Immunogenicity and safety of varicella vaccine co-administered with seasonal influenza vaccine in healthy children aged 7-12 years in China

Abstract

Objectives: Varicella and influenza are major causes of morbidity in Chinese schoolchildren, with frequent outbreaks as varicella vaccination is not nationally included. Co-administration may improve coverage, but evidence in 7-12-year-olds is scarce. We assessed its immunogenicity and safety vs separate administration.

Methods: An open-label, randomized, controlled trial in Jiangsu included 899 healthy children (no varicella history) randomized 1:1:1 to varicella vaccine alone, influenza vaccine alone, or both. Immunogenicity was tested via fluorescent antibody to membrane antigen (varicella) and hemagglutination inhibition (influenza) at baseline and Day 30; safety was monitored for 30 days.

Results: For varicella, postvaccination geometric mean titers (GMTs) were 63.82 (VarV) vs 66.67 (co-administration; GMT ratio 1.04, 95% confidence interval 0.86-1.26), seropositivity rates ≥98.4%, and seroconversion rates ∼90% (both P > 0.05). For influenza, all strains met noninferiority: H1N1 GMT 993.36 (TIV) vs 1053.87 (co-administration), seroconversion ∼94%; H3N2/B/Victoria seropositivity ≥94.5%, seroconversion 72-94%. Overall, 8.35% had adverse events (vaccine-related 3.67%), mostly mild local reactions (e.g., injection-site pain), with 0.45% fever, hypersensitivity (0.11%), body pain (0.11%), and diarrhea (0.11%), and no vaccine-related serious events.

Conclusion: Concomitant varicella and influenza vaccination in 7-12-year-olds is immunogenically noninferior to separate use and well-tolerated, supporting integrated immunization strategies.

Keywords: Co-administration; Immunogenicity; Influenza vaccine; Safety; Varicella vaccine.