Table 4. Possible predictors for decreased antibodies after 10 to 12 months compared with increased, unchanged and antibody ≥ 10 using univariate analysis adjusted for age and sex, and multivariate analysis adjusted for all variables.

		Univariate analysis				Multivariate analysis
		OR	2.5%	97.5%	p-value	OR	2.5%	97.5%	p-value
Age (numeric)		0.97	0.94	0.99	0.01	0.97	0.93	1.00	0.030
Gender	Female	ref				ref
	Male	0.92	0.46	1.85	0.81	0.77	0.32	1.85	0.563
BMI kg/m 2	< 25	ref				ref
	≥ 25	2.34	1.06	5.42	0.04	2.15	0.9	5.41	0.093
Education	Below University	ref				ref
	University < 4 years	0.79	0.35	1.76	0.57	0.60	0.23	1.50	0.278
	University ≥ 4 years	0.83	0.30	2.15	0.71	0.50	0.14	1.62	0.265
Income Norwegian kroner	< 500 000	ref				ref
	500 000–1000 000	0.47	0.16	1.41	0.17	0.61	0.19	2.12	0.425
	> 1000 000	0.62	0.23	1.77	0.35	0.82	0.25	2.87	0.743
Smoking	Non-smoker	ref				ref
	Past smoker	0.37	0.12	0.96	0.06	0.34	0.11	0.93	0.049
	Daily and occasional smoker	0.37	0.06	1.46	0.21	0.37	0.05	1.62	0.240
Symptoms
Symptoms scorea (numeric)		1.0	0.85	1.08	0.48	0.97	0.84	1.11	0.612
Dyspnoea	No	ref
	Yes	1.02	0.50	2.08	0.97	not included
Fever with chills/sweating	No	ref
	Yes	0.33	0.13	0.75	0.01	not included
Abdominal pain/diarrhoea/ nausea	No	ref
	Yes	1.69	0.78	3.59	0.18	not included
Loss of smell and taste	No	ref
	Yes	1.17	0.53	2.74	0.71	not included
Comorbidity score a		1.02	0.61	1.62	0.93	1.08	0.61	1.84	0.774

^a Total symptom and comorbidity scores were calculated by adding the number of symptoms or comorbidities for each participant, and used instead of single variables in the multivariate analysis.