Nasal shedding of vaccine viruses after immunization with a Russian‐backbone live attenuated influenza vaccine in India

• Published in: Influenza and other respiratory viruses Vol. 17; no. 6; pp. e13149 - n/a
• Main Authors: Dar, Lalit, Krishnan, Anand, Kumar, Ramesh, Dhakad, Shivram, Choudekar, Avinash, Bagga, Sumedha, Sharma, Amrit, Kumar, Amit, Jethani, Jyoti, Saha, Siddhartha, Amarchand, Ritvik, Kumar, Rakesh, Choudhary, Aashish, Narayan, Venkatesh Vinayak, Gopal, Giridara, Lafond, Kathryn E., Lindstrom, Stephen
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01-06-2023; John Wiley and Sons Inc
• Subjects: Child; developing countries; Effectiveness; Genes; Humans; Immunization; India; Influenza; Influenza A Virus, H1N1 Subtype; Influenza A Virus, H3N2 Subtype; Influenza Vaccines; live attenuated influenza vaccine; Low income groups; Original; pediatric; Polymerase chain reaction; Respiratory diseases; RNA-directed DNA polymerase; Strains (organisms); Temperature; Transport media; Vaccination; Vaccine efficacy; vaccine virus shedding; Vaccines; Vaccines, Attenuated; Viruses; India; Bangladesh; United States > US; Senegal; California; Ann Arbor Michigan; Union of Soviet Socialist Republics > USSR; influenza; live attenuated influenza vaccine; developing countries; vaccine virus shedding; pediatric
• ISSN: 1750-2640; 1750-2659; 1750-2659
• DOI: 10.1111/irv.13149

Background
We present post‐vaccination nasal shedding findings from the phase IV, community‐based, triple‐blinded RCT conducted to assess efficacy of trivalent LAIV and inactivated influenza vaccines in rural north India.
Methods
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.
Results
In year 1, on day 2 post‐vaccination, 71.2% (74/104) of LAIV recipients shed at least one of vaccine virus strains compared to 42.3% (44/104) on day 4. During year 1, on day 2 post‐vaccination, LAIV‐A(H1N1)pdm09 was detected in nasal swabs of 12% LAIV recipients, LAIV‐A(H3N2) in 41%, and LAIV‐B in 59%. In year 2, virus shedding was substantially lower; 29.6% (32/108) of LAIV recipients shed one of the vaccine virus strains on day 2 compared to 21.3% on day 4 (23/108).
Conclusion
At day 2 post‐vaccination in year 1, two‐thirds of LAIV recipients were shedding vaccine viruses. Shedding of vaccine viruses varied between strains and was lower in year 2. More research is needed to determine the reason for lower virus shedding and vaccine efficacy for LAIV‐A(H1N1)pdm09.