Table 3. Association between post-vaccination infection and anti-Spike antibody levels within TwinsUK.

Logistic regression model results, testing association between post-vaccination infection, and Q2 anti-Spike antibody levels in single-vaccinated individuals within TwinsUK. Reference category was a Q2 antibody level in quintile 5 (highest 20%). Results present odds ratios, unadjusted 95% confidence intervals, and p-values adjusted for multiple testing.

Q2 antibody level	Post-vaccination infection incidence rate (%)	UnadjustedOR (95% CI), p-value	Adjusted for: Weeks since vaccinationOR (95% CI), p-value	Adjusted for: Age, sex, weeks since vaccinationOR (95% CI), p-value
Quintile 1 (lowest 20%): 0.4–18 BAU/mL	32/233 (13.7%)	3.23 (1.58–6.58), p=0.009	2.85 (1.39–5.86), p=0.03	2.93 (1.42–6.04), p=0.02
Quintile 2: 18–40 BAU/mL	20/226 (8.8%)	1.97 (0.92–4.21), p=0.11	2.04 (0.94–4.43), p=0.08	2.15 (0.99–4.68), p=0.06
Quintile 3: 40–73 BAU/mL	21/239 (8.8%)	1.95 (0.92–4.15), p=0.11	2.26 (1.04–4.92), p=0.06	2.41 (1.11–5.27), p=0.04
Quintile 4: 73–164 BAU/mL	21/230 (9.1%)	2.04 (0.96–4.33), p=0.11	2.39 (1.10–5.22), p=0.06	2.55 (1.17–5.58), p=0.04
Quintile 5 (highest 20%): ≥164 BAU/mL (reference)	11/234 (4.7%)	1.00	1.00	1.00