Porcine Respiratory and Reproductive Syndrome Virus Vaccinology: a Review for Commercial Vaccines

Porcine Reproductive and Respiratory Syndrome (PRRS) since its appearance in Europe in the early 1990’s has resulted in tremendous economic losses. Under field conditions vaccination is one of the most efficient strategies for the prevention and control of PRRS. The aim of this study is to perform the PRRSV vaccinology regarding current status of commercial vaccines in Europe. There are two types of PRRSV commercial available vaccines in Europe: Killed Virus (KV) or inactivated vaccines and Modified-Live Virus (MLV) or attenuated vaccines. EU KV commercial vaccines provide limited efficacy due to the weak stimulation of the immune system and no effective induction of neutralizing antibodies. However, KV vaccines can induce a strong Cell Mediated Immune (CMI) response. One the other hand, commercial EU MLV vaccines provide effective strain-specific protection, only partial protection against genetically heterologous PRRSV and elicit relatively late humoral and CMI responses which lead to delayed protection. In Europe, the KV vaccination prove to reduce the negative effects of PRRSV in breeding herds, improving their reproductive performance, e.g., increase of farrowing rate and number of live or weaned pigs, reduction of premature farrowing rate, abortion rate and number of mummified and stillborn piglets. The use of commercial MLV vaccines in PRRSV-infected breeding herds leads to improvement of: (a) reproductive performance e.g., reduction of the abortion and return to oestrus rate and increase of the farrowing rate and number of weaners, ( b) the viraemic status, morbidity and mortality rate of piglets and (c) the growth performance of vaccinated pigs. In conclusion, nowadays the use of MLV or KV vaccines in Europe is the most economical tool to control the economic losses of PRRSV infection. However, the development of more efficacious PRRSV vaccines is the significant future goal for PRRSV vaccinology.