Influenza A virus shedding reduction observed at 12 weeks post‐vaccination when newborn pigs are administered live‐attenuated influenza virus vaccine

BACKGROUND: Influenza A virus in swine (IAV‐S) causes an acute respiratory disease of swine which results in great economic losses. A bivalent H1N1 and H3N2, NS1‐truncated live‐attenuated IAV‐S vaccine (LAIV, Ingelvac Provenza(™)) has recently become available. OBJECTIVE: Reduction of shedding during an outbreak in the nursery or finisher is an important parameter from an epidemiological control strategy; therefore, a laboratory efficacy study was conducted to evaluate nasal virus shedding when vaccinated pigs were challenged with either heterologous H1N2 or H3N2 strains 12 weeks post‐vaccination. METHODS: Between 1 and 5 days of age, pigs born to IAV‐S seronegative dams were intranasally administered 1 mL of vaccine or saline. At 30 days post‐vaccination, pigs were weaned and randomized into two different challenge groups consisting of vaccinated pigs and control pigs commingled within pens for the two challenge groups. At 85 days post‐vaccination, pigs in the first group were challenged with A/Swine/North Carolina/001169/2006 H1N2 challenge strain, and the second group was challenged with A/Swine/Nebraska/97901‐10/2008 H3N2. Nasal swabs were collected daily for five days and tested by virus isolation. RESULTS AND CONCLUSION: This study showed significant reduction in nasal virus shedding with regard to both frequency and duration. A 1 mL intranasal dose of Ingelvac Provenza(™) given as early as 1 day of age showed protection for at least 12 weeks later as evidenced by the reduction of shedding live, viable virus after challenge with either a heterologous H1N2 strain or a heterologous H3N2 strain.