Table 2.

Statistical Power of the Binomial-based Maximized Sequential Probability Ratio Test for Different Adverse Events and True Relative Risks, Vaccine Safety Datalink Project, 2007/08

Adverse Event Category	No. of Days in Control Period	No. of Days in Risk Period	Age Groupa	Prespecified Upper Limit of No. of Events	Rangeb of Statistical Power for α = 0.01, %
					To Detect RR = 1.5	To Detect RR = 2.0	To Detect RR = 5.0
Seizure	8	8	Children	200	18–45	64–96	>99–100
			Adults	500	57–92	99–>99	100
Meningoencephalitis	60	21	All ages	150	12–28	47–84	>99–100
Bell's palsy	60	42	Children	50	4–10	14–34	78–>99
			Adults	1,000	92–>99	100	100
Other cranial nerve disorder	60	42	Children	25	2–5	6–15	35–77
			Adults	1,200	96–>99	100	100
Demyelinating disease	60	42	Children	15	2–4	4–11	22–62
			Adults	800	83–>99	>99–100	100
Disorder of the peripheral nervous system	60	42	Children	80	6–15	23–56	97–100
			Adults	2,000	>99–100	100	100
Ataxia	60	42	All ages	80	6–15	23–56	97–100
Allergic reaction other than anaphylaxis	2	2	Children	200	18–45	64–96	>99–100
			Adults	400	44–84	96–>99	100

Abbreviation: RR, relative risk.

^aAge groups: all ages, ≥6 months; children, 6 months–17 years; adults, ≥18 years.

^bBecause the upper limit is not always reached, the exact power is unknown. Assuming that at least half of the upper limit is reached, the statistical power to detect a signal is within the ranges shown.