our findings suggest there is urgent need to encourage vaccine uptake among this immunocompromised population,” - Dr. Greg KnollDr. Greg Knoll led one of the few real-world studies of the effectiveness of a third dose of COVID-19 vaccine among organ transplant recipients by using linked healthcare databases. 

Transplant recipients have a reduced antibody response to vaccines because they need to take drugs that suppress their immune system. Due to this reduced immune response, we didn’t know how well COVID-19 vaccines protected transplant patients from the virus. 

Following anonymized data from 12,842 Ontario transplant recipients from Dec 14, 2020 to Nov 28, 2021, the study team found that the effectiveness of one, two and three doses of vaccine for preventing COVID-19 infection in this population was 31%, 46% and 72% respectively. The effectiveness of these doses for preventing hospitalization or death was 38%, 54% and 67% respectively. 

This shows that the vaccine’s effectiveness for preventing infection and severe outcomes was lower in organ transplant recipients than in the general population, which was estimated to be around 90% during this pre-Omicron period. However, it also shows that vaccine effectiveness in this population improved significantly after the third dose.

“Our findings suggest there is urgent need to encourage vaccine uptake among this immunocompromised population,” says Dr. Greg Knoll, OHRI Senior Scientist, Chair/Head, Department of Medicine at The Ottawa Hospital and uOttawa.

Authors: Kyla L. Naylor, Sang Joseph Kim, Graham Smith, Eric McArthur, Jeffrey C. Kwong, Stephanie N. Dixon, Darin Treleaven, Gregory A. Knoll

Source: American Journal of Transplantation

Core Resources: ICES

Funders: This study was supported by ICES, which is funded by an annual grant from the Ontario Ministry of Health (MOH) and the Ministry of Long-Term Care (MLTC)

The Ottawa Hospital is a leading academic health, research and learning hospital proudly affiliated with the University of Ottawa and supported by The Ottawa Hospital Foundation.