Long term epidemiological effect of the vaccination with Porcilis PRRS in a sow herd

A study carried out in pigs suffering from reproductive problems showed that vaccination was effective for the long term control of PRRS.


The study was performed in a farrow to finish herd reared under intensive conditions.

In Spring 2002 an outbreak of late term abortions, increased still births and weak born piglets was noted. Serology tests detected the active circulation of PRRSV amongst sows and litters.

The sow herd was vaccinated with Porcilis PRRS:

  • 2 vaccinations 4 weeks apart
  • One month after the second vaccination the sows were revaccinated according to a 5/50 scheme (5 days of lactation and 50 days of pregnancy) with the same vaccine.

Replacement gilts were vaccinated with two vaccinations 4 weeks apart. The second vaccination was administered at least 4 weeks before entering the reproductive herd.

The herd was monitored for 16 months after introduction of the vaccine.

Parameters selected to determine long term efficacy were:

  1. Percentage of abortions during the monitoring period
  2. Incidence of PRRSV virus infections in the weaners at the end of the monitoring period.


  1. The abortion rate returned to its former level and was maintained until the end of the monitoring period. See Graph 1.
  2. PRRSV negative weaners were produced by 2x vaccinated sows up to 16 months after vaccination. See Graph 2.
Evolution of abortion rate

Graph 1: Evolution of the incidence of abortions from January 2002 to October 2003.

S/P ratio in piglets

Graph 2: Results of the S/P ratio in piglets

Graph 2 confirms that the production of PRRS negative weaners that was detected in piglets from two times vaccinated sows, was maintained at 16 months after the introduction of the vaccine in the farm. The fact that the pigs were still seroconverting in the fattening units could be considered as indicating point of a horizontal PRRS virus transmission from older fatteners to youngers ones.


Vaccination of sows with Porcilis PRRS is an effective measure for the long term control of PRRS.