2. Guillain‐Barré syndrome.

Study	Influenza season	Vaccine	Population	Age	RR (95% CI)
Schonberger 1979	1976 to 1977	A/New Jersey/76 or A/New Jersey/76 and A/Victoria/75 swine vaccine	All the USA population	> 64 years	5.2 (3.9 to 7.0)
Kaplan 1982	1979 to 1980	Inactivated trivalent	All the USA population	> 18 years	0.6 (0.45 to 1.32)
Kaplan 1982	1980 to 1981	Inactivated trivalent	All the USA population	> 18 years	1.4 (0.80 to 1.76)
Lasky 1998	1992 to 1994	Inactivated trivalent	21 million	> 64 years	1.5 (0.7 to 3.3)

Key: CI = confidence interval; RR = risk ratio