Objective: To find out the prevalence, efficacy and safety of SA-14-14-2 vaccine against Japanese Encephalitis (JE). Materials and Methods: A total of 60 children in the age group of 6 to 10 yrs, belonging to 5 schools in 5 blocks (12 from each) of Virudhunagar District of Tamilnadu were selected for vaccination. Three samples from each child, one sample prior to vaccination, second sample four weeks after vaccination and third sample twelve weeks after vaccination were taken. Pre and post vaccination samples were screened for antibodies to the JE virus by MAC ELISA and antibody titre was determined by Haemagglutination Inhibition (HAI) test. Results: Among the 60 pre vaccinated samples, only 2 (3.33%) showed IgM antibodies. Samples collected after 4 weeks and 12 weeks of vaccination, 24 (40.68%) and 58 (98.30%) showed sero conversion to JE respectively. The antibody titre of all the samples were determined by HAI technique. In the prevaccinated IgM positive samples, one male child from Pandalkudi Primary Health Centre (PHC), one female from Mallanginar PHC showed HAI titre of 1 in 160 confirming the presence of subclinical case prevalence in these two Blocks. The efficacy of the vaccine was proved by the seroconversion in the samples collected in all five blocks (PHC) at Virudhunagar by HAI Evaluation of safety of vaccine was analysed by noting the local irritation and systemic toxicity that occured after the vaccination and it was shown that swelling was present in 1 child (8.33%) in Narikudi, headache was present in 1 child (8.33%) in Pandalgudi. No cases of encephalitis / meningitis, seizure were detected in any block.