Disease Risk – Hepatitis A

 

Risk to a child from Hepatitis A if not vaccinated until after the age of 5:

Case Fatality Rate: Case fatality rates for Hepatitis A are generally quite low, are heavily weighted toward older adults, and vary widely with risk factors. [1][2] Previous reports have shown a case-fatality rate of only 0.01% to 0.03% [3] but an increased risk of death with age – up to 2% in adults [1].  Because the risk of death is higher in adults, for the purposes of this analysis the case fatality rate of 0.01% is used.

Complications: Although Hepatitis A can result in serious illness (with adults being at higher risk) permanent injury from Hepatitis A is rare enough that it is not generally listed.

Incremental Risk in Population with Low Rates of Vaccination (if a child does not vaccinate by age 5): Prior to the induction of the vaccine, the US average was 10 cases per 100,000 across all age groups.  The case fatality rate is the same as in the analysis for the High-vaccination population.  The estimated case fatality rate would be 0.0001.The 5-year cumulative risk of death for a child under 5 is 0.0005 per 10,000, or 1 in 20 million.

Incremental Risk in Highly Vaccinated Population (if a child does not vaccinate by age 5): Since the introduction of the vaccine, incidence rates have decreased from 10 cases per 100,000 to approximately 2.5 per 100,000 in the 2-18 year old age range [1].  If we assume that all cases are in unvaccinated population (59.6% unvaccinated [4]) the estimated case rate is 4.19 per 100,000.  Using the case fatality rate of 0.01% for ages 0-5, the case fatalities per year is estimated to be 0.00042 per 100,000 or 0.000042 per 10,000 per year. The 5-year cumulative risk of death for a child under 5 is 0.000209 per 10,000, or 1 in 48 million.

 

References:

[1] Centers for Disease Control and Prevention: Epidemiology and Prevention of Vaccine-Preventable Disease. Atkinson W, Wolfe S, Hamborsky J, McIntyre L. eds. 11th edition. Washington D.C.: Public Health Foundation, 2009.

[2] Serious Hepatitis A:  An Analysis of Patients Hospitalized during an Urban Epidemic in the United States.  Willner I, Uhl M, Howard S, Williams E, Riely C, Waters B.  Annals of internal medicine Volume 128, Number 2, 1998.

[3] Melnick JL.  History and epidemiology of hepatitis A virus.  J Infect Dis.  1995 171(Suppl 1);s2-s8

[4] CDC. National, State, and Local Area Vaccination Coverage Among Children Aged 19-35 Months—United States, 2008. MMWR 58(33);921-926.