Table 2.

Effectiveness of influenza vaccines in HIV-infected patients

Study	Outcome Studied	Vaccine	Control	Risk Difference (95% C.I.)	NNV*	Vaccine effectiveness **
Tasker 1999 [26]	Symptoms of respiratory illness, at least 4 fold increase in antibody titre, viral culture	16/55	23/47	-0.198 (-0.387, -0.01)	5	41%
Fine 2001, [4]	Influenza like illness or a 4 fold increase in antibody titers or isolation of influenza virus	19/42	18/29	-0.168 (-0.404, -0.067)	6	27%
Raineri 2005, [34]	Influenza illness	12/90	34/55	-0.485 (-0.632, -0.337)	3	78%
Yamanaka 2005, [27]	Influenza like symptoms with at least 4 fold increase in antibody titre or viral isolation in culture	16/262	14/66	-0.151 (-0.255, -0.048)	7	71%

C.I.: Confidence Interval; NNV: * Number needed to vaccinate (= 1/RD); ** Vaccine effectiveness = 100*(1-risk ratio)