Methods
COLD
Children aged 2–10 years received LAIV or intranasal placebo across 2015 and 2016, as per initial allocation. On days 2 and 4 post‐vaccination, trained study nurses collected nasal swabs from randomly selected subset of trial participants based on operational feasibility, accounting for 10.0% and 11.4% of enrolled participants in 2015 and 2016, respectively. Swabs were collected in viral transport medium and transported under cold chain to laboratory for testing by reverse transcriptase real‐time polymerase chain reaction.