Technical Abstract: We investigated the ability of a Salmonella enterica serovar Typhimurium (S. typhimurium) aroA vaccine (ST-AV) to prevent egg contamination in chickens after oral challenge with S. enteritidis. Immunized birds had fewer positive ovary/oviduct pools and lower CFU/gram cecal contents of S. enteritidis than did non-immunized birds. However, the number of positive intestinal (duodenum, jejunum, ileum) and organ (spleen, kidney, liver) pools following challenge were nearly the same for immunized and non-immunized birds. Most importantly, aroA vaccinated birds produced more contaminated egg pools than did vaccinates. Humoral immune responses as measured by ELISA with LPS from each serovar as primary antigen detected significantly higher levels of circulating antibodies in vaccinates, but the response was not serotype specific. These results suggest that heterologous aroA vaccines might not be effective for reducing egg contamination by S. enteritidis even when the reproductive tract yields fewer CFU. Most importantly, results strongly suggest that GE-MLVs should be tested for their ability to decrease egg contamination directly if they are to be marketed to the layer industry.