With advances in medical science, the discovery of penicillin and vaccination programs, major infectious diseases were now a much reduced threat to public health, and the emergency use of Lawlor's Island as a quarantine station was falling rapidly. During the 1920s and 1930s, the cost of salaries, supplies, and services outweighed the benefits of quarantining minor infectious diseases on Lawlor's Island. Costs included telephone charges, uniforms and large quantities of drugs and medical supplies. Following the Paris International Sanitary Convention of 1926, the Canadian deputy minister of health decided in 1936 that it would cease to house quarantine patients on the island. However when smallpox was detected by Pier 21 medical staff in a steamship sailor in 1938, Lawlor Island to be used a final time to contain an outbreak. The sailors and infected medical staff were quarantined and treated on the island. In place of Lawlor's Island, the government used a quarantine space at the Pier 21 immigration terminal and created an isolation ward at the former Rockhead Prison in Halifax's North End in 1938.