A quantitative assessment of the effectiveness of PRRSV vaccination in pigs under experimental conditions

This paper presents a quantitative approach to evaluate effectiveness of va ccination under experimental conditions. We used two consecutive experiment al designs to investigate whether PRRSV transmission among vaccinated pigs was reduced compared to control pigs and to estimate the reproduction param eter R, Based upon data analysis and power calculations the series of small -scale vaccination-challenge experiments ended with multiple one-to-one exp eriments. This new experimental design has considerable power to detect the effect of vaccination on transmission if R is close to but still above one in vaccinated pigs. The last experiment showed that transmission was not s ignificantly reduced and the R for vaccinated pigs was estimated to be larg er than 4.9. This is remarkable because duration and level of viremia were significantly reduced by vaccination. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.