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Clin Infect Dis. 2019 Aug 13. pii: ciz719. doi: 10.1093/cid/ciz719. [Epub ahead of print] Viral Shedding in Recipients of Live Attenuated Influenza Vaccine in the 2016-2017 and 2017-2018 Influenza Seasons in the United Kingdom.
Jackson D1, Pitcher M1, Hudson C1, Andrews N2, Southern J3, Ellis J3, H?schler K1, Pebody R3, Turner PJ3,4, Miller E3, Zambon M1.
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1 Virus Reference Department, National Infection Service, Public Health England, Colindale, United Kingdom. 2 Statistics, Modelling and Economics Department, National Infection Service, Public Health England, Colindale, United Kingdom. 3 Immunisation and Countermeasures, National Infection Service, Public Health England, Colindale, United Kingdom. 4 Section of Paediatrics, Imperial College London, London, United Kingdom.
Abstract
BACKGROUND:
The (H1N1)pdm09 live attenuated influenza vaccine (LAIV) strain was changed for the 2017-2018 influenza season to improve viral fitness, following poor protection against (H1N1)pdm09 viruses in 2015-2016. We conducted LAIV virus shedding studies to assess the effect of this change.
METHODS:
Children aged 2-18 years were recruited to receive LAIV in the 2016-2017 (n = 641) and 2017-2018 (n = 362) influenza seasons. Viruses from nasal swabs taken 1, 3, and 6 days postvaccination were quantified by reverse-transcription polymerase chain reaction and area under the curve titers were determined. Presence and quantity of shedding were compared between strains and seasons with adjustment for age and prior LAIV (n = 436), inactivated seasonal vaccine (n = 100), or (H1N1)pdm09 vaccine (n = 166) receipt.
RESULTS:
(H1N1)pdm09 detection (positivity) in 2016-2017 and 2017-2018 (11.2% and 3.9%, respectively) was lower than that of H3N2 (19.7% and 18.7%, respectively) and B/Victoria (28.9% and 33.9%, respectively). (H1N1)pdm09 positivity was higher in 2016-2017 than 2017-2018 (P = .005), but within shedding-positive participants, the (H1N1)pdm09 titer increased in 2017-2018 (P = .02). H3N2 and influenza B titers were similar between seasons. Positivity declined with age, and prior vaccination reduced the likelihood of shedding influenza B but not (H1N1)pdm09.
CONCLUSIONS:
The (H1N1)pdm09 titer increased in 2017-2018, indicating more efficient virus replication in shedding-positive children than the 2016-2017 strain, although overall positivity was reduced. Age and vaccination history require consideration when correlating virus shedding and protection.
CLINICAL TRIALS REGISTRATION:
NCT02143882, NCT02866942, and NCT03104790.
? The Author(s) 2019. Published by Oxford University Press for the Infectious Diseases Society of America.
KEYWORDS:
LAIV; influenza; vaccine effectiveness; virus shedding
PMID: 31642899 DOI: 10.1093/cid/ciz719