Table 3.

Risk factors for modified vaccine effectiveness.

Risk factor		Number of vaccinated cases	Person-years of vaccinated subjects	Number of unvaccinated cases	Person-years of unvaccinated subjects	Vaccine effectiveness (95% CI)	Relative difference, % (95% CI)
Age
	Routine cohort (70 yrs)	130	42,121	952	101,001	0·68 [0·62; 0·74]	Refa
	Catch-up cohort (78–79 yrs)	123	35,369	773	77,228	0·65 [0·59; 0·72]	−3·6 [−16·4; 9·1]
Gender
	Male	100	36,733	698	83,494	0·68 [0·61; 0·75]	Ref
	Female	153	40,757	1027	94,734	0·66 [0·60; 0·72]	−3·3 [−16·0; 9·5]
Ethnicity
	Caucasian	234	70,452	1590	155,707	0·67 [0·63; 0·72]	Ref
	Non-Caucasian	10	2474	39	6993	0·27 [−0·23; 0·78]	−59.3 [−134·0; 15·5]
Index of Multiple Deprivation
	< 5th quintile	229	69,798	1553	157,422	0·67 [0·63; 0·72]	Ref
	5th quintile	24	7674	171	20,744	0·63 [0·47; 0·79]	−6·0 [−30·3; 18·2]
Asthma
	No	209	65,970	1427	153,096	0·67 [0·62; 0·71]	Ref
	Yes	44	11,520	298	25,132	0·68 [0·58; 0·78]	1.8 [−15·2; 18·8]
Type 2 diabetes
	No	183	61,470	1395	143,769	0·70 [0·65; 0·75]	Ref
	Yes	70	16,020	330	34,460	0·55 [0·43; 0·66]	−22·0 [−39·6; −4·5]
Chronic obstructive pulmonary disease (COPD)
	No	232	71,632	1569	163,994	0·67 [0·62; 0·71]	Ref
	Yes	21	5858	156	14,234	0·67 [0·52; 0·82]	0.8 [−22·6; 24·2]
Smoking
	Non-smoker	133	36,757	800	77,434	0·65 [0·59; 0·71]	Ref
	Ex-smoker	83	26,604	567	57,061	0·68 [0·61; 0·76]	5·0 [−10·2; 20·3]
	Smoker	20	5984	167	20,368	0·60 [0·41; 0·78]	−8.4 [−38·5; 21·8]
Body mass index (BMI)
	Normal weight (18·5– 24.9)	56	17,309	362	37,062	0·67 [0·58; 0·76]	Ref
	Underweight (<18·5)	4	1973	59	5476	0·82 [0·63; 1·00]	21·7 [−10·9; 54·4]
	Overweight (25–29.9) or obese (>30)	159	45,083	962	95,361	0·65 [0·59; 0·71]	−2·8 [−18·8; 13·3]
Immunocompromised
	No	241	75,992	1649	173,438	0·67 [0·63; 0·72]	Ref
	Yes	12	1498	76	4791	0·49 [0·19; 0·80]	−26·8 [−72·8; 19·3]
Immunosuppressed
	No	245	75,948	1659	173,949	0·67 [0·62; 0·71]	Ref
	Yes	8	1542	66	4280	0·66 [0·41; 0·91]	−1·1 [−38·9; 36·7]
History of herpes zoster
	No	208	68,635	1512	158,845	0·69 [0·64; 0·73]	Ref
	Yes	45	8855	213	19,384	0·53 [0·38; 0·68]	−22·5 [−44·9; −0·1]
Co-administration with influenza vaccine
	No	164	48,708	1725	178,229	0·66 [0·60; 0·71]	Ref
	Yes	89	28,782	–	–	0·68 [0·62; 0·75]	4·0 [−8·9; 17·0]
Co-administration with pneumococcal vaccine
	No	251	76,567	1725	178,229	0·67 [0·62; 0·71]	Ref
	Yes	2	923	–	–	0·77 [0·45; 1·00]	15·2 [−33·5; 63·9]

^aRef = reference group.