Abstract
BackgroundIn practice, field evaluation of vaccine efficacy in individual herds is often based on a historical comparison of productivity data following initiation of vaccination. Being biased by time, this study design highly contrasts the more controlled, parallel-group design used for most initial vaccine efficacy studies but offers the possibility of including a larger number of animals and herds. As an important add-on to previous findings in controlled studies, the objective of this study was to evaluate the field efficacy of the ready-to-use combination vaccine Porcilis® PCV M Hyo (MSD Animal Health) by an observational historical study design using routinely generated herd productivity data.ResultsData on mortality, average daily weight gain and feed conversion rate were collected as yearly averages for one year prior to and one year after implementation of Porcilis® PCV M Hyo vaccination from 20 nursery and 23 finishing herds. When comparing pre- and post-vaccination periods, the average improvements in productivity data amounted to − 0.4 percentage points for mortality (p = 0.014), + 5 g for average daily weight gain (p = 0.555) and − 0.06 feeding units(FU)/kg for feed conversion rate (p = 0.074) in nursery herds and − 0.5 percentage points for mortality (p = 0.012), + 34 g for average daily weight gain (p < 0.001) and − 0.04 FU/kg for feed conversion rate (p = 0.133) in finishing herds. Even though some nursery and finishing herds also previously vaccinated against PCV2 and/or Mycoplasma hyopneumoniae, this did not significantly affect the results. For finishers, these results were obtained when difference in arrival weights between the periods and shared ownership of the herds were additionally taken into account.ConclusionIn these 20 nursery and 23 finishing herds, previous findings from parallel-group vaccination studies concerning average daily weight gain for finishers were confirmed. Additionally, a significant effect on mortality for both nursery and finishing herds was demonstrated in this evaluation based on routinely generated herd productivity data.
Highlights
Field evaluation of vaccine efficacy in individual herds is often based on a historical comparison of productivity data following initiation of vaccination
No significant effect on mortality has been found in any of these studies, which could be speculated to be partly due to the Porcine circovirus type 2 (PCV2) infections being subclinical and partly due to the parallel study design allowing non-vaccinated pigs to benefit from vaccinated pigs and vice versa due to commingling
Mortality was significantly reduced by 0.4 percentage points, average daily weight gain increased non-significantly with 5 g and a tendency for reduced feed conversion rate was seen, amounting to 0.06 feeding units (FU)/kg
Summary
Field evaluation of vaccine efficacy in individual herds is often based on a historical comparison of productivity data following initiation of vaccination. No significant effect on mortality has been found in any of these studies, which could be speculated to be partly due to the PCV2 infections being subclinical (as in [1–5]) and partly due to the parallel study design allowing non-vaccinated pigs to benefit from vaccinated pigs (in terms of infectious pressure) and vice versa due to commingling [6] Usually, all pigs in a herd are either vaccinated or not, and individual-herd vaccine effect-evaluation is primarily based on whether the routinely generated herd productivity reports show improvements in mortality, average daily weight gain and/or feed conversion rate following implementation of a vaccination strategy Such a historical comparison has the obvious confounding effect of time, the impact of vaccination on i.e. productivity parameters is not compromised by the presence of non-vaccinated pigs, increasing the group infectious pressure. The objective of this study was to evaluate the field efficacy of Porcilis® PCV M Hyo in a larger number of herds by an observational historical study design using routinely generated data from individual herd productivity reports
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