Objective:

To assess the correlation between vaccine-elicited hemagglutination-inhibition (HAI) antibodies and protection against influenza in children vaccinated with live attenuated influenza vaccines (LAIV) versus inactivated influenza vaccines (IIV), highlighting the significance of this comparison.

Key Findings:

• HAI titers were significantly associated with reduced risk of confirmed influenza for matched strains: A/H1N1 (29.6%), A/H3N2 (34.8%), and B/Yamagata (31.8%).
• No significant reduction in risk was observed for B/Yamagata-specific HAI titers in the 2012–2013 season, which should be clarified for its implications.
• Both LAIV3 and IIV3 elicited HAI antibodies that correlated with protection against influenza infection when strains matched.

Interpretation:

HAI titers serve as a reliable correlate of protection against influenza in children, regardless of the vaccine type used, particularly when the vaccine strains match circulating strains, with implications for vaccination strategies.

Limitations:

• The study was limited to specific influenza seasons and a single population group, which may affect generalizability and applicability to other populations.
• Lower HAI titers in the LAIV group may complicate direct comparisons with IIV.

Conclusion:

Both LAIV and IIV vaccines are effective in eliciting protective HAI antibodies in children, supporting the use of HAI as a correlate of protection in influenza vaccination strategies, emphasizing its broader relevance.