title: Vaccination of influenza a virus decreases transmission rates in pigs.
abstract: Limited information is available on the transmission and spread of influenza virus in pig populations with differing immune statuses. In this study we assessed differences in transmission patterns and quantified the spread of a triple reassortant H1N1 influenza virus in naïve and vaccinated pig populations by estimating the reproduction ratio (R) of infection (i.e. the number of secondary infections caused by an infectious individual) using a deterministic Susceptible-Infectious-Recovered (SIR) model, fitted on experimental data. One hundred and ten pigs were distributed in ten isolated rooms as follows: (i) non-vaccinated (NV), (ii) vaccinated with a heterologous vaccine (HE), and (iii) vaccinated with a homologous inactivated vaccine (HO). The study was run with multiple replicates and for each replicate, an infected non-vaccinated pig was placed with 10 contact pigs for two weeks and transmission of influenza evaluated daily by analyzing individual nasal swabs by RT-PCR. A statistically significant difference between R estimates was observed between vaccinated and non-vaccinated pigs (p < 0.05). A statistically significant reduction in transmission was observed in the vaccinated groups where R (95%CI) was 1 (0.39-2.09) and 0 for the HE and the HO groups respectively, compared to an Ro value of 10.66 (6.57-16.46) in NV pigs (p < 0.05). Transmission in the HE group was delayed and variable when compared to the NV group and transmission could not be detected in the HO group. Results from this study indicate that influenza vaccines can be used to decrease susceptibility to influenza infection and decrease influenza transmission.
authors.affiliation: Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, 385 Animal Science/Veterinary Medicine building, 1988 Fitch Avenue, St Paul, MN 55108, USA. torr0033@umn.edu.
authors.forename: Anna
authors.initials: A
authors.lastname: Romagosa
authors.forename: Matt
authors.initials: M
authors.lastname: Allerson
authors.forename: Marie
authors.initials: M
authors.lastname: Gramer
authors.forename: Han Soo
authors.initials: HS
authors.lastname: Joo
authors.forename: John
authors.initials: J
authors.lastname: Deen
authors.forename: Susan
authors.initials: S
authors.lastname: Detmer
authors.forename: Montserrat
authors.initials: M
authors.lastname: Torremorell
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000627:therapeutic use*; D008168:Lung / Q000473:pathology / Q000821:virology; D009666:Nose / Q000821:virology; D009976:Orthomyxoviridae Infections / Q000635:transmission / Q000662:veterinary* / Q000821:virology; D016865:Reassortant Viruses / Q000276:immunology; D013552:Swine; D013553:Swine Diseases / Q000635:transmission* / Q000821:virology; D015164:Vaccines, Inactivated / Q000627:therapeutic use
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines; D015164:Vaccines, Inactivated