Disease Risk – Rubella

 

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

According to the CDC [1]:

  • Rubella infection during pregnancy can lead to miscarriage, stillbirth, premature delivery, and birth defects. The danger is highest for women who get rubella during the first 12 weeks of pregnancy. Birth defects caused by rubella include deafness, cataracts, and heart defects. Babies also may have mental retardation. This group of health problems is called Congenital Rubella Syndrome (CRS) [1]
  • Rubella almost never causes serious illness or complications in infants and young children [1]
  • The prevention of Congenital Rubella Syndrome (CRS) is the main objective of the rubella vaccination programs in the United States [1]
  • The first rubella vaccines were licensed in 1969 [2]

Before licensing of the live attenuated vaccine in 1969, rubella in the United States was primarily a disease of school-aged children, with a peak incidence in children aged 5-9 years [3]. Following widespread use of rubella vaccine in children, peak incidence has shifted to persons older than 20 years, who comprise 62% of cases of rubella reported in the United States [3].

Incidence Rates:  Since rubella and congenital rubella syndrome became nationally notifiable diseases in 1966, the largest annual total of cases of rubella reported in the United States was in 1969 when 57,686 cases were reported (58 cases per 100,000 population) with 29 deaths and 31 cases of CRS [2][3].  From 2004 – 2008 an average of 12 cases of rubella were reported per year in the United States [4].  Previously the peak age group for infection was 5 -9 year olds, but since the introduction of the vaccine adults now comprise the largest group [2].

Case Fatality Rate: In 1969, the year with the largest annual total of cases since rubella became a nationally notifiable disease in 1966, there were 57,686 cases reported with 29 deaths and 31 cases of CRS [3].  For the purposes of this analysis, a case fatality rate of 29 / 57,686 or 0.0005 was used.

Rate of Long Term Sequelae or Injury: Rubella almost never causes serious illness or complications in infants and young children [1]. Infection in younger children is characterized by mild constitutional symptoms and rash [3]. Complications of rubella are not common, but they gener­ally occur more often in adults than in children [2].  Encephalitis occurs in one in 6,000 cases, more frequently in adults (especially in females) than in children [2].  Permanent sequelae from rubella is very rare, and there are no figures available [7][8][9].  For the purposes of this analysis, it is assumed that 5% of rubella encephalitis cases result in permanent injury.

Incremental Risk in Population with Low Rates of Vaccination (if a child does not vaccinate by age 5): Rubella almost never causes serious illness or complications in infants and young children, so the prevention of Congenital Rubella Syndrome (CRS) is the main objective of the rubella vaccination programs in the United States [1]. The rubella vaccine is administered after the age of 12 months, and thus confers no protection against CRS for the child being vaccinated; instead, children are vaccinated to minimize the risk of CRS to unborn children.  The vaccination status of the child does not affect the risk of CRS to that child; therefore, the incremental risk of CRS from that child choosing to not vaccinate would be zero.

The risk of death from rubella to the unvaccinated child is extremely low.  Assuming 75% of cases were reported in 1969, and assuming an equivalent risk of death and permanent injury across all age groups, the cumulative risk of death in the first five years of life to a child who does not vaccinate was calculated to be 0.0095 per 10,000 or 1 in 1,048,329.  The cumulative risk of permanent injury was calculated to be 0.00016 per 10,000 or 1 in 63,242,121.

Incremental Risk in Highly Vaccinated Population (if a child does not vaccinate by age 5): From 2004 – 2008 an average of 12 cases of rubella were reported per year in the United States [4].  No deaths or permanent injuries were reported.  The cumulative risk of death and permanent injury in the first five years of life to a child who does not vaccinate was calculated to be zero.

 

 

 

References:

[1] Centers for Disease Control and Prevention. Diseases and the Vaccines that Prevent Them: Rubella.   http://www.cdc.gov/vaccines/vpd-vac/rubella/downloads/dis-rubella-bw-office.pdf

[2] 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.  {a.k.a. “The Pink Book”}  http://www.cdc.gov/vaccines/pubs/pinkbook/downloads/rubella.pdf

[3] EMedicine. Pediatric Rubella. http://emedicine.medscape.com/article/968523-overview#a0199

[4] Center for Disease Control and Prevention.  Notifiable Diseases/Deaths in Selected Cities Weekly Information.  MMWR2009; 58(45): 1276-1287.

[5] http://www.infoplease.com/ipa/A0005067.html

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

[7] Cantwell, RJ. Rubella Encephalitis. Br Med J. 1957 December 21; 2(5059): 1471–1473. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1962912/?page=1

[8] KK Lau, ST Lai, JY Lai, WW Yan, TMK So, TY Wong. Acute Encephalitis Complicating Rubella.  HKMJ, September 1998. Vol 4, No 3. http://sunzi.lib.hku.hk/hkjo/view/22/2200435.pdf

[9] Sherman, FE, Michaels, RH, and Kenny, FM. Acute Encephalopathy (Encephalitis) Complicating Rubella. JAMA, May 24, 1965. Vol 192, No. 8. http://jama.ama-assn.org/content/192/8/675.full.pdf+html