Varicella vaccine (live) powder and solvent for suspension for injection 0.5ml vials

BACKGROUND: This study provides a comprehensive review of studies comparing the effectiveness of varicella vaccinations and the duration of their protection. METHODS: We conducted a systematic literature review to identify comparative studies evaluating the effectiveness of the varicella vaccine. A meta-analysis was performed to assess the effectiveness of one-dose and two-dose vaccinations, as well as the outcomes for moderate and severe illness, and the duration of protection, using random effects models. RESULTS: Out of 66 studies, 57 reported the effectiveness of a single-dose varicella vaccine, 28 examined the two-dose vaccination, and 25 focused on effectiveness against moderate to severe disease. Of these, 59 were observational studies and 7 were trials. Thirteen studies reported the duration of protection. The overall vaccine effectiveness for a single dose was 79% (76-82%; I² = 97.2%), while for two doses, it was 94% (93-96%; I² = 90.8%). The overall effectiveness against moderate or severe illness was 92% (90-94%; I² = 90.3%). The duration of protection showed a slight decline over time. Evidence suggests that both one and two doses of the varicella vaccine offer short-term protection, though this protection wanes rapidly. CONCLUSION: The two-dose vaccination demonstrated superior clinical efficacy compared to the one-dose vaccination, with protection slightly diminishing over time. These findings highlight the importance of implementing universal two-dose varicella vaccination programs in countries. TRIAL REGISTRATION: PROSPERO Identifier: CRD42024589864.

Abstract licence: CC BY-NC

OBJECTIVES: This study aimed to synthesize existing evidence to compare the immunogenicity and safety of domestic and imported live-attenuated varicella vaccine (VarV) in healthy Chinese populations. METHODS: We searched PubMed, Web of Science, Embase, China National Knowledge Internet (CNKI), Wan Fang Database, and Chinese Biomedical Literature Service System (SinoMed) using predefined search terms to identify relevant studies. Retrieve all language articles up to March 15, 2024. Articles reported varicella vaccination in healthy Chinese populations were included. We calculated the pooled rates of seroconversions and adverse events using the random effects model and assessed the quality of each study using the modified Jadad Scale and Newcastle Ottawa Scale (NOS). Publication bias was evaluated using Egger's regression test. RESULTS: In our immunogenicity analysis, which included 16,655 Chinese individuals from 21 studies, the pooled seroconversion rate was 89% (95%CI: 86-91%) for domestic VarV and 93% (95%CI: 88-98%) for imported Varv, with no statistically significant difference. In our safety analysis, which included 29,696 Chinese individuals from 25 studies, the pooled rate of systemic reactions was higher for domestic Varv (11%, 95%CI: 10-13%) than for imported Varv (8%, 95%CI: 6-10%; P < 0.001), while the results for local reactions were the opposite (domestic Varv: 3%, 95%CI: 2-3%; imported Varv: 7%, 95%CI: 3-10%; P = 0.020). The results are based on pooled proportions rather than direct comparison. Egger's test suggested that publication bias was not negligible. CONCLUSIONS: Both domestic and imported varicella vaccines appear to be generally immunogenic and safe in healthy Chinese populations. However, due to limited and heterogeneous data on imported vaccines, further high-quality studies are needed to validate these comparative findings.

Abstract licence: CC BY-NC-ND

Objectives: The varicella vaccine (VarV) produced by Sinovac (Dalian) obtained World Health Organization (WHO) prequalification in November 2022. However, no direct comparative studies have been conducted between VarV and other WHO-prequalified varicella vaccines. The study aimed to assess the immunogenicity and safety of Sinovac’s VarV compared with Merck Sharp &amp; Dohme’s (MSD) VARIVAX® (Moorgate, London, UK) following a single dose administration. Methods: This Phase III, randomized, double-blind, active-controlled, non-inferiority trial was conducted in the Philippines. Healthy children aged 12 to 15 months were enrolled. Eligible participants were randomly assigned (1:1) to receive a single dose of varicella vaccine either manufactured by Sinovac (Test group) or MSD (Active control group). Immunogenicity was evaluated 6 weeks after vaccination by enzyme-linked immunosorbent assay (ELISA). The primary immunogenicity endpoint was seroresponse rate 6 weeks after vaccination. Seroresponse rate was defined as varicella-zoster virus (VZV) antibody concentration ≥ 10 mIU/mL in participants who were seronegative (antibody concentration &lt; 10 mIU/mL) at baseline. The secondary endpoint was the corresponding geometric mean concentration (GMC). Adverse events (AEs) and serious adverse events (SAEs) were monitored for 6 weeks after vaccination. Results: Among the 484 participants analyzed, the seroresponse rates 6 weeks after vaccination were 98.85% and 98.88% in the Test group and Active control group, respectively, with a difference of −0.03% (95% CI: −3.10%, 2.99%), which exceeded the predefined non-inferiority margin of −10%. The corresponding GMCs were 35.73 mIU/mL and 37.34 mIU/mL, respectively, with the ratio of 0.96 (95% CI: 0.86, 1.06), also exceeding the predefined non-inferiority margin of 0.67. Furthermore, the incidence of adverse reactions (ARs) in the Test group was lower than that in the Active control group (38.08% vs. 55.51%). Conclusions: Sinovac’s VarV demonstrated non-inferior immunogenicity to WHO-prequalified comparator vaccine (VARIVAX®) and favorable safety profile. These findings indicated that VarV (Sinovac, Beijing, China) met WHO standards for varicella vaccine evaluation, supporting its global use consideration.

Abstract licence: CC BY

Background: In recent years, breakthrough varicella cases among individuals who have received a single dose of varicella vaccine (VarV) have increased notably, suggesting that the long-term protection following a one-dose VarV regimen requires further investigation. This study aims to evaluate the immune persistence following a single dose of Sinovac VarV at 5 and 8 years post-vaccination. Methods: In this Phase 4, open-label, observational follow-up study, participants aged 1 to 12 years (referring to the age of vaccination) who had received a single dose of either Sinovac VarV or placebo in the previous phase 3 trial were enrolled in a 1:1 ratio. Blood samples were collected 5 years and 8 years post-vaccination to measure antibody levels against varicella using the fluorescent antibody to membrane antigen (FAMA) method. A total of 487 and 422 participants were included in the 5-year and 8-year immune persistence analyses, respectively. The endpoints comprised the seropositive rates (≥1:4 and ≥1:8) and the geometric mean titers (GMTs) of varicella antibodies at both 5 and 8 years following vaccination. Results: Varicella antibody levels declined from 30 days post vaccination but remained stable from 5 to 8 years. Five years after vaccination, the seropositive rates (≥1:4) of varicella antibody were 100% in the VarV group and 80.83% in the placebo group; for ≥1:8, the rates were 89.07% and 64.17%, respectively. The corresponding GMTs were 1:13.67 and 1:7.71, respectively. Eight years after vaccination, the seropositive rates (≥1:4) were 99.54% in the VarV group and 90.69% in the placebo group; for ≥1:8, they were 88.53% and 74.51%, with GMTs of 1:13.52 and 1:9.91, respectively. Eight years post-vaccination, the seropositive rates and antibody levels in the VarV group remained nearly the same as by 5 years. Conclusions: Sinovac VarV can confer good immune persistence for up to 8 years following a single dose of vaccination in children aged 1 to 12 years. However, given the declining trend in antibody levels over time, revaccination may be needed to maintain protective immunity.

Abstract licence: CC BY