Background Anti-tumour necrosis factor drugs such as infliximab are associated with attenuated antibody responses after COVID-19 vaccination. It is unknown how infliximab impacts vaccine-induced serological responses against highly transmissible Omicron variants, which possess the ability to evade host immunity and are now the dominating variants causing current waves of infection. Methods In this prospective, multicentre, observational cohort study, we investigated neutralising antibody responses against SARS-CoV-2 wild-type and Omicron BA.1 and BA.4/5 variants after three doses of COVID-19 vaccination in 1288 patients with IBD without prior COVID-19 infection, who were established on either infliximab (n=871) or vedolizumab (n=417). Cox proportional hazards models were constructed to investigate the risk of breakthrough infection in relation to neutralising antibody titres. Results Following three doses of COVID-19 vaccine, neutralising titre NT50 (half-inhibitory neutralising titre) was significantly diminished in patients treated with infliximab as compared to patients treated with vedolizumab, against wild-type, BA.1 and BA.4/5 variants (Fig 1). Patients with Crohn’s disease showed lower antibody NT50 compared to patients with ulcerative colitis against wild-type strain and BA.4/5 (Fig 2). Older age and thiopurine were independently associated with lower NT50 against wild-type strain and BA.4/5 (Fig 2). Non-white ethnicity was associated with higher NT50 compared to white ethnicity against wild-type strain, BA.1 and BA.4/5 (Fig 2). Breakthrough infection was significantly more frequent in patients treated with infliximab compared to patients treated with vedolizumab (Fig 3). Cox proportional hazards models of time to breakthrough infection after the third dose showed infliximab treatment to be associated with a higher hazard risk (HR) of 1.71 (95% CI [1.08 to 2.71], p=0.022) compared to vedolizumab (Fig 4). Higher neutralising antibody titres against BA.4/5 were associated with a lower hazard risk and a longer time to breakthrough infection (HR 0.87 [0.79 to 0.95] p=0.0028) (Fig 4). Conclusion Following a third COVID-19 vaccine dose, patients established on infliximab treatment have significantly lower neutralising titres against SARS-CoV-2, which were especially low against Omicron variants. Increased breakthrough infection in infliximab recipients was associated with lower neutralising antibody titres against BA.4/5. These data underline the importance of continued COVID-19 vaccination programs, including second-generation bivalent vaccines, especially in patient subgroups where vaccine immunogenicity and efficacy may be reduced.

Background Patients with Inflammatory bowel disease (IBD) receiving anti-TNF or JAK-inhibitor therapy have attenuated responses to COVID-19 vaccination. We aimed to determine how IBD treatments affect neutralising antibody responses against the currently dominant Omicron BA.4/5 variants. Methods We prospectively recruited 329 adults (68 healthy controls (HC) and 261 IBD) who had received three doses of COVID-19 vaccine at nine UK centres. The IBD population was established (>12 weeks therapy) on either thiopurine (n=60), infliximab (IFX) (n=43), thiopurine & IFX combination (n=46), ustekinumab (n=43), vedolizumab (n=46) or tofacitinib (n=23). Pseudoneutralisation assays were performed and the half maximal inhibitory concentration (NT50) of participant sera was calculated. The primary outcome was anti-SARS-CoV-2 neutralising response against wild-type (WT) virus and the BA.4/5 variant after the second and third doses of anti-SARS-CoV-2 vaccine, stratified by immunosuppressive therapy, adjusting for prior infection, ethnicity, vaccine type and age. Results Heterologous (two doses adenovirus vaccine, third dose mRNA vaccine) and homologous (three doses mRNA vaccine) vaccination strategies significantly increased neutralising titres against both WT SARS-CoV-2 virus and the BA.4/5 variants in HCs and IBD (fig 1). Antibody titres against BA.4/5 were significantly lower than antibodies against WT virus in both groups (Geometric Mean Ratio (GMR) [95% CI], 0.11 [0.09, 0.15], P<0.0001 in healthy participants; GMR 0.07 [0.06, 0.08], P<0.0001 in IBD patients). Multivariable models showed that neutralising antibodies against BA.4/5 after three doses of vaccine were significantly lower in IBD patients on IFX (GMR 0.44 [0.20, 0.97], P=0.042), IFX and thiopurine combination (GMR 0.34 [0.15, 0.77], P=0.0098) or tofacitinib (GMR 0.37 [0.15, 0.92], P=0.032), but not in patients on thiopurine monotherapy, ustekinumab or vedolizumab. Breakthrough infection was associated with lower neutralising antibodies against WT and BA.4/5 (P<0.05). Conclusion A third dose of COVID-19 vaccine based on the WT spike glycoprotein boosts neutralising antibody titres in patients with IBD. However, responses are lower against the currently dominant variant BA.4/5, particularly in patients taking anti-TNF or JAK-inhibitor therapy. Breakthrough infections are associated with lower neutralising antibodies and immunosuppressed IBD patients may receive additional benefit from bivalent vaccine boosters which target Omicron variants. Financial support was provided as an Investigator Sponsored Research Grant from Pfizer Limited.

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