Modified live porcine respiratory and reproductive syndrome virus
Product name or type*
The pig vaccines that contain live attenuated PRRSV and which are authorised for use in Ireland are as follows:
- Suvaxyn PRRS MLV lyophylisate and solvent for suspension for injection for pigs (EU/2/17/215/001-003); Zoetis Belgium SA.
- UNISTRAIN PRRS lyophilisate and solvent for suspension for injection for pigs (VPA 10846/013/001); Laboratorios Hipra S.A.
- Porcilis PRRS lyophilisate and solvent for suspension for injection for pigs (VPA 10996/128/001); Intervet Ireland Limited.
- ReproCyc PRRS EU lyophilisate and solvent for suspension for injection for pigs (VPA 10454/012/001); Boehringer Ingelheim Vetmedica GmbH.
- Ingelvac PRRSFLEX EU lyophilisate and solvent for suspension for injection for pigs (VPA 10454/008/001); Boehringer Ingelheim Vetmedica GmbH.
Veterinary practitioners, pharmacists and licensed merchants
Problem Or Issue:
Recombination between strains of PRRS virus, including live type 1 PRRSV vaccine strains, is a known, but rare phenomenon that has been reported previously in Denmark, where it has been associated with clinical signs of disease in PRRS-naïve herds. The circulation of PRRS viruses either from vaccine or field origin is considered to increase the likelihood of recombination. Fattening pigs and gilts appear to be particularly at risk as these animals often have insufficient immunity against PRRS. Following initial consideration of the matter, the EMA’s Committee for Veterinary Medicinal Products (CVMP) made the following recommendations:
- In order to limit the potential risk of recombination between vaccine strains, do not use different live attenuated PRRSV vaccines simultaneously or consecutively.
- Increased monitoring of any suspected adverse event relating to clinical signs of PRRS, including the occurrence of relevant clinical signs of the disease in vaccinated herds, is recommended. Any suspected adverse event should be reported to the national competent authority for veterinary medicines or the marketing authorisation holder. Clinical signs of PRRS include reduced fertility, increased rate of abortions, reduced appetite, increased piglet mortality and respiratory distress.
Following completion of the initial referral procedure in May 2020, the European Commission initiated a further review of all PRRS virus vaccines in July 2020 to address potential risk management measures that could be taken to limit the risk of recombination between PRRS viruses, including PRRS vaccine strains. In April 2021, the CVMP concluded its review and advised that:
The risk associated with recombination of a PRRS modified live vaccine strain with a PRRS field virus or between two PRRS MLV vaccine strains,
- The benefit-risk balance of modified live PRRS vaccines remains positive.
Implementation of strict external and internal biosecurity measures is recommended to decrease the transmission of PRRS field viruses and PRRS MLV vaccine strains between and within farms.
- and any potential adverse events resulting from it, is low.
- Modified live PRRSV vaccines continue to be an appropriate tool for the management of PRRSV infection/disease in Europe.
- In order to limit the potential risk of recombination between PRRS modified live vaccine (MLV) strains of the same genotype, do not use different PRRS MLV vaccines based on different strains of the same genotype on the same farm at the same time. In case of switching from one PRRS MLV vaccine to another, a transition period between both MLV vaccines should be respected. This period should preferably last longer than the shedding period of the previous used MLV vaccine.
Actions To Be Taken:
Veterinary practitioners should, where possible, avoid using live attenuated PRRSV vaccines from different manufacturers in animals in the same herd.
Veterinary practitioners should monitor for clinical signs of PRRS in vaccinated pig farms. Any suspected adverse events should be reported to the HPRA or the marketing authorisation holder for the vaccines involved.