Sequential delivery of LAIV and SARS-CoV-2 in the ferret model can reduce SARS-CoV-2 shedding and does not result in enhanced lung pathology

Ryan, Kathryn A.; Schewe, Katarzyna E.; Crowe, Jonathan; Fotheringham, Susan A.; Hall, Yper; Humphreys, Richard; Marriott, Anthony C.; Paterson, Jemma; Rayner, Emma; Salguero, Francisco J.; Watson, Robert J.; Whittaker, Catherine J.; Carroll, Miles W.; Dibben, Oliver

Co-circulation of SARS-CoV-2 and influenza viruses could pose unpredictable risks to health systems globally, with recent studies suggesting more severe disease outcomes in co-infected patients. The lack of a readily available COVID-19 vaccine has reinforced the importance of influenza vaccine programmes during the COVID-19 pandemic. Live Attenuated Influenza Vaccine (LAIV) is an important tool in protecting against influenza, particularly in children. However, it is unknown whether LAIV administration might influence the outcomes of acute SARS-CoV-2 infection or disease. To investigate this, quadrivalent LAIV (QLAIV) was administered to ferrets 3 days pre- or post-SARS-CoV-2 infection. LAIV administration did not exacerbate SARS-CoV-2 disease course or lung pathology with either regimen. Additionally, LAIV administered prior to SARS-CoV-2 infection significantly reduced SARS-CoV-2 replication and shedding in the upper respiratory tract (URT). We conclude that LAIV administration in close proximity to SARS-CoV-2 infection does not exacerbate mild disease and can reduce SARS-CoV-2 shedding.