Using surveillance data to estimate pandemic vaccine effectiveness against laboratory confirmed influenza A(H1N1)2009 infection: two case-control studies, Spain, season 2009-2010

Table 2 Pandemic influenza vaccine effectiveness in the surveillance-based and cycEVA studies^a, season 2009-2010, Spain

		Surveillance-based study		cycEVA study
	Included population	N	PIVE % (95%CI^b)	N	PIVE % (95%CI^b)
Crude	All patients	1326	35 (-38; 73)	436	58 (-81; 95)
	▪ Delay onset-swabbing less than four days	1175	35 (-45; 74)	381	57(-87; 95)
	EU case definition	701	14 (-131; 72)	377	53 (-109; 95)
	▪ Delay onset-swabbing less than four days	627	5 (-161; 70)	336	64 (-104; 95)
Adjusted models	All patients
	▪ full model^c			301	75 (-293; 98)
	▪ SISSS covariates^d	993	62 (-5; 87)	351	65 (-221; 96)
	All patients and delay onset-swabbing less than four days
	▪ full model^c			258	77 (-296; 98)
	▪ SISSS covariates^d	853	58 (-21; 85)	302	67 (-211; 97)
	EU case definition
	▪ full model^c			255	71 (-402; 98)
	▪ SISSS covariates^d	644	41 (-95; 82)	299	59 (-300; 96)
	EU case definition and delay onset-swabbing less than four days
	▪ full model^c			231	72 (-290; 99)
	▪ SISSS covariates^d	568	48 (-110; 82)	263	68 (-215; 97)

^a Cases and controls recruited between week 48/2009 and week 8/2010 and with a delay symptom onset-swabbing less than eight days; ^b CI = confidence interval; ^c Adjusted for age group, sex, seasonal vaccination, chronic conditions, previous hospitalizations, number of GP visits in the previous year, functional status, smoking, previous influenza vaccination, risk factors for pandemic influenza, and month of swabbing; ^d Adjusted for age group, sex, seasonal vaccination, chronic conditions, pregnancy, and month of swabbing; SISSS = Spanish Influenza Sentinel Surveillance.

ISSN: 1471-2458