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.