Table A2.

Estimated seasonal vaccine efficacy in adults.

	Average Efficacy (Studies Used to Compute Average) ${}^{\mathit{a}}$
Season	H3N2	H1N1	B
2005–2006	49.4 (12.7,70.7) [84]	–	–
2006–2007	55.9 (35.5,70.4) [20,84]	–	–
2007–2008	58.3 (40.9,66.9) [22,23,85]	81.5 (60.9) [85]	45.8 (21.2, 59.2) [23,85]
2008–2009	–	62.3 (48.1, 72.6) [19,21]	60.1 (9.5, 82.4) [19]
Average	54.7 (41.8, 64.3)	73.6 (60.3, 77.5)	53.5 (27.0, 69.9)

${}^a$ Seasonal averages are calculated using arithmetic means of log RRs (Equation (A7)) reported by studies listed in Table A1. When subtype or type-specific efficacy is not explicitly measured, the efficacy against the dominant type/subtype in the study population is estimated as equal to the overall efficacy.