Correlates of breakthrough Omicron (B.1.1.529) infections in a prospective cohort of vaccinated patients with rheumatic diseases

BACKGROUND: Data on the effectiveness of SARS-CoV-2 vaccines and the durability of protection against the prevalent Omicron variant are scarce, especially in patients with autoimmune rheumatic diseases (AIRDs). Hence, we prospectively studied Omicron breakthrough infections in patients with AIRDs and attempted to isolate associated risk factors. METHODS: Patients with AIRDs who had completed primary vaccination with either AZD1222 or BBV152 vaccines were included and prospectively followed up from January 2022 onwards for the development of breakthrough Omicron infections. The time interval from the last event [2nd dose of vaccination (V) or past COVID-19 infection (I) whichever was later] to Omicron infection was recorded. Patients were divided based on the events and their order of occurrence into V + V, V + I, I + V, V + I + V, and V + V + I groups. The incidence of breakthrough infections and their predictors were studied with a focus on the vaccine type and hybrid (H) immunity (vaccinated individuals with a history of COVID-19 infection). RESULTS: We included 907 patients with AIRDs (53.5 ± 11.7 years and a male-to-female ratio of 1:5.1), and the majority of patients had received AZD1222 (755, 83.2%). Breakthrough infections were observed in 158 of 907(17.4%) of which 97 (10.4%) were confirmed by RT-PCR. Breakthrough infections were significantly greater in the V versus the H group (15.7% and 3.5%, log-rank test, p = < 0.01). Among the hybrid group, the order of infection and vaccination had no bearing on the risk of breakthrough infections. On multivariate analysis, breakthrough infections were significantly lesser in the H versus the V group [HR: 0.2(0.1–0.4); p = 0.01]. CONCLUSION: The risk of breakthrough Omicron infections in fully vaccinated patients with AIRDs was 17.4% with a significantly lower risk in patients with hybrid immunity.