Table 2.

Characteristics of sample for whom vaccination data available, by year: all practices

	1997 n = 18162 63 practices1		1998 n = 17962 66 practices2		1999 n = 16254 66 practices		2000 n = 13762 62 practices3		In all years n = 10951 53 practices Age in 1997
	No	%	No	%	No	%	No	%	No	%
Male	6457	35.6	6339	35.3	5687	35.0	4797	34.8	3778	34.5
< 80 yrs	2773	15.3	2376	13.2	1612	9.9	672	5.1	1873	17.1
80–84 yrs	2231	12.3	2349	13.1	2377	14.6	2535	18.0	1298	11.9
>= 85 yrs	1453	8.0	1614	9.0	1698	10.4	1588	11.5	607	5.5
Median age		(80)		(81)		(82)		(82)		(80)
Female	14551	64.4	11623	64.7	10567	65.0	8967	65.2	7173	65.5
<80 yrs	4139	22.8	3503	19.5	2387	14.7	1015	7.4	2954	27.0
80–84 yrs	4041	22.2	4156	23.1	4089	25.2	4106	29.8	2517	23.0
>=85 yrs	3525	19.4	3964	22.1	4091	25.2	3846	28.0	1702	15.5
Median age		(82)		(82)		(83)		(84)		(81)
Deprivation quintile4
Least deprived	4567	25.2	4689	26.1	4287	26.4	3419	24.8	2587	23.6
2nd quintile	5479	30.2	5420	30.2	4933	30.4	3963	28.8	3290	30.0
3rd quintile	3822	21.0	3694	20.6	3336	20.5	3037	22.1	2399	21.9
4th quintile	2444	13.5	2432	13.5	2182	13.4	2000	14.5	1518	13.9
Most deprived	1850	10.2	1727	9.6	1516	9.3	1343	9.8	1157	10.6
Population density5
<250 pers km-2	6156	33.9	6116	34.0	5539	34.1	4509	32.8	3931	35.9
250–1000 pers km-2	4472	24.6	4336	24.1	3913	24.1	3652	26.5	2691	24.5
1000–2500 pers km-2	5074	27.9	4966	27.6	4511	27.8	3549	25.8	2602	23.8
>=2500 pers km-2	2460	13.5	2544	14.2	2291	14.1	2052	14.9	1727	15.8

1. 53 practices in all years plus 10 practices in years 1997–1999 2. 53 practices in all years plus 11 practices in years 1997–1999 plus 2 practices in 1998–2000 3. 53 practices in all years plus 7 practices in 2000 only plus 2 practices in 1998–2000 4. Quintiles defined according to distribution of Enumeration Districts in Britain 5. Population density smoothed over a 5-kilometre radius from the centroid of the Enumeration District