WHO Immunization Forecasting

Cicada supports WHO Expanded Programme on Immunization (EPI) recommendations alongside the CDC's CDSi schedule. This enables immunization forecasting for global health contexts where the U.S. schedule is not applicable.

WHO Antigens

Cicada includes definitions for 22 WHO antigens:

Core EPI Antigens (12)

Antigen	Vaccine	Schedule	CVX
Tuberculosis (BCG)	BCG	Birth dose	19
Hepatitis B	HepB	Birth + 6/10/14 weeks	43, 198
Diphtheria	DTP	6/10/14 weeks + boosters	198, 01, 107
Tetanus	TT/Td	6/10/14 weeks + boosters	198, 01, 09, 139
Pertussis	DTP	6/10/14 weeks + booster at 12-23mo (3p+1)	198, 01, 107
Hib	Hib	6/10/14 weeks	198, 49, 48
Polio	OPV + IPV	6/10/14 weeks OPV + IPV at 9 months	178, 10, 89
Measles	MR/MMR	9 months + 15-18 months	04, 03
Rubella	MR/MMR	9 months + 15-18 months	04, 06
PCV	PCV	6/10/14 weeks	152, 133
Rotavirus	RV1/RV5	6/10 weeks (2-dose) or 6/10/14 weeks (3-dose)	116, 119
HPV	HPV	9-14 years (1 dose); 15+ years (2 doses); immunocompromised (3 doses)	165, 137, 62

Context-Dependent Antigens (10)

Antigen	When Recommended
Hepatitis A	Intermediate/high endemicity (1-dose) or low endemicity (2-dose)
Yellow Fever	Endemic/at-risk areas
Japanese Encephalitis	Endemic areas in Asia-Pacific
Meningococcal	Meningitis belt, outbreaks, travel
Typhoid	Endemic areas
Cholera	1-dose emergency + 2-dose endemic
Rabies	High-risk areas, post-exposure
Mumps	Where programmatically feasible
Influenza	6 WHO priority groups (healthcare workers, elderly, pregnant, chronic conditions, young children, older adults)
COVID-19	Healthcare workers, older adults 60+, immunocompromised

Key Differences from CDC

Vaccine Formulations

The WHO schedule uses different vaccine combinations than the U.S. schedule:

Pentavalent (CVX 198): DTP-HepB-Hib — a single vaccine covering 5 antigens, standard in the WHO EPI schedule but not used in the U.S.
OPV (CVX 178): Oral Polio Vaccine — WHO uses a mixed OPV+IPV schedule; the U.S. uses IPV only
MR (CVX 04): Measles-Rubella — WHO recommends MR; the U.S. uses MMR (which adds Mumps)
DTP (CVX 01): Whole-cell pertussis — WHO uses DTP (wP); the U.S. uses DTaP (aP)

Timing

WHO doses are typically scheduled at 6, 10, and 14 weeks with boosters at 12-23 months and 4-7 years. The U.S. schedule uses 2, 4, and 6 months with later boosters.

HPV

The WHO adopted a single-dose HPV schedule in 2022 for girls aged 9-14. Girls 15+ receive 2 doses. This differs from the U.S. 2-dose schedule for ages 9-14 and 3-dose for 15+.

Multi-Antigen Groups

WHO Group	Antigens
DTP	Diphtheria, Tetanus, Pertussis
MR	Measles, Rubella
MMR	Measles, Mumps, Rubella

The CDC groups are DTaP/Tdap/Td (Diphtheria, Tetanus, Pertussis) and MMR (Measles, Mumps, Rubella).

Usage

Switch to WHO Mode

import 'package:cicada/cicada.dart';

// Option 1: Pass mode to forecast function
final result = forecastFromParameters(input, mode: ForecastMode.who);

// Option 2: Set mode globally
setForecastMode(ForecastMode.who);
final result = forecastFromParameters(input);

Check Active Mode

print(currentForecastMode); // ForecastMode.who

// Access the active data directly
final antigens = activeAntigenMap; // WHO antigen definitions
final schedule = activeScheduleData; // WHO schedule data
final groups = activeMultiAntigenGroups; // WHO multi-antigen groups

Build WHO-Specific Input

The input format is the same FHIR Parameters resource. Use CVX codes appropriate for WHO vaccines:

final input = Parameters(parameter: [
  ParametersParameter(name: FhirString('2024-06-15')),
  ParametersParameter(
    name: FhirString('patient'),
    resource: Patient(
      birthDate: FhirDate('2024-01-15'),
      gender: PatientGender.female,
    ),
  ),
  // Pentavalent (DTP-HepB-Hib) at 6 weeks
  ParametersParameter(
    name: FhirString('immunization'),
    resource: Immunization(
      status: ImmunizationStatus.completed,
      vaccineCode: CodeableConcept(coding: [
        Coding(
          system: FhirUri('http://hl7.org/fhir/sid/cvx'),
          code: FhirCode('198'), // DTP-HepB-Hib (pentavalent)
        ),
      ]),
      occurrenceDateTime: FhirDateTime('2024-02-26'),
      patient: Reference(reference: FhirString('Patient/1')),
    ),
  ),
  // OPV at 6 weeks
  ParametersParameter(
    name: FhirString('immunization'),
    resource: Immunization(
      status: ImmunizationStatus.completed,
      vaccineCode: CodeableConcept(coding: [
        Coding(
          system: FhirUri('http://hl7.org/fhir/sid/cvx'),
          code: FhirCode('178'), // OPV, bivalent
        ),
      ]),
      occurrenceDateTime: FhirDateTime('2024-02-26'),
      patient: Reference(reference: FhirString('Patient/1')),
    ),
  ),
]);

final result = forecastFromParameters(input, mode: ForecastMode.who);

WHO Schedule Data

Observations

WHO-specific observation codes start at 1010+ to avoid collision with CDSi codes (001-280). There are 17 codes across two ranges:

Code	Title
1010	Lives in meningitis belt
1011	Lives in JE endemic area
1012	Lives in or traveling to YF endemic area
1013	Lives in cholera endemic/outbreak area
1014	Lives in typhoid endemic area
1015	High risk of rabies exposure
1020	Healthcare worker
1021	Older adult 60+ years
1022	Immunocompromised individual
1023	Pregnant
1024	Chronic medical condition
1025	WHO influenza priority — young child (6mo-5y)
1026	WHO influenza priority — older adult (65+)
1027	Lives in HepA intermediate/high endemicity area
1070	Serologic evidence of HepB immunity
1071	Laboratory evidence of Measles immunity

CVX-to-Antigen Mapping

The WHO schedule maps 55+ CVX codes to antigens, including WHO-specific combinations like pentavalent (CVX 198 maps to Diphtheria, Tetanus, Pertussis, HepB, and Hib).

Live Virus Conflicts

14 live virus conflict entries covering BCG, OPV, MMR, MR, Rotavirus, Yellow Fever, Measles, Rubella, Mumps, and Varicella.

ImmDS Server

Cicada's HTTP server exposes both CDC and WHO endpoints:

# Start the server
dart run bin/server.dart -p 8080

# CDC forecast (default)
curl -X POST http://localhost:8080/\$immds-forecast \
  -H 'Content-Type: application/fhir+json' \
  -d @input.json

# WHO forecast
curl -X POST http://localhost:8080/\$immds-forecast-who \
  -H 'Content-Type: application/fhir+json' \
  -d @input.json

Both endpoints accept identical FHIR Parameters input and return the same output format. The only difference is which schedule is used for evaluation and forecasting.

Generator

WHO supporting data is generated from Excel source files (the source of truth):

# Generate WHO supporting data from Excel → JSON → Dart
dart cicada_generator/lib/main.dart --who

The generated files are written to cicada/lib/generated_files/who/ and include:

22 antigen .dart files (one per antigen)
who_schedule_supporting_data.dart (schedule data)
who_antigen_supporting_data.dart (barrel file with map and list)
who_generated_supporting_data.dart (top-level barrel export)

Source data: 22 .xlsx antigen files in cicada_generator/lib/WHO/antigen/ and 5 .xlsx schedule files in cicada_generator/lib/WHO/schedule/.

WHO Antigens​

Core EPI Antigens (12)​

Context-Dependent Antigens (10)​

Key Differences from CDC​

Vaccine Formulations​

Timing​

HPV​

Multi-Antigen Groups​

Usage​

Switch to WHO Mode​

Check Active Mode​

Build WHO-Specific Input​

WHO Schedule Data​

Observations​

CVX-to-Antigen Mapping​

Live Virus Conflicts​

ImmDS Server​

Generator​