Abstract: The homology of PRRSV strain and China hp-PRRSV strain in some place was extremely high, in order to select the suitable vaccine for the region's disease and guide farmers to raise pigs, we selected the vaccines of hp-PRRS attenuated live vaccine (JXA1-R strain) and PRRS attenuated live vaccine (VR-2332 strain) as vaccine candidates, and selected 30 piglets, which was 30 d of age, good health, small group differences of weaned, randomly divided them into A, B and C groups, each group of 10 piglets.Group A was injected with hp-PRRS attenuated live vaccine (JXA1-R strain), group B was injected with PRRS attenuated live vaccine (VR-2332 strain), group C, the control group, was injected with saline as same measure as groups A and B.We collected blood before immune, and 14, 28, 42, 56, 70 and 84 d after immune, analyzed the immune response of two vaccines in this report by the method of determination of lymphocyte numbers, detection of virus nucleic acid and detection of antibody.The results showed that 42 d after immune, the lymphocyte numbers of A and B groups rose, and group A was 19.3×10⁹/L, group B was 16.7×10⁹/L, group C had been at the original level.Antibody positive aspects, 14 d after immune, group A was 80%, while group B was 60%, group C was 0;42 d, group A was 100%, while group B was 80%, group C was 0.The positive aspects of viral nucleic acid, 14 d after immune, group A as 90%, while group B was 100%, group C was 0;42 d, group A was 40%, group B was 70%, group C was 0;70 d, group A was 0, group B was 20%, group C was 0.Therefore, hp-PRRS attenuated live vaccine (JXA1-R strain) could induce quick immune response, immune antibodies, duration for long time, high titer, good stability, and existence time of attenuated vaccine poison in the body was short, time was fast, high security, immune to pigs in some place had superior effect.

Key words: porcine reproductive and respiratory syndrome attenuated live vaccines; JXA1-R strain; VR-2332 strain; virus persistence; antibody dynamic