Effectiveness of first, second, and third COVID-19 vaccine doses in solid organ transplant recipients: A population-based cohort study from Canada

Abstract

Limited data exists on the effectiveness of a third COVID‐19 vaccine dose in solid organ transplant recipients. We conducted a population‐based cohort study using linked healthcare databases from Ontario, Canada to answer this question. We included solid organ transplant recipients ( n = 12,842) as of December 14, 2020, with follow‐up until November 28, 2021. We used an extended Cox proportional hazards model with vaccination status, including BNT162b2, mRNA‐1273, and ChAdOx1 vaccines, modeled as a time‐dependent exposure. Individuals started in the unvaccinated category (reference) and could contribute person‐time to first, second, and third doses. Over a median follow‐up of 349 days, 12.7% ( n = 1632) remained unvaccinated, 54.1% ( n = 6953) received 3 doses, and 488 (3.8%) tested positive for SARS‐CoV‐2 (of which 260 [53.3%] had a clinically important outcome [i.e., hospitalization or death]). Adjusted vaccine effectiveness against infection was 31% (95% CI: 2, 51%), 46% (95% CI: 21, 63%), and 72% (95% CI: 43, 86%) for one, two, and three doses. Vaccine effectiveness against clinically important outcomes was 38% (95% CI: 4, 61%), 54% (95% CI: 23, 73%), and 67% (95% CI: 11, 87%). Vaccine effectiveness in solid organ transplant recipients is lower than the general population, however, vaccine effectiveness improved following a third dose.

mRNA Vaccination Decreases COVID-19-Associated Morbidity and Mortality Among Organ Transplant Recipients: A Contemporary Cohort Study

“…To our knowledge, no other study to date has assessed the clinical efficacy of mRNA vaccination among OTRs during the Omicron surge using concurrent unvaccinated controls. Our findings and those of the above studies [ 3 , 10 ] support the recommendation to administer additional vaccine doses to moderately or severely immunosuppressed patients, which was originally based on immunogenicity data alone [ 12–14 ].…”

“…Our study has several limitations, which, nonetheless, are unlikely to have affected our core conclusions. First, it is a single-center report; therefore, the results may not be generalizable, although they are well aligned with those of many pre-Omicron studies [ 1 , 3 , 8 , 10 ]. Second, our cohort included mostly kidney transplant recipients; therefore, our conclusions may not necessarily apply to other OTRs.…”

“…Their findings were consistent with another report from a multistate registry, which also showed decreased efficacy among immunocompromised patients, especially OTRs, compared with immunocompetent hosts [ 1 ]. A recent population-based study among OTRs from Canada showed increasing protection with 3 > 2 > 1 COVID-19 vaccine doses, against both SARS-CoV-2 infection and severe COVID-19 [ 3 ].…”

Humoral response after a third and fourth dose of mRNA-based SARS-CoV-2 vaccine in previously seronegative kidney transplant recipients

“…. An important difference to outline between the two studies is the inclusion of vector-based vaccine type in the cohort study of Naylor et al [19].…”

COVID-19 in renal replacement therapy patients: an overview of current data and future challenges

“…A Canadian population study of a cohort of 12,842 organ transplant recipients shows that two-dose vaccination reduced the risk of hospitalization and death by 54% from COVID-19. The third dose of the vaccine raised this rate to 67% [86] (Supplementary material, Tables S1 and S2).…”