Methods

VaxImpactMap uses simple analytical epidemiological models calibrated to current state-level vaccination coverage, birth rates, and disease surveillance data. The models are based on the idea that declines in coverage will only affect new births. Older children who were vaccinated as babies retain the immunity conferred by immunization.  Therefore, gaps in immunity take time to accrue. 

Disease parameters (transmission rates, severity, case-fatality ratios) are derived from CDC surveillance, published literature, and historical outbreak data. Economic costs include direct medical expenses and indirect productivity losses, calculated using standard health economics methods.

For detailed technical documentation, including model equations, parameter values, and validation procedures, see:
VaxImpactMap Technical Methods

Data Sources

Descriptions, values, and references for model parameters are listed below. All natural history parameters were fixed at values informed by the literature. 

Parameter

Rotavirus

Pertussis

Pneumococcal

Notes

Model structure

SIR2

SIRS2,4

SIRS5,6

 

Modeled age band

0-4 years

0-14 years

0-4 years

 

Basic reproduction number

 4†

5†

5†

†We started with R0 values from the literature then calibrated values so as to match disease burden and impact of vaccination in the modeled age bands observed is the US population.

Vaccine effectiveness

0.9157

0.8508,9

0.90210

 

Vaccination coverage

State-specific11

State-specific12

State-specific11

 

Waning immunity rate***

none

0.18

0.113

***Waning immunity rate is expressed per year and assumes exponential loss of protection.

Demographic turnover rate

1/R**

1/R**

1/R**

** R denotes age-band width (years), such that the demographic turnover (µ) = 1/R.

Hospitalization rate

0.0143‡

0.05‡

0.83‡

‡Hospitalization and death rates are estimated proportions conditional on cases.

Death rate

0.0000074‡

0.0005‡

0.0369‡

 

Average illness duration

5 days14

14 days14

8 days

 

Average hospitalization duration

5 days14

5.3 days15

4 days16

 

Average daily hospitalization cost

$1,74817

$1,66518

$4,75819, 16

 

Average daily wage

$ 20020,21

$ 20020,21

$ 20020,21

 

Observed national cases

Derived

20,96022

Derived

 

Observed national hospitalizations

7,500∆

1,027∆

1,38223,3

∆Observed national hospitalizations were used directly when available; otherwise, national case targets were inferred by back-calculating from hospitalization counts using disease-specific hospitalization probabilities.

Observed national deaths

5§

1022

5123

§Observed national death are estimated national death targets.

National case targets were derived from hospitalization targets using disease-specific hospitalization rates when direct cases estimates were unavailable. For pneumococcal disease, hospitalization and death rates are conditional on invasive pneumococcal infection. National hospitalization and death targets reflect observed annual IPD burden among children aged <5 years.

Calibration was performed at the case level only; costs were derived from calibrated outcomes.

Vaccine effectiveness (VE) is assumed to be against infection – for each pathogen, a proportion of infections become cases, and cases become hospitalized or die. VE is the direct protection against infection. Non linear effects (like herd immunity) are captured by the incidence equation. 

 

References

  1. Keeling MJ. Modeling Infectious Diseases in Humans and Animals. Princeton University Press; 2008.
  2. Hethcote HW. The Mathematics of Infectious Diseases *. Vol 42. 2000:599-653. http://www.siam.org/journals/sirev/42-4/37190.html
  3. CDC. ABCs Bact Facts Interactive Data Dashboard. Active Bacterial Core surveillance (ABCs). August 21, 2025. Accessed January 27, 2026. https://www.cdc.gov/abcs/bact-facts/data-dashboard.html
  4. Roddam AW. Mathematical Epidemiology of Infectious Diseases: Model Building, Analysis and Interpretation: O Diekmann and JAP Heesterbeek, 2000, Chichester: John Wiley pp. 303, £39.95. ISBN 0-471-49241-8. Int J Epidemiol. 2001;30(1):186-186. doi:10.1093/IJE/30.1.186
  5. Malik TM, Mohammed-Awel J, Gumel AB, Elbasha EH. Mathematical assessment of the impact of cohort vaccination on pneumococcal carriage and serotype replacement. J Biol Dyn. 2021;15(S1):S214-S247. doi:10.1080/17513758.2021.1884760
  6. Løchen A, Anderson RM. Corrigendum to “Dynamic transmission models and economic evaluations of pneumococcal conjugate vaccines: a quality appraisal and limitations” [Clin Microbiol and Infect 26 (1) (2020) 60–70]. Clin Microbiol Infect. 2021;27(10):1545-1545. doi:10.1016/j.cmi.2021.07.001
  7. Martinón-Torres F, Bouzón Alejandro M, Redondo Collazo L, et al. Effectiveness of rotavirus vaccination in Spain. Hum Vaccin. 2011;7(7):757-761. doi:10.4161/hv.7.7.15576
  8. Domenech De Cellès M, Rohani P, King AA. Duration of Immunity and Effectiveness of Diphtheria-Tetanus-Acellular Pertussis Vaccines in Children. JAMA Pediatr. 2019;173(6):588-594. doi:10.1001/jamapediatrics.2019.0711
  9. Redfield RR, Kent CK, Leahy MA, et al. Prevention of Pertussis, Tetanus, and Diphtheria with Vaccines in the United States: Recommendations of the Advisory Committee on Immunization Practices (ACIP) Morbidity and Mortality Weekly Report Recommendations and Reports Centers for Disease Control and Prevention MMWR Editorial and Production Staff (Serials) MMWR Editorial Board. Vol 67. 2018. https://www.cdc.gov/vaccines/acip.
  10. Andrejko KL, Gierke R, Rowlands JV, et al. Effectiveness of 13-valent pneumococcal conjugate vaccine for prevention of invasive pneumococcal disease among children in the United States between 2010 and 2019: An indirect cohort study. Vaccine. 2024;42(16):3555-3563. doi:10.1016/j.vaccine.2024.04.061
  11. Vaccination Coverage among Young Children (0 – 35 Months) | ChildVaxView | CDC. https://www.cdc.gov/childvaxview/about/interactive-reports.html
  12. Vaccination Coverage and Exemptions among Kindergartners | SchoolVaxView | CDC. https://www.cdc.gov/schoolvaxview/data/index.html#cdc_data_surveillance_section_1-schoolvaxview-interactive
  13. Nurhonen M, Cheng AC, Auranen K. Pneumococcal Transmission and Disease In Silico: A Microsimulation Model of the Indirect Effects of Vaccination. PLoS ONE. 2013;8(2). doi:10.1371/journal.pone.0056079
  14. Table of Contents | Pink Book | CDC. https://www.cdc.gov/pinkbook/hcp/table-of-contents/index.html
  15. Lopez MA, Cruz AT, Kowalkowski MA, Raphael JL. Trends in hospitalizations and resource utilization for pediatric pertussis. Hosp Pediatr. 2014;4(5):269-275. doi:10.1542/hpeds.2013-0093
  16. Mohanty S, Cossrow N, White M, et al. Burden of invasive pneumococcal disease, non-invasive all-cause pneumonia, and acute otitis media in hospitalized US children: a retrospective multi-center study from 2015 to 2020. BMC Health Serv Res. 2024;24(1). doi:10.1186/s12913-024-11898-w
  17. Widdowson MA, Meltzer MI, Zhang X, Bresee JS, Parashar UD, Glass RI. Cost-effectiveness and potential impact of rotavirus vaccination in the United States. Pediatrics. 2007;119(4):684-697. doi:10.1542/peds.2006-2876
  18. Masseria C, Martin CK, Krishnarajah G, Becker LK, Buikema A, Tan TQ. Incidence and burden of pertussis among infants less than 1 year of age. Pediatr Infect Dis J. 2017;36(3):e54-e61. doi:10.1097/INF.0000000000001440
  19. Averin A, Weycker D, Lapidot R, et al. Cost of invasive pneumococcal disease, all-cause pneumonia, and all-cause otitis media among commercial-insured US children. J Med Econ. 2025;28(1):517-523. doi:10.1080/13696998.2025.2484919
  20. USUAL WEEKLY EARNINGS OF WAGE AND SALARY WORKERS FIRST QUARTER 2025. www.bls.gov/cps
  21. Total private average hourly earnings and weekly hours and earnings by state. https://www.bls.gov/charts/state-employment-and-unemployment/average-hourly-earnings-and-weekly-hours-and-earnings-by-state.htm
  22. CDC, Ncird. 2024 Provisional Pertussis Surveillance Report – January 2025. 2024. https://wonder.cdc.gov/nndss/static/2024/52/2024-52-table990.html
  23. Wasserman M, Chapman R, Lapidot R, et al. Twenty-year public health impact of 7- And 13-valent pneumococcal conjugate vaccines in US children. Emerg Infect Dis. 2021;27(6):1627-1636. doi:10.3201/eid2706.204238