Uptake of third doses of SARS-CoV-2 vaccines among people with inflammatory bowel disease in Ontario, Canada.

Patients with inflammatory bowel disease (IBD) are often treated with immunosuppressive medications, which are associated with decreased antibody response to initial SARS-CoV-2 vaccination and waning antibody levels following a second dose.1, 2 The province of Ontario, Canada began offering third doses of SARS-CoV-2 vaccines to priority groups, including individuals with IBD on immunosuppressive therapy, beginning Sept 14, 2021, followed by everyone aged 18 years and older on Dec 20, 2021. We describe and compare vaccine uptake in people with and without IBD as of Jan 9, 2022.

We used health administrative data from Ontario, Canada for this population-based retrospective cohort study. Data include demographic characteristics, health-care encounters, and SARS-CoV-2 vaccinations for all provincial residents eligible for universal health-care coverage (>99% of the population). We identified all patients with IBD aged 18 years or older living in Ontario as of Sept 1, 2021 using validated algorithms5, 6 and compared them with people without IBD. Vaccination status was obtained from COVaxON, a comprehensive registry containing information on vaccine product, date of administration, and dose number for all vaccines administered in the province. COVaxON also includes out-of-province vaccinations reported to local public health units.

We determined overall and age-specific weekly cumulative incidence of first, second, and third doses of vaccination against SARS-CoV-2. We calculated the relative risk (RR) and corresponding 95% CI of vaccination. Third doses were assessed in the full population and among those with two doses. Analyses were done with SAS version 9.4 and R software.

Among 107 059 patients with IBD, 89·9% had one dose of a SARS-CoV-2 vaccine, 88·6% had two doses, and 58·3% had three doses as of Jan 9, 2022. Among 12 145 893 individuals without IBD, 85·6% had one dose, 83·8% had two doses, and 44·3% had three doses (RR for third doses 1·32, 95% CI 1·31–1·32; appendix). Among individuals with IBD, those between 18 and 39 years of age were least likely to receive a third dose (41·4%) but this age group had the highest uptake of third doses relative to the general population (RR 1·47, 95% CI 1·45–1·49).

In conclusion, in Ontario, Canada, where universal vaccination is available, there is higher uptake of third doses of SARS-CoV-2 vaccines among patients with IBD relative to the general population, but coverage remains suboptimal. Although the number of people with third doses is climbing, we expect these rates to plateau in both populations. As with first and second doses, we expect patients with IBD to have higher uptake of third doses than those without IBD. Efforts should be made to understand reasons for third dose vaccine hesitancy in patients with IBD, particularly in the Omicron era.

SB reports grants from the Public Health Agency of Canada. GGK has received honoraria for speaking or consultancy from AbbVie, Janssen, Pfizer, and Takeda; research support from Janssen, AbbVie, GlaxoSmithKline, Merck, and Shire; and shares ownership of a patent for treatment of inflammatory disorders, autoimmune disease, and PBC (UTI Limited Partnership, assignee. Patent 62/ 555,397). EIB has acted as a legal consultant for Hoffman La-Roche Limited and Peabody & Arnold LLP and consultant for McKesson Canada for matters unrelated to a medication used to treat inflammatory bowel disease or COVID-19. All other authors declare no competing interests. This project was supported by funding from the Public Health Agency of Canada, through the Vaccine Surveillance Reference group and the COVID-19 Immunity Task Force. The views expressed herein do not necessarily represent the views of the Public Health Agency of Canada. The study is supported by ICES, which is funded by the Ontario Ministry of Health (MOH) and the Ministry of Long-Term Care. Parts of this material are based on data and information compiled and provided by MOH and the Canadian Institute for Health Information. The opinions, results, and conclusions reported in this paper are those of the authors and are independent of the data sources; no endorsement is intended or should be inferred. JW receives support from the Arthritis Society Stars Career Development Award (STAR-19-0610).