Comparison of response rates on invitation mode of a web-based survey on influenza vaccine adverse events among healthcare workers: a pilot study

Table 1 Comparison of response rates by invitation mode, age group and sex

	Total		Email invitation		Postal invitation		p-value
	Number sent	Response rate^a	Number sent	Response rate^a	Number sent	Response rate^a	Email vs post
Overall	1328	30.2	649	34.8	679	25.8	< 0.001
Age group^b
18–34 yrs	202	17.8	101	23.8	101	11.9	0.03
35–49 yrs	504	25.4	243	34.2	261	17.2	< 0.001
50–64 yrs	475	36.4	230	40.0	245	33.1	0.12
≥ 65 yrs	131	48.1	65	40.0	66	56.1	0.07
p-value (trend)		< 0.001		0.01		< 0.001
Sex^c
Female	1063	29.9	509	36.0	554	24.4	< 0.001
Male	263	31.6	138	31.2	125	32.0	0.88
Age and sex^b,c
Female 18–49 yrs	564	23.6	268	32.1	296	15.9	< 0.001
Male 18–49 yrs	140	22.1	74	28.4	66	15.2	0.06
Female ≥50 yrs	489	37.8	236	41.1	253	34.8	0.15
Male ≥50 yrs	117	43.6	59	35.6	58	51.7	0.08

vs: versus; yrs.: years
^aAAPOR response rate2 (number completed + number partial completes/sample size)
^b16 respondents had no data for age
^c2 respondents had no data for sex