Although several vaccines are available worldwide, we know that they do not provide full and universal protection against PRRS virus infection. As stated above, there are two main reasons behind this phenomenon:

1. The virus has high genetic diversity.
   
    
2. The virus strongly modulates the immune responses.
   
    

So… one question arises, are PRRS virus vaccines useful? The answer is quite simple: ABSOLUTELY YES.

Although vaccination does not necessarily provide full protection against the infection, it can reduce the impact of the disease.

1. Vaccines have beneficial effects in terms of clinical protection. 
   
    
2. Vaccines can reduce the proportion of viraemic pigs and the duration of the viraemia.
   
    
3. Vaccines can reduce PRRS virus shedding.
   
    
4. Therefore, vaccines can minimise the transmission of the virus.

In order to ensure the best results using the vaccination, two main factors need to be considered:

1. Combination of actions and measures are essential: management and biosecurity.
   
    
2. Time is needed to reach a minimum level of immunity.

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