Abstract Title:

Shedding of Ann Arbor strain live attenuated influenza vaccine virus in children 6-59 months of age.

Abstract Source:

Vaccine. 2011 Apr 20. Epub 2011 Apr 20. PMID: 21513761

Abstract Author(s):

Raburn M Mallory, Tingting Yi, Christopher S Ambrose

Article Affiliation:

MedImmune, LLC, One MedImmune Way, Gaithersburg, MD 20878, USA.


BACKGROUND: A trivalent, Ann Arbor strain, live attenuated influenza vaccine (LAIV) is approved for use in children 24 months of age and older in a number of countries. The incidence, duration, and other parameters of viral shedding after vaccination with LAIV have not been fully described in children≤5 years of age. METHODS: An open-label, single-arm, multicenter, phase 2 study assessed viral shedding and safety in 200 children 6-59 months of age after a single, intranasal dose of LAIV in 2006. Participants were enrolled into 2 age groups: 6-23 months (n=100) and 24-59 months (n=100) of age.Viral shedding, reactogenicity, and adverse events were assessed for 28 days postvaccination. Serious adverse events and significant new medical conditions were monitored for 180 days postvaccination. RESULTS: Viral shedding was detected by culture in 79% (95% CI, 73-84) of vaccine recipients and occurred more frequently in children 6-23 months of age (89%) compared with children 24-59 months of age (69%). In total, 157 subjects shed vaccine, which was confirmed by RT-PCR as A/H1N1 for 128 subjects, A/H3N2 for 72 subjects, and B for 74 subjects. The incidence of shedding was highest on day 2 (59% in the 6-23 month age group; 41% in the 24-59 month age group) and most shedding occurred 1-11 days postvaccination; shedding after 11 days was infrequent and occurred almost exclusively in children 6-23 months of age. Mean titers of shed vaccine virus peaked on day 2 and were generally<10(3.0) median tissue culture infective dose/mL for both groups. Reactogenicity events peaked on day 2; runny/stuffy nose was reported most frequently (63% of all subjects). CONCLUSION: Most children 6-59 months of age vaccinated with Ann Arbor strain LAIV shed≥1 vaccine virus within 11 days of vaccination. Shedding was less common in children 24-59 months of age, a population for whom LAIV is approved for use. Titers of shed vaccine were low, which may explain why secondary transmission of LAIV was observed very infrequently in a previous controlled study conducted with young children in a daycare setting.

Study Type : Human Study

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