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Haemagglutinin inhibition antibody geometric mean titres at pre-vaccination, Day 21, Day 42, and Month 12 in (A) Study A and (B) Study B (according to protocol cohort for persistence at Month 12). Footnote: 3–9 years age group = children in Study B, who received the first vaccine dose at 3–9 years of age, 10–17 years age group = children in Study B, who received the first vaccine dose at 10–17 years of age. Error bars represent 95% confidence intervals.
