Table 2.

Implementation challenges and the impact of pediatric vaccine switches by themes.

Vaccine implementation challenge	Country/region facing implementation challenge	Type of vaccine switches (Type of vaccine)	Description of implementation challenge	Resource and costs caused by implementation challenge
1. Vaccine availability
1.1 Vaccine supply
Ensuring sufficient production scale-up	Eastern Mediterranean Region27 Sri Lanka28 Global30,31,33,39 Western Pacific Region32 India37,38 Region of Americas42,55 Pakistan43 European Region54	Switch of route of administration (Polio; from OPV to IPV)27–28-30–39-42–43-54–55	Global shortage of vaccine leading to global disparities in vaccine access27–30–39–42–54 Some countries need to use an alternative method of fractional dose of IPV instead of using full-dose IPV28,43,55	Opportunity costs of increased risk of infection to children due to missed vaccination27
1.2 Vaccine logistics
Ensuring the availability of new vaccines at the point of use	South-East Asia Region25 Argentina26 Peru50 Region of Americas55	Switch of serotype coverage (Polio; tOPV to bOPV,25,26,55 and PCV; PCV10 to PCV13)50 Switch of vaccination schedule (PCV, from 3, 5, and 12 months to 2, 4, and 12)50	Deviation from immunization protocol*	Human resources for monitoring26 Opportunity costs of increased risk of infection to children due to missed vaccination*
Ensuring sufficient cold chain requirements and storage management	Global41 Gambia53	Switch from multiple vaccinations to a combination vaccine (Pentavalent vaccine) together with introduction of PCV1353 Switch of route of administration (Polio; OPV to IPV)41 Switch of serotype coverage (Polio; tOPV to bOPV)41	Decrease in vaccine availability due to insufficient supply chain capacity* Requirement of additional shipment to deliver sufficient vaccines to the points of use*	Incremental cost for transportation in 6 health administrative regions of $US 7,251 (for the switch to combination vaccine)53 Additional cold chain investment (for both Pentavalent vaccine and PCV13) of $US 373,00053 Annualized cost of cold storage allocated to the switch to pentavalent vaccine of $US 5,18753
2. Vaccination program deployment
2.1 Training of healthcare professionals
Training and Supervision of Healthcare Professionals	Argentina26 Eastern Mediterranean Region27 Sri Lanka28 Global3,34 Benin47 Pakistan43 Burkina Faso49 Peru50 Region of Americas55 European Region56	Switch of route of administration (Polio; OPV to IPV,3,27,55,56 IM to ID)28,43 Switch of serotype coverage (Polio, tOPV to bOPV)3,26,27,34,54,55 Switch of number of doses per vial (PCV; single-dose vial to multi-dose vial)47 Switch of vaccination schedule (PCV, 3+0 to 2+1,49 and 3,5, and 12 months to 2, 4, and 12 months)50	Unintentional use of pre-switched vaccine*34 Deviation from immunization protocol47,50 Complex protocols for handling and preparing vaccines	Human resources for training and monitoring28,43,49 Time for training28,43 Resources for training material47 Opportunity costs of increased risk of infection to children due to missed vaccination50
2.2 Infrastructure and resources
Monitoring the effectiveness and safety of vaccine deployment	Eastern Mediterranean Region27 South-East Asia Region29 Sri Lanka28 Global3,35,40,44 Burkina Faso49 African Region46 Region of Americas42,55 Benin47 European Region56	Switch of route of administration (Polio; OPV to IPV)27,40,55,56 Switch of serotype coverage (Polio; tOPV to bOPV,27,29,44,46,54,55 and PCV; switch of all PCV serotypes)35 Switch of vaccination schedule (PCV; 3+0 to 2+1)49	Risk of endemic due to using the withdrawn vaccines Defining appropriate outcomes and measurements	Human resources for monitoring* System for monitoring*
Ensuring sufficient human resources	Argentina26	Switch of serotype coverage (Polio; tOPV to bOPV)26 Switch of route of administration (Polio; OPV to IPV)26	Inefficient vaccination program deployment*	Human resources for training* Time for training* Resources for training material*
2.3 Management of pre-switched vaccines
Ensuring withdrawal of pre-switched vaccines	South-East Asia Region25 Argentina26 Global3	Switch of serotype coverage (Polio; tOPV to bOPV)3,25,26	Risk of inadvertently using of pre-switched vaccine*	Human resources for monitoring25
3. Vaccine acceptability
3.1 Parental acceptability
Concern about the switch among parents and communication with parents about the switch	The US48 Global36,39,45,54 Burkina Faso49 Indonesia51 European Region56	Switch of serotype coverage (Polio; tOPV to bOPV)36,56 Switch of route of administration and additional injection of DTaP (Polio; OPV to IPV)48 Switch of route of administration (Polio; OPV to IPV)39,51,56 Switch of types of vaccines (Pertussis; whole cell to acellular)45 Switch of vaccination schedule (PCV; 3, 5, and 12 months to 2, 4, and 12 months)49 Switch to a more reactogenic strain (BCG)54	Reluctance among parents51 Vaccine hesitancy	Opportunity costs of increased risk of infection to children due to missed vaccination Human resources for communication with parents39,49
Healthcare professional acceptability
Healthcare professional reluctance in providing new vaccines to children	The US52 Yogyakarta, Indonesia51 Global54	Switch from multiple vaccinations to a combination vaccine (Pentavalent vaccine)52 Switch of route of administration (Polio; OPV to IPV)51 Switch to a more reactogenic strain (BCG)54	Reluctance in using new vaccines51,52	Opportunity costs of increased risk of infection to children due to missed vaccination and/or deviation from immunization protocol*

*Implicit impact of the challenges of vaccine switch based on the included articles and authors’ speculation. Abbreviations: 2+1; 2 primary doses with a booster dose; 3+0; 3 primary doses without a booster dose; BCG, Bacillus Calmette-Guérin; bOPV, Bivalent Oral Poliovirus vaccine; DTaP, Diphtheria-Tetanus-Pertussis; ID, Intradermal; IM, Intramuscular; IPV, Inactivated Poliovirus vaccine; OPV, Oral Poliovirus vaccine; PCV, Pneumococcal Conjugate vaccine; tOPV, Trivalent Oral Poliovirus vaccine.