Vaccination of influenza a virus decreases transmission rates in pigs

Romagosa, Anna; Allerson, Matt; Gramer, Marie; Joo, Han Soo; Deen, John; Detmer, Susan; Torremorell, Montserrat

In conclusion, transmission parameter estimates derived from this study can be used to further understand influenza transmission dynamics in naïve and immune swine populations. In our study, transmission to contact pigs was significantly reduced by vaccination but it could not be completely prevented when a heterologous vaccine was used. Virus transmission and replication was delayed and variable in the heterologous vaccinated group. On the other hand, transmission could not be detected in homologous vaccinated pigs. In the heterologous vaccinated group, active transmission took place even in the absence of clinical signs and presence of immunity, resulting in the silent spread of influenza virus which may contribute to the establishment of enzootic infected populations and increased probabilities of transmission to other herds. Such populations can in turn also be a risk for interspecies transmission and zoonotic infections. The results of the present study support field observations regarding the variability observed with influenza vaccines to affect transmission and spread of influenza virus.