Univariate associations and total effect estimates on antibody levels after third vaccine dose
| Characteristics | Beta (SE) (univariate) | P value (univariate) | Total effect (SE) | P value (total effect) |
| Age in years | −19.5 (9.2) | 0.035 | −19.5 (9.2) | 0.035 |
| Male gender | −316.3 (270.3) | 0.242 | −316.3 (270.3) | 0.242 |
| Pause in medication | 571 (359.4) | 0.112 | 383.4 (369.8) | 0.3 |
| Anti-Spike antibody level after second vaccine dose | 0.7 (0) | <0.001 | 0.6 (0) | <0.001 |
| Time between second and third dose | ||||
| Less than 3 months | (reference) | (reference) | ||
| Between 3 and 4 months | 1783.3 (421.2) | <0.001 | 1859.5 (421.2) | <0.001 |
| Between 4 and 5 months | 1753.1 (428) | <0.001 | 1963 (434.1) | <0.001 |
| More than 5 months | 2168.5 (423.7) | <0.001 | 2400.5 (430.4) | <0.001 |
| Diagnosis | ||||
| Rheumatoid arthritis | (reference) | (reference) | ||
| Spondyloarthritis | −787.7 (407.9) | 0.054 | −1150.4 (425.9) | 0.007 |
| Psoriatic arthritis | 405.4 (402.4) | 0.314 | 211.6 (408.1) | 0.604 |
| Crohn’s disease | −1084.9 (381.8) | 0.005 | −1858.4 (431) | <0.001 |
| Ulcerative colitis | −1054.7 (427.5) | 0.014 | −1732.8 (463.9) | <0.001 |
| Medication | ||||
| Tumour necrosis factor inhibitor, monotherapy* | (reference) | (reference) | ||
| Tumour necrosis factor inhibitor combination therapy† | −123.1 (339.8) | 0.717 | −463.9 (365.6) | 0.205 |
| Methotrexate | 2293.7 (356.1) | <0.001 | 2043.6 (443.5) | <0.001 |
| Vedolizumab | 1561.9 (670.3) | 0.02 | 2040.2 (694.5) | 0.003 |
| Janus kinases inhibitor | −1498.6 (784.2) | 0.056 | −1755.7 (813) | 0.031 |
| Ustekinumab, secukinumab, tocilizumab | 1919.8 (596) | 0.001 | 1962.6 (602.8) | 0.001 |
| Abatacept | −1054.8 (1137.3) | 0.354 | −1886.4 (1200.6) | 0.116 |
| Other‡ | 3335.2 (1322.8) | 0.012 | 3306.2 (1320.3) | 0.012 |
| Vaccine | ||||
| BNT162b2 | (reference) | (reference) | ||
| mRNA-1273 | 2221.6 (366.5) | <0.001 | 2212.3 (366) | <0.001 |
| Combination of vaccines§ | 1737.9 (302.9) | <0.001 | 1705.3 (303) | <0.001 |
Univariate associations with antibody level after third vaccination (BAU/mL), and estimated total effects from posited causal associations.
Total effect estimates based on posited causal model (online supplemental figure 4). Total effect of D estimated by model adjusting for M and G, denoted D|M, G; similarly: M|A, G, D; P|A, D, G, M; V|A, G; T|A, G; A|none; G|none; L|A, D, G, M. Here D=Diagnosis, M=Medication; p=Pause; V=Vaccine; T=Time between dose 2 and 3; A=Age; G=Gender; L=Antibody level after dose 2. All analyses were adjusted for time between vaccination and blood sampling.
*Tumour necrosis factor inhibitors: infliximab, etanercept, adalimumab, golimumab, certolizumab pegol.
†Combination therapy: tumour necrosis factor inhibitor in combination with either methotrexate, sulfasalazine, leflunomide or azathioprine.
‡Drugs with less than 10 patients included: sulfasalazine, leflunomide, azathioprine, risankizumab, prednisolone monotherapy.
§Combination of the following vaccines: ChAdOx1, BNT162b2, mRNA-1273.