In this research, White spot syndrome virus (WSSV) with 105.4LD50.mL-1 inactivated with gamma irradiation at a dose rate of 14-15 kGy.sec-1 was used as a vaccine. Three hundred and sixty shrimp of Litopenaeus vannamei, medium body weight (MBW) 1.0±0.17g), were prepared and experimentally exposed. They were distributed among four groups, inclusing vaccinated-virus exposed (T1), vaccinated-nonvirus exposed (T2), virus exposed (Positive control as T3) and non-vaccinated-non-virus exposed (Negative control as T4). The mortality percent of T1 started from day 5 and reached the highest (50%) on day 11 and remained constant until end of the experiment. In T2, no mortality was observed until the 3rd day and the maximum mortality (20%) was observed on day 9. On the other hand, no remarkable mortality was recorded for T4 unlike T3 in which the mortality started on day 2 and stopped on day 7. The minimum density of hyalinocyte was calculated in T4 but the maximum one was found in T3 (17.77±0.33) with no significant differences (p < /em><0.05) compared to T2 (16.59±0.96). A significant difference (p < /em><0.05) was observed between the values of Total Haemocyte Count (THC) before and after exposing to virus in T1. Total Protein Plasma (TPP) decreased to 29.03±3.41, while it was higher than 25.96±2.75 in T3 after 7 days. Such results might be responsible for developing resistance against WSSV in gamma irradiant vaccine in L. vannamei in comparison to T3 while the cause of mortality in T2 could be due to the lower effectiveness.