Efficacy of bovine brucellosis vaccines: conceptions, challenges and meta-analysis. Response to the Letter to the Editor concerning -Efficacy of Brucella abortus S19 and RB51 vaccine strains: A systematic review and meta-analysis- by Blasco et al (Transbound Emerg Dis; 2021: https://doi.org/10.1111/tbed.14259) Documento