1. WHO . World health organization vaccination coverage cluster surveys; 2015.
2. WHO . Vaccine-preventable diseases and vaccines-2017 update. International travel and health; 2012. 1–63.
3. World Health Organization . Vaccine safety basics learning manual; 2013.
4. Advances and challenges for the expanded programme on immunization
5. Realist synthesis of the International theory and evidence on strategies to improve childhood vaccination in low-and middle-income countries: developing strategies for the Nigerian Healthcare system;Omoniyi;Int J Health Policy Manag,2020