Background/Purpose: COVID-19 vaccines are now being offered as regular boosters every 6-12 months for people with autoimmune rheumatic diseases, particularly for people on rituximab, where serological responses to vaccination are poor. We were interested in understanding the preferences of patients taking rituximab for a booster with the same messenger RNA (mRNA) vaccine, versus a switch to a protein subunit vaccine.

Methods: We conducted a discrete-choice experiment (DCE) within a clinical trial comparing vaccine types for 4^th (Trajectory A) and 5^th (Trajectory B) doses in people with autoimmune rheumatic diseases, all of whom had received prior mRNA vaccines. In this open label, non-randomized, comparative trial, people could choose between an mRNA or protein subunit vaccine. In the DCE, people were asked to choose between two different vaccine types or “no vaccine” in a series of ten hypothetical questions, where the vaccine choices varied in terms of their effectiveness, likelihood of a flare, and type of vaccine (same (mRNA) versus switch to a protein subunit vaccine). The DCE was administered by computer in French and English at the two trial sites in Quebec, Canada. We used a hierarchal Bayes model with continuous levels to estimate average and individual part-worth utilities and attribute importance across the range of levels presented for the three attributes. We compared the preferences of people who chose the different vaccine types through a Wilcoxon rank-sum test on the median individual part-utility values.

Results: Among 78 people who agreed to participate, 69 (88%) completed the survey.Participants had an average age of 58 years, 78% were female, and 58% had above high school education. The type of autoimmune disease was rheumatoid arthritis (43%), ANCA associated vasculitis (32%), systemic lupus erythematosus (9%) and other (16%), with a median disease duration of 9 years. 65% of respondents had a prior COVID-19 infection at study entry. Of the 69 participants, 36 (52%) people chose an mRNA vaccine and 33 (48%) people chose a protein subunit vaccine. On average, people preferred to stay with the same vaccine type, rather than switch to a protein subunit vaccine. However, people would accept a protein subunit vaccine if it was associated with an 18% absolute increase in effectiveness, or a 6% absolute reduction in the risk of flare. People who chose the protein subunit vaccine placed a higher importance on vaccine effectiveness (p < 0.001) and lower importance on vaccine type (p < 0.001).

Conclusion: People with autoimmune diseases on rituximab who had received prior mRNA COVID-19 vaccines preferred to stay with mRNA vaccines for subsequent doses unless the new protein subunit vaccine was substantially more effective (~20%) or safe, although variability in preferences was found. This supports current approaches of booster immunizations with the same vaccine, and provides an estimate of what would be considered a worthwhile increase in effectiveness for high-risk patients to choose a different vaccine type.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/switch-or-stay-the-same-preferences-of-people-with-autoimmune-disease-on-rituximab-for-different-types-of-covid-19-vaccine-boosters/