Mixed treatment comparison meta-analysis of porcine circovirus type 2 (PCV2) vaccines used in piglets

https://doi.org/10.1016/j.prevetmed.2014.10.006Get rights and content

Highlights

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    All PCV2 vaccines are likely associated with increased ADG from wean to finish in swine.

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    The Suvaxyn® PCV/Fostera product was associated with the lowest estimate of ADG and a greatest uncertainty.

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    Circovac® shows a high gain with large uncertainty.

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    The data suggested few differences between the Circumvent® PCV and Ingelvac® CircoFLEXproducts with respect to ADG from wean to finish.

Abstract

Porcine circovirus type 2 (PCV2) vaccination is globally one of the most commonly used intervention strategies in growing pigs since several products became commercially available in 2006. While multiple trials have described the efficacy of individual PCV2 vaccines relative to non-vaccination, few studies provide product-to-product comparisons of efficacy. Given the well-documented efficacy of PCV2 vaccines, information about the comparative efficacy of available vaccines is more relevant to producers and veterinarians than comparison to non-vaccination. The objective of this study was to provide comparative estimates of changes in average daily gain effect associated with the use of the commercially available PCV2 vaccines. PubMed, CAB Abstracts, AGRICOLA, the USA Department of Agriculture Center for Veterinary Biologics database of licenses and provisions, and the proceedings of the Annual Meeting of the American Association of Swine Veterinarians, the Allen D. Leman Swine Conference, the Iowa State University Swine Disease Conference for Swine Practitioners, and the International Pig Veterinary Society Congress were used as the sources of information. Trials of licensed PCV2 vaccines administered according to manufacturers’ specifications to intensively raised piglets with a known herd porcine reproductive and respiratory syndrome virus (PRRSV) status were considered relevant to the meta-analysis. Relevant studies had to report average daily gain (ADG) from weaning to finish and PCV2 infection had to be naturally occurring.

Introduction

Vaccination against porcine circovirus type 2 (PCV2) is a common method to protect growing pigs against clinical disease manifestations associated with PCV2 infection commonly referred to as porcine circovirus associated disease (PCVAD) (Opriessnig et al., 2007). Four vaccines are labeled for use in piglets. These vaccines are marketed around the world using various names presented in Table 1. In the USA, the names are Fostera™ PCV (Zoetis Animal Health, New York, NY), a reformulated version of the discontinued Suvaxyn® PCV (Fort Dodge Animal Health, Fort Dodge, IA), Ingelvac® CircoFLEX™ (Boehringer Ingelheim Vetmedica, St. Joseph, MO), Circumvent® PCV (Merck Animal Health, Omaha, NE) and Circovac® (Merial Limited, Duluth, GA). For all these products, available data suggest improved production and health outcomes as compared to non-vaccinated animals. Consequently, PCV2 vaccines are widely used. Given the efficacy of all the products compared to no vaccination, the comparative efficacy of PCV2 vaccines is of interest to producers and veterinarians, as the choice to be made is likely among vaccines rather than a choice between vaccination and non-vaccination. Ideally, a large number of randomized controlled trials that compare the vaccines would be available to enable both producers and veterinarians to make a scientifically based comparison of vaccines in the same setting. However, to the authors’ knowledge, no trials directly comparing all the vaccines are publicly available. Given this paucity of direct evidence, it can be useful to include information from other comparisons in the evidence network. In this review, we use a mixed treatment comparison meta-analysis (MTC) to use direct and indirect evidence to compare the PCV2 vaccines (Dias et al., 2011a). Therefore primary objective of this meta-analysis was to compare the efficacy of commercially available PCV2 vaccines when used in intensively raised piglets. As a secondary analysis we assessed the effect of using the sample size as a measure of precision in an MTC meta-analysis when information about variation was missing.

Section snippets

Protocol and registration

An a priori protocol is not publicly available as mechanisms for registration were not available at the time the review was conducted. The a priori protocol describing the review question and the scope of the review was prepared by KA, AOC, and TO. The protocol was modified after the search and during data extraction. The changes to the eligibility criteria were (1) exclusion of studies that reported group-level allocation, and (2) more explicit criteria for reporting of results into the

Study selection

280 citations were identified by the searches after duplicates were eliminated. The first level of screening identified 32 potentially eligible citations. After the second level of screening 17 publications reporting 20 trials were included. The reasons for exclusion are presented in Table 2.

Study characteristics and results of individual studies

The interventions used, the ADG (SEM) and the number of animals per trials arm for each study in the meta-analysis are reported in Table 3.

Risk of bias within studies

Table 4 shows the information about the reporting of randomization

Summary of evidence

The objective of this MTC meta-analysis was to utilize publicly available data on commercial PCV2 vaccines used in piglets to provide a product-to-product comparison of impact on ADG. The results of the meta-analysis suggest that all products were associated with increased ADG compared to no vaccine. For example, the comparison of Circumvent® PCV to the control group suggested a 95% credibility interval for the mean ADG from 14 g/day to 38 g/day. The Ingelvac® CircoFLEX™ product had a very

Authorship

Primary author N. da Silva had chief responsibility for outcome result extraction and statistical analysis. Contributing authors are listed in alphabetical order. K. O’Neil conducted the search, screening for relevant abstracts and data extraction of population and intervention information. A. Carriquiry had an advisory role for statistical analysis and interpretation of model results. T. Opriessnig had an advisory role for vaccine information and interpretation of model results.

Disclosure

The authors affirm that this manuscript is an honest, accurate, and transparent account of the review being reported; no important aspects of the review have been omitted; and any discrepancies from the review as planned have been documented and explained.

Funding

No external funding was provided for this study.

Conflicts of interest

T. Opriessnig has received funding for vaccine research from Boehringer Ingelheim Vetmedica, Inc., Pfizer Animal Health/Zoetis, and Fort Dodge Animal Health. Rest of the authors has no conflicts of interest to declare.

Acknowledgments

Thank you to Dr. Dinkelman for guidance designing the search and P. Gerber for assistance in conducting the search.

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