Pilot to evaluate the feasibility of measuring seasonal influenza vaccine effectiveness using surveillance platforms in Central-America, 2012

Table 2 Proportion of identified severe acute respiratory infections case-patients with complete information for selected variables, pilot case–control study for influenza vaccine effectiveness in Central-America, 2012 (n = 1,186)

	6 months − 11 years (n = 777)		≥60 years (n = 409)
	Influenza cases	Controls	Influenza cases	Controls
	n = 212	n = 565	n = 130	n = 279
Age	100 %	100 %	100 %	100 %
Gender	100 %	100 %	100 %	100 %
Clinical information
Date of onset of illness	100 %	100 %	100 %	100 %
Date of specimen collection	92 %	95 %	95 %	100 %
Preexisting conditions (yes/no)	67 %	61 %	88 %	87 %
Vaccination information
Vaccination status for current influenza vaccine^a	88 %	88 %	82 %	91 %
Date of current influenza vaccine receipt	100 %	100 %	100 %	100 %
Vaccination status for a second annual dose among children 6 months–9 years^b	67 % (121/193)	57 % (289/503)	NA^c	NA
Prior season influenza vaccination	96 %	96 %	84 %	94 %
Pneumococcal vaccination status^d	80 %	86 %	34 %	19 %
Number of complete records for key variables for vaccine effectiveness analyses^e	170 (80 %)	471 (83 %)	100 (77 %)	253 (91 %)
Number of complete records for all variables collected^f	151 (71 %)	458 (81 %)	34 (26 %)	51 (18 %)

^aFor receipt of at least one dose among children and older adults and after active/enhanced vaccination status ascertainment
^bWHO recommends 2 doses among children 6 months–9 years vaccinated for the first time
^cNA = Not applicable
^dVaccination up-to-date (yes/no) according to local recommendations
^eDefined as age, gender, dates of onset of symptoms and specimen collection, current vaccine status and date, presence of at least one preexisting condition, and country
^fKey variables, pneumococcal vaccination and prior influenza vaccination

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