Immunization is one of the most important advances in public health and is estimated to have saved more lives in Canada over the past 50 years than any other health intervention. Before vaccines became available, many Canadian children died from diseases such as diphtheria, measles and polio that are now preventable by immunization. Immunization programs are responsible for the elimination, containment or control of infectious diseases that were once common in Canada; however, the viruses and bacteria that cause vaccine preventable diseases still exist globally, can be imported to Canada through travel, and can be transmitted to people who are not protected by immunization. If immunization programs were reduced or stopped, diseases that are now rarely seen in Canada because they are controlled through immunization would re-appear, resulting in epidemics of diseases causing sickness and death. This phenomenon has been seen in other countries; for example, large epidemics of diphtheria and measles have occurred in Europe in recent decades after immunization rates declined.
Immunization is important in all stages of life. Infants and young children are particularly susceptible to vaccine preventable diseases because their immune systems are not mature enough to fight infection; as a result, they require timely immunization. Older children and adults also require immunization to restore waning immunity and to build new immunity against diseases that are more common in adults.
Immunization directly protects individuals who receive vaccines. Through herd immunity, immunization against many diseases also prevents the spread of infection in the community and indirectly protects:
Table 1, Figures 1, 2, and 3 illustrate the impact of vaccines on infectious diseases in Canada. Refer to Part 4 chapters for additional information about the success of immunization programs against specific vaccine preventable diseases.
|Disease and impact||Vaccine introduction & Disease reporting||Pre-vaccine era||2007-2011Footnote 1|
|Pre-vaccine period||5-year average annual incidence per 100,000||Peak annual number of casesFootnote *||5-year average annual incidence per 100,000||Peak annual number of cases|
Infection of the throat causes severe breathing difficulty which may result in asphyxia. Infection also results in the dissemination of diphtheria toxin, which damages the heart and central nervous system. In the pre-vaccine era case fatality was about 5% to 10%, with highest death rates occurring in the very young and the elderly.
|Haemophilus influenzae type b (Hib) invasive disease (children less than 5 years of age)
Infection can cause meningitis, epiglottitis, bacteremia, cellulitis, pneumonia or septic arthritis in young children. Case fatality rate of meningitis is about 5%. Severe neurologic sequelae occur in 10% to 15% of survivors and deafness in 15% to 20%
||1986-1990||30.1Footnote 2||671||0.49Footnote 2||18|
|Hepatitis B (HB)
Infection in approximately 10% of adults results in chronic infection leading to a chronic carrier state that may result in cirrhosis, liver cancer, and death.
||1989-1993||9.1Footnote 3||3,378Footnote 4||5.3Footnote 5||2,011Footnote 6|
Bronchopneumonia and otitis media occur in about 1/10 cases and encephalitis occurs in 1/1,000 cases (fatal in 15% and neurologic sequelae in 25%). Case fatality rate is 1-2 per 1000. Subacute sclerosing panencephalitis is a rare but fatal complication.
||1950-1954||372.7||61,370||0.60Footnote 7||752Footnote 7|
|Meningococcal serogroup C invasive disease
Invasive meningococcal disease most often results in meningitis or septicemia. Severe cases can result in delirium and coma and, if untreated, shock and death. Case fatality rate is 10%, and 10-20% of survivors have severe sequelae such as limb amputations and deafness.
Acute parotitis develops in 40%, of which 25% are unilateral. Complications include orchitis (20% to 30% of post-pubertal males), oophoritis (5% of post-pubertal females), meningitis (<10% of cases), deafness (0.5 to 5/100,000 cases) and encephalitis (less than 1/50,000 cases). Occasionally mumps can cause permanent infertility or deafness.
Young infants may experience complications, such as vomiting after a coughing spell, weight loss, breathing problems, choking spells, pneumonia, convulsions, brain damage, and in rare cases, death. Older children and adults develop persistent cough lasting for up to 6 weeks.
Paralysis occurs in less than 1% of infections but among those paralyzed, about 2 - 5% of children and 15-30% of adults die.
|Rubella and congenital rubella syndrome (CRS)
Although rubella is generally a mild disease, encephalitis occurs in 1/6,000 cases. However, rubella infection in pregnancy can cause congenital rubella syndrome (CRS). Infection in the first 10 weeks of pregnancy has an 85% risk of leading to CRS. CRS can result in miscarriage, stillbirth and fetal malformations (congenital heart disease, cataracts, deafness and mental retardation).
CRS: 3.08Footnote 8
CRS: 0.11Footnote 8
Infection leads to general rigidity, and convulsive spasms, with death in about 10% of cases. Higher rates of death occur among infants.
Population data sources: Statistics Canada, Population by Sex and Age, 1921-1971, revised annual estimates of population, Canada and the provinces, (Catalogue 91-512) Statistics Canada, Population estimates 0-90+ July Canada - Provinces 1971-2008.xls
Vaccine preventable diseases result in significant costs to individuals, the health care system, and society, including costs associated with visits to health care providers, hospitalizations, and premature deaths. Parents may lose time from work to care for sick children and sick children lose time at school. For example, the societal cost for each case of rotavirus requiring a visit to the emergency room is estimated to be $675.
The cost-benefit of vaccine is strongly influenced by the price of the vaccines used. Many vaccines, such as measles-mumps-rubella vaccine for children, provide both health benefits and savings in health care costs (refer to Table 2). This means that the cost of implementing the immunization program is less than the cost of treating the illness or injury that would occur if the program had not been not implemented. Because immunization with these vaccines improves health and results in cost savings, the decision to include these vaccines in publicly funded immunization programs is straightforward. In developing public health programs, international organizations such as the World Health Organization, United Nations Children’s Fund and the World Bank recommend that immunization be given high priority because of its high cost-effectiveness.
|Immunization program||Cost saving per $1 spent|
|Influenza for adults 65 years of age and older||$45|
|Measles, mumps, rubella for children||$16|
|Pneumococcal polysaccharide for adults 65 years of age and older||$8|
|Diphtheria, pertussis, tetanus for children||$6|
Newer vaccines tend to be costlier and may not be cost-saving, so the decision to introduce them into publicly funded immunization programs is determined by society’s willingness to pay for their anticipated health benefits. In general, such programs compare very favourably to other public health interventions in terms of cost per life year saved (refer to Table 3). In Canada, evaluation of benefits and costs of new immunization programs is done by Provinces and Territories. Refer to Immunization in Canada for more information.
|Public health intervention||Cost per life year savedFootnote 1|
|Hepatitis B screening in pregnancy and immunization of children of carriers||$164|
|Human papillomavirus vaccine for 12 year old girls in a school-based immunization program||$12,921|
|Varicella vaccine for children||$16,000|
|Pneumococcal conjugate vaccine for children||$125,000|
|Mandatory seat belt law||$69|
|Chlorination of drinking water||$3,100|
|Smoking cessation counseling||$1,000 to $10,000|
|Annual screening for cervical cancer||$40,000|
|Driver and passenger air bags/manual lap belts (vs. airbag for driver only and belts)||$61,000|
|Smoke detectors in homes||$210,000|
|Crossing control arm for school buses||$410,000|
|Radiation emission standard for nuclear power plants||$100,000,000|