1. WHO. The expanded programme on immunization. 2013. http://www.who.int/immunization/programmes_systems/supply_chain/benefits_of_immunization/en
2. WHO. Surveillance for vaccine preventable diseases. 2017. http://www.who.int/immunization/monitoring_surveillance/burden/VPDs/en
3. WHO. Diphtheria tetanus toxoid and pertussis (DTP3) by region. 2018. http://apps.who.int/immunization_monitoring/globalsummary/timeseries/tswucoveragebcg.html
4. Vaccine hesitancy