Vaccines That Reduce Viral Shedding Do Not Prevent Transmission of H1N1 Pandemic 2009 Swine Influenza A Virus Infection to Unvaccinated Pigs
Helen Everett, Pauline M. van Diemen, Mario Aramouni, Andrew Ramsay, Vivien Coward, Vincent Pavot, Laëtitia Canini, Barbara Holzer, Sophie Morgan, Mark Woolhouse, Elma Tchilian, Sharon M. Brookes, Ian H. Brown, Bryan Charleston, Sarah C. Gilbert
Abstract
This study was designed to determine whether vaccination of pigs with conventional WIV or virus-vectored vaccines reduces pH1N1 swine influenza A virus shedding following challenge and can prevent transmission to naive in-contact animals. Even when viral shedding was significantly reduced following challenge, infection was transmissible to susceptible cohoused recipients. This knowledge is important to inform disease surveillance and control strategies and to determine the vaccine coverage required in a population, thereby defining disease moderation or herd protection. WIV or virus-vectored vaccines homologous to the challenge strain significantly reduced virus shedding from directly infected pigs, but vaccination did not completely prevent transmission to cohoused naive pigs.