. Author manuscript; available in PMC: 2008 Dec 17.

Published in final edited form as: J Am Stat Assoc. 2006 Mar;101(473):51–64. doi: 10.1198/016214505000000970

Table 1.

Basic Principal Stratification P₀ Based on the Potential Infection Outcomes (S(v), S(p)) With Potential Postinfection Strata Based on (Y(v), Y(p))

Potential infection strata		Potential postinfection strata
Basic principal stratum, S^P₀	Potential infection outcomes (S(v), S(p))	Potential postinfection outcomes (Y(v), Y(p))	Postinfection interpretation
Immune	(0, 0)	(, )	Always undefined
Harmed	(1, 0)	(0, *)	Not severe vaccine, undefined placebo
		(1, *)	Severe vaccine, undefined placebo
Protected	(0, 1)	(*, 0)	Undefined vaccine, not severe placebo
		(*, 1)	Undefined vaccine, severe placebo
Doomed	(1, 1)	(0, 0)	Never severe
		(1, 0)	Harmed by vaccine
		(0, 1)	Helped by vaccine
		(1, 1)	Always severe