1. Poliomyelitis. https://www.who.int/news-room/fact-sheets/detail/poliomyelitis [accessed on 08 June 2019].
2. Poliomyelitis. https://www.who.int/ith/vaccines/polio/en/ [accessed on 24 November 2018].
3. Considerations for the full global withdrawal of oral polio vaccine after eradication of polio;Hampton;J Infect Dis,2017
4. Rationale and timelines for OPV withdrawal. http://www.who.int/immunization/diseases/poliomyelitis/endgame_objective2/oral_polio_vaccine/planning/en/ [accessed on 24 November 2018].
5. SAGE confirms global polio vaccine switch date as April 2016. http://polioeradication.org/news-post/sage-confirms-global-polio-vaccine-switch-date-as-april-2016/ [accessed on 24 November 2018].