Table 8. Summary of Findings From 2-Dose Varicella Vaccination Clinical Trials.
| Author, (Year) | Study design | Outcomes and results | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Kuter et al. (2004) (36) |
Design: Randomized control trial Population: N=2,196 children age ≥12 months to 12 years n= 1,103 (1 dose of vaccine) (mean age 3.6 years range 1 year–12.9 years) n= 1,093 (2 doses of vaccine) (mean age 3.9 years range 1 year–12.9 years) (Oka/Merck Varivax®) Participants enrolled Dec. 1991–Jan. 1993 Setting: 18 multi-centre sites Inclusion criteria Healthy children 12 months to 12 years with no history of varicella and/or zoster Exclusion criteria Significant exposure to varicella or zoster (>1 hour of contact indoors) in the 4 weeks before entry into the study; received another vaccination within a month before or planning to receive another vaccine during the month after injection; or received any blood products during preceding 3 months. Also excluded if history of anaphylactoid reaction to neomycin, known immune deficiency or neoplastic disease or depressed immunity from disease or drugs Intervention: Administration of either 1 dose or 2 doses of vaccine (2nd dose three months after 1st) containing 2,900-9,000 PFUs of attenuated Oka/Merck Varivax® Outcomes analyzed: • Persistence of varicella antibodies (as measured by gpELISA, titers ≥ 5 considered positive) • Lab-confirmed varicella cases occurring >42 days post-vaccination (acute and convalescent titers were ≥200 gpELISA units/ml) • Suspect case if there was a 4-fold rise between acute and convalescent samples and at least one titer was between 50 and 199 gpELISA units/ml • Vaccine efficacy based on person-years at risk to calculate annual and cumulative breakthrough disease; only subjects actively followed as of March 2002 by questionnaire and/or annual blood sample contribute estimate Follow-up: 10 years of follow-up with measurements taken each year |
Variable | 1-dose regimen | 2-dose regimen | ||||||
| No. of varicella cases | 60 | 17 | ||||||||
| Median days duration of rash (range) | 4 (1–18) | 5 (1–14) | ||||||||
| Median of the daily maximum # of lesions (range) | 26 (2–272) | 20 (2–100) | ||||||||
| % with >50 lesions | 22.8 | 18.8 | ||||||||
| % with 1 or more vesicle | 77.2 | 68.8 | ||||||||
| Median of the daily maximum no. of vesicles (range) | 13 (1–272) | 5 (1–80) | ||||||||
| % with temperature ≥ 38.9○C, oral equivalent | 2.4 | 0 | ||||||||
|
Vaccine efficacy (1 dose vs. 2 doses) 94.4% (95% CI: 92.9-95.7), 98.3% (95% CI: 97.3-99.0) p<.001 Risk of developing varicella >42 days post-vaccination during 10-year period was 3.3 fold lower in children receiving 2 doses as opposed to one (p< .001) VE for prevention of varicella after household exposure (1 vs. 2 doses) 90.2% (95% CI: 83.7-96.7) vs. 96.4% (95% CI:92.4-100) p=0.112 Persistence of varicella antibody (gpELISA) 1 to 9 years post-vaccination | ||||||||||
| 1-dose regimen | 2-dose regimen (0 and 3 mos.) | |||||||||
| Time post-vaccination | N | Persistence rate (%) % | ≥5 gpELISA units/ml | GMT | N | Persistence rate (%) | % ≥5 gpELISA units/ml | GMT | ||
| 6 wk. | 881 | NA | 85.7 | 12.5 | 768 | NA | 99.6 | 142.6 | ||
| 1 yr. | 657 | 100 | 86.9 | 20.8 | 588 | 99.8 | 97.4 | 32.0 | ||
| 2 yr. | 384 | 100 | 90.9 | 23.6 | 318 | 100 | 95.0 | 24.6 | ||
| 3 yr. | 458 | 99.8 | 93.2 | 44.7 | 398 | 100 | 98.2 | 50.9 | ||
| 4 yr | 452 | 99.6 | 92.0 | 45.3 | 395 | 100 | 92.9 | 36.8 | ||
| 5 yr. | 400 | 100 | 95.5 | 50.3 | 376 | 100 | 98.1 | 44.3 | ||
| 6 yr. | 399 | 99.7 | 93.7 | 49.5 | 392 | 100 | 96.7 | 49.7 | ||
| 7 yr. | 424 | 100 | 94.3 | 54.2 | 392 | 100 | 96.2 | 54.2 | ||
| 8 yr. | 381 | 100 | 94.5 | 56.5 | 347 | 99.1 | 96.0 | 52.8 | ||
| 9 yr. | 277 | 99.6 | 95.3 | 57.8 | 237 | 99.6 | 97.0 | 61.0 | ||