Vaccination with a genotype 1 modified live vaccine against porcine reproductive and respiratory syndrome virus significantly reduces viremia, viral shedding and transmission of the virus in a quasi-natural experimental model

Efficacy and safety of simultaneous vaccination with two modified live virus vaccines against porcine reproductive and respiratory syndrome virus types 1 and 2 in pigs

“…There was no clear difference between single and dual vaccinated pigs in the response to challenge with PRRSV-1 virus. Some studies have found similar incomplete effect of vaccination following challenge of PRRSV-1 vaccinated pigs with heterologous PRRSV-1 strains [17,26], while others have found significant reduction in viremia following PRRSV-1 vaccination in a quasi-natural experimental model [27] and clinical protection in the field despite the field strain was only 85% identical to the vaccine strain in ORF 5 [19]. In the present study, vaccination against PRRSV-1 did not protect against challenge with Type 2 virus which are in accordance with the majority of previous studies [26,[28][29][30].…”

A commercial PCV2a-based vaccine significantly reduces PCV2b transmission in experimental conditions

“…Quantitative evaluation of a vaccine efficacy on reducing transmission of an infectious agent has often been evaluated in experimental conditions setting up transmission experiments as for example Aujeszky disease virus [30], Actinobacillus pleuropneumoniae [31] or PRRS virus [26,[32][33][34].…”

Porcine reproductive and respiratory syndrome virus (PRRSv) modified-live vaccine reduces virus transmission in experimental conditions

“…Quantitative evaluation of a vaccine efficacy on reducing transmission of an infectious agent has often been evaluated in experimental conditions setting up transmission experiments as for example Aujeszky disease virus [16], Actinobacillus pleuropneumoniae [17] or PRRS virus [10][11][12]. In Nodelijk's study, the authors used a modified-live vaccine based on a genotype 2 strain and challenged the pigs with a genotype 1 strain (Lelystad reference strain).…”

“…The total length of the experiment was also relatively short compared with the long shedding duration for PRRSv. In a recently published experiment [12], piglets were also followed for a relatively short period of time (21 days after contact with the seeder pig) as compared with the expected duration of PRRSv viraemia. Once PRRSv was introduced into the contact vaccinated or nonvaccinated groups by a non-vaccinated inoculated seeder pig, the observed numbers of contact-infected pigs were lower in the vaccinated groups than in the non-vaccinated ones.…”

“…No significant reduction of virus transmission in vaccinated animals has been shown although viraemia in those animals was significantly reduced in comparison with the non vaccinated ones [10,11]. Very recently, an experimental trial showed that vaccination with a genotype 1 modified-live vaccine could reduce transmission of a heterologous genotype 1 strain when introduced by a non-vaccinated inoculated seeder pig in the vaccinated group [12]. Although secondary cases caused by infectious vaccinated pigs could not be formally distinguished from cases due to contacts with the non vaccinated seeder pigs, this study showed a reduction in duration of shedding and transmission in the vaccinated groups.…”