Varicella Vaccine Effectiveness in Preventing Community Transmission in the 2-Dose Era

Abstract

Objectives We examined overall and incremental effectiveness of 2-dose varicella vaccination in preventing community transmission of varicella among children aged 4–18 years in two active surveillance sites. One-dose varicella vaccine effectiveness (VE) was examined in those aged 1–18 years. Methods From May 2009 through June 2011, varicella cases identified during active surveillance in Antelope Valley, CA and Philadelphia, PA were enrolled into a matched case-control study. Matched controls ±2 years of the incident case's age were selected from immunization registries. A standardized questionnaire was administered to participants' parents, and varicella vaccination history was obtained from healthcare provider, immunization registry, or parent records. We used conditional logistic regression to estimate varicella VE against clinically-diagnosed and laboratory-confirmed varicella. Results One hundred twenty-five clinically-diagnosed varicella cases and 408 matched controls were enrolled. Twenty-nine cases were laboratory-confirmed. One-dose VE (1-dose vs. unvaccinated) was 75.6% [95% confidence interval (CI): 38.7–90.3%] in preventing any clinically-diagnosed varicella and 78.1% (95% CI: 12.7–94.5%) against moderate/severe, clinically-diagnosed disease (≥50 lesions). Among subjects aged ≥4 years, 2-dose VE (2-dose vs. unvaccinated) was 93.6% (95% CI: 75.6–98.3%) against any varicella and 97.9% (95% CI: 83.0–99.7%) against moderate/severe varicella. Incremental effectiveness (2-dose vs. 1-dose) was 87.5% against clinically-diagnosed varicella and 97.3% against laboratory-confirmed varicella. Compared with 1-dose breakthrough cases, 2-dose cases had shorter duration of rash (P=0.01) and were 80% less likely to develop vesicular rashes (P=0.01). Conclusions Two-dose varicella vaccination offered improved protection against varicella from community transmission among school-aged children compared with 1-dose vaccination.

Varicella outbreak in a highly-vaccinated school population in Beijing, China during the voluntary two-dose era

“…However, outbreaks started by a two-dose breakthrough varicella have not been previously documented. Consistent with recent reports [12,13], the clinical presentation of two-dose breakthrough varicella in the current outbreak was generally mild, similar to one-dose breakthrough varicella [14]. This outbreak investigation reveals that breakthrough varicella in two-dose recipients are still contagious.…”

“…The findings further confirmed that children vaccinated with two doses of varicella vaccine may contract varicella, and moderate two-dose varicella vaccination coverage may not provide sufficiently high population immunity to prevent outbreaks [11]. This study also confirms previous reports that one- and two-dose varicella vaccination is highly effective at mitigating the severity of breakthrough disease and reducing attack rates [12–14]. …”

“…Clinical trial and several observational studies found increased varicella VE of 2-dose than 1-dose vaccination [12–14,16]. Our outbreak investigation and another one in the similar school setting in US [11] found no difference in 1- and 2-dose varicella VE.…”

A Highly Efficacious Herpes Simplex Virus 1 Vaccine Blocks Viral Pathogenesis and Prevents Corneal Immunopathology via Humoral Immunity

“…Efficacies of vaccine-mediated protection against infection are often proportional only to a certain reciprocal challenge dose threshold (48), as has been observed with breakthrough varicella (49). To further demonstrate the extent of immunologic protection elicited by the 0⌬NLS vaccine, immunized mice were challenged with a 100-fold-higher viral inoculum than that described above (50,000 PFU/cornea; 100ϫ LD 50 ) and assessed for sensitivity to infection (Fig.…”

Evaluation of Patients with Varicella Infection at a Tertiary Center after Application of Single Dose Varicella Vaccine According to National Immunization Program

“…Çalışmamızda olguların %62.5'inde enfekte bireyle temas öyküsü mevcuttu. Birçok ülkede VZV'ye karşı rutin aşılama programı uygulanmakta ve çalışmalarda aşılanmış olgularda hastalık şiddetinin ve suçiçeği ilişkili sağlık bakım hizmetlerinin azaldığı bildirilmektedir (7). Ayrıca aşılanmanın sağladığı toplumsal immünite sayesinde 12 ay altı süt çocuklar ile aşılanmamış ve duyarlı erişkinlerde hastalık görülme sık-lığı azalmaktadır (8).…”