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Disease Risk - Tetanus PDF Print E-mail

 

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

Tetanus is an infectious disease caused by contamination of wounds from bacteria that live in the soil. Tetanus spores are found throughout the environment, usually in soil, dust, and animal waste. Tetanus is acquired through contact with environment; it is not transmitted from person to person. Tetanus results in severe, uncontrollable muscle spasms. In severe cases, the muscles used to breathe can spasm, causing a lack of oxygen to the brain and other organs that may possibly lead to death. Neonatal tetanus is similar to generalized tetanus except that it affects a baby that is less than 1 month old [1].  Tetanus is almost fully preventable with proper injury treatment.

Although tetanus still is a very serious disease, the prognosis with modern techniques of intensive care is markedly better than that predicted by earlier statistics.  With appropriate intensive care, the ultimate mortality rate of tetanus in the United States has been reduced greatly. The overall case-fatality rate in the United States has declined from 91% in 1947, to 24% during 1989 to 1991, to 11% during 1995 to 1997.  No mortality was observed in the United States between 1995 and 1997 in individuals younger than 25 years of age. Survivors are left largely without sequelae of tetanus [2].  Among all ages during 1998-2000, 130 cases were reported with 20 deaths; all reported deaths occurred among patients aged 33-88, with 75% (15/20) of the deaths in patients aged 60 and older [3].

Case Fatality Rate: Age plays an important part in outcome, with only 5% mortality rate for patients younger than 50 years of age, as compared to 42% for those older than 50. For the purposes of this analysis, we use the 5% case mortality rate in tetanus cases due to acute injury [2].

Rate of Long Term Sequelae or Injury: Tetanus due to acute injury or wounds can be appropriately managed medically with antibiotics to kill the bacteria, tetanus booster shot if necessary, and occasionally antitoxin to neutralize the toxin [1]; survivors are left largely without sequelae of tetanus [2].  For the purposes of this analysis, we use a 0% case sequelae rate in tetanus cases due to acute injury.

Incidence Rates:  In the United States, the average annual incidence of tetanus during 1998--2000 was 0.05 cases per million population among persons aged <20 years [3].  In 1947 through 1949, before widespread use of the vaccine, an average of 580 cases of tetanus and an average of 472 deaths from tetanus were reported [5].  During 1972--2006, the cumulative number of reported neonatal tetanus cases decreased to 32; the most recent cases were reported in 1989, 1995, 1998, and 2001.[4]

Incremental Risk in Population with Low Rates of Vaccination (if a child does not vaccinate by age 5):

Tetanus is not contagious from person to person [1].  Instead, the risk to a child under age 5 consists of a) the risk of neonatal tetanus and b) risk of tetanus from acute injury.

Since a child is not vaccinated for tetanus until ages 2, 4, and 6 months, the vaccination status of the child does not affect the risk of neonatal tetanus so the incremental risk of neonatal tetanus from the child not vaccinating is zero.

The risk to a child from tetanus due to acute injury is based upon the risk of an acute injury and whether the child is vaccinated.  To determine the average risk of an unvaccinated child contracting tetanus from an acute injury, we utilized the reported tetanus cases in the pre-vaccine era (1947 – 1949) of 580 cases per year [5] and assumed 75% of cases were reported to calculate an estimated tetanus incidence rate per year amongst unvaccinated individuals in the USA of 0.05 per 10,000 or 1 in 190,000.  The cumulative risk of death from tetanus due to acute injury up to age 5 was calculated to be 0.013 per 10,000 or 1 in 759,000.  The cumulative risk of permanent injury from tetanus due to acute injury was calculated to be 0.00 per 10,000, since those who survive do not generally have permanent sequelae [2].  Since tetanus is rare amongst vaccinated individuals, all of this calculated risk is considered to be incremental risk incurred due to the hypothetical decision that a child does not vaccinate until age 5.

Incremental Risk in Highly Vaccinated Population (if a child does not vaccinate by age 5): Tetanus is not transmitted from person to person.  Therefore, the risks to a child who does not vaccinate by age 5 are the same when children in the population are highly vaccinated as the risks when children in the population have low rates of vaccination (see analysis above).

Note: This analysis analyzes the risks based upon a hypothetical decision for a child to not vaccinate until age 5.  Although there is an increased risk to that hypothetical child of neonatal tetanus if the mother is not fully vaccinated for tetanus, the decision of the mother to vaccinate prior or during child-bearing years was deemed not in scope for this analysis.

 

References:

[1] Tetanus article on eMedicineHealth: http://www.emedicinehealth.com/tetanus/article_em.htm

[2] Oski’s Pediatrics: Principles & Practice.  By Julia A. McMillan, Ralph D. Feigin, Catherine DeAngelis, M. Douglas Jones.  2006. page 1033.

[3] Centers for Disease Control and Prevention:  Tetanus Surveillance – United States, 1998-2000.  MMWR, Surveillance Summaries, June 20, 2003 / 52 (S S03);1-8

[4] Centers for Disease Control and Prevention:  Prevention of Pertussis, Tetanus, and Diphtheria Among Pregnant and Postpartum Women and Their Infants. MMWR, Recommendations and Reports, May 30, 2008 / 57 (04);1-47, 51

[5] http://www.cdc.gov/vaccines/vpd-vac/tetanus/downloads/dis-tetanus-bw-office.pdf

[6] Okoromah CAN, Lesi FEA .  Diazepam for treating tetanus. 2004. http://www.nichd.nih.gov/cochrane/okoromah/okoromah.htm#Background

[7] P Teknetzi, S Manios, and V Katsouyanopoulos. Neonatal tetanus---long-term residual handicaps. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1628125/pdf/archdisch00750-0076.pdf

[8] http://www.census.gov/popest/archives/1990s/popclockest.txt