High-dose quadrivalent influenza vaccine shows non-inferior immunogenicity in Chinese children aged 6 to 35 months

This was a randomized, double-blind clinical study conducted in China. The population consisted of 3,000 children aged 6 to 35 months. The study setting was China. The intervention was an investigational high-dose quadrivalent influenza vaccine (H-QIV). The comparators were an investigational low-dose quadrivalent influenza vaccine (LQIV-01) and a commercially available low-dose quadrivalent influenza vaccine (LQIV-02). The primary outcome was the non-inferiority of the investigational vaccines to the commercially available vaccine in immunogenicity. The follow-up period was 6 months.

The main results for immunogenicity showed that both investigational vaccines demonstrated non-inferiority to the commercially available vaccine. For hemagglutination inhibition (HI) antibody titers, H-QIV exhibited >11-fold increases compared to pre-vaccination levels against H1N1, H3N2, B/Yamagata, and B/Victoria strains. The seroprotection rates (SPRs) exceeded 95%. The seroconversion rates (SCRs) exceeded 89%. The immune response strength was superior for H-QIV compared to both L-QIVs.

Key secondary outcomes included the comparison of H-QIV to the low-dose investigational and commercial vaccines. The data showed H-QIV was superior in immune response strength. The study also reported hemagglutination inhibition (HI) antibody titers, with H-QIV showing >11-fold increases. Safety and tolerability were also key secondary outcomes.

Safety and tolerability findings indicated comparable safety profiles across all vaccine groups. The adverse event rates were comparable. Serious adverse events were not reported. Discontinuations due to adverse events were not reported. The tolerability was reported as comparable safety profiles.

These results can be compared to prior landmark studies in influenza vaccination. However, the specific prior studies are not reported in the input data. The current study provides evidence in a pediatric population in China, which may differ from previous studies conducted in other regions or age groups.

Key methodological limitations are not reported in the input data. Potential biases cannot be assessed from the provided information. The study was randomized and double-blind, which helps reduce bias, but the absence of reported limitations means the full context of potential biases is unknown.

For clinical practice, the results suggest that H-QIV can provide greater protection and benefits to this high-risk population of young children. However, the evidence is specific to the studied population and setting. Clinicians should interpret these findings within the context of the available data and consider them as part of the broader evidence base for influenza vaccination in children.

Unanswered questions remain regarding the long-term durability of the immune response beyond 6 months, the effectiveness in preventing clinical influenza disease, and the generalizability to other populations or regions. Further research is needed to address these gaps.