Frey 2002a.

Methods	Generation of allocation sequence: not described Allocation concealment: unclear Blinding: single (participants) Inclusion of all randomized participants: adequate; see 'Participants' Length of follow up: 56 days
Participants	Number: 680 enrolled and vaccinated; 665 developed a positive reaction ("take") at vaccination site and this number (665) used in trial report as denominator of analysis of adverse events Inclusion criteria: healthy adults aged 18 to 32 years Exclusion criteria: vaccinia scar; vaccinia vaccination; human immunodeficiency virus (HIV)‐AB; vaccination contraindications according to package insert (ie pregnancy, immunosuppression, and eczema), and protocol‐specified (history of live‐attenuated virus vaccination within 60 days before trial, receipt of blood products or immunoglobulin within 6 months before trial, household contact, sexual contact, or occupational exposure to someone with 1 or more of exclusion criteria listed in package insert); contact with infants < 12 months
Interventions	Dryvax smallpox vaccine: 1. Undiluted (108.1 plaque‐forming units (PFU)/mL) 2. Dilution 1:5 3. Dilution 1:10
Outcomes	1. Success rate 2. Humoral response (60% PFU reduction) and cellular response 3. Adverse events
Notes	Location: USA