This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunization, Subject name: Pediatrics
Salk vaccine is a: 
Select and explain. 
A. Live vaccine, B. Live attenuated vaccine, C. Killed vaccine, D. Toxoid
C: Killed vaccine
Answer: C: Killed vaccine 
Explanation: c. Killed vaccine(Ref: IAP Guidebook on Immunization 2013-14; pg 113-117, Nelson's 20/e p 3212, Ghai, 8/e p 190- 191)Polio vaccines were developed in the USA during 1950, first the inactivated polio vaccine (IPV) by Jonas Salk and later the live oral polio vaccine (OPV) by Albert Sabin. Remember: 'Salk' is a 'killed' vaccine.