VACCINE RESOURCE COMMITTEE

of the Edmonton Zone Medical Staff Association

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Diphtheria, Tetanus and Pertussis Vaccine Question #2:

Why are diphtheria, tetanus and pertussis dangerous?

DIPHTHERIA can lead to difficulty breathing, heart failure, paralysis, or death.

TETANUS causes painful stiffening of the muscles. Tetanus can lead to serious health problems, including being unable to open the mouth, having trouble swallowing and breathing, or death.

PERTUSSIS, also known as “whooping cough,” can cause uncontrollable, violent coughing that makes it hard to breathe, eat, or drink. Pertussis can be extremely serious especially in babies and young children, causing pneumonia, convulsions, brain damage, or death.  In teens and adults, it can cause weight loss, loss of bladder control, passing out, and rib fractures from severe coughing.

Diphtheria

Diphtheria is a disease caused by a bacterium that affects mucous membranes, primarily those of the upper respiratory tract and the skin. The bacterium is most commonly spread through person-to-person contact. Diphtheria became nationally notifiable in 1924. That year 9,057 cases were reported, the highest annual number of cases ever recorded in Canada. Since the inception of immunization programs in the 1930's, diphtheria is rare in Canada. However; it occurs worldwide and is still endemic in many countries.

A small number of toxigenic strains of diphtheria bacilli continue to be detected each year, although classic diphtheria is rare. Since 1993, a total of 19 cases have been reported with a range of 0 to 4 cases annually. In this time:

  • approximately 26% of cases were between the ages of 0 to 14 years

  • 74% of cases were over 25 years of age

The last death due to diphtheria in Canada was reported in 2010.

Respiratory diphtheria affects the mucous membrane of the upper respiratory tract. Symptoms include a mild fever, sore throat, difficulty swallowing, malaise and loss of appetite. Sites of infection can include the anterior nose, pharynx/tonsils or the larynx. The most common manifestation that leads to systemic infection is pharyngeal/tonsillar diphtheria. It can progress to acute respiratory distress, upper airway obstruction and asphyxia in young children. An adherent, asymmetrical, greyish-white membrane is visible on the tonsils and oropharynx typically within 2 to 3 days of illness.

Patients with severe disease may develop notable swelling in the neck area giving the characteristic bull neck appearance. Systemic complications such as myocarditis and central nervous system effects (such as muscle paralysis) can occur. This happens if the toxin produced at the site of infection is absorbed into the bloodstream. The case-fatality rate is about 5% to 10%.

Annual number of reported cases of diphtheria, Canada, 1924-2012

Source: Government of Canada: Diphtheria: For Health Professionals

Tetanus

Tetanus (also known as lockjaw) is an infection spread by a bacterium. Tetanus is rare in Canada. During the 1920s and 1930s, between 26 and 55 deaths due to tetanus were reported annually. With the introduction of tetanus toxoid in Canada in 1940, morbidity and mortality rapidly declined (see Figure 1). Between 2000 and 2013 a total of 42 cases were reported, with an average of 3 cases reported per year (range 1 to 8 cases). During this period, persons 60 years of age or greater accounted for 55% of the cases. No cases were reported among neonates. The immunization status of most of the reported cases was not known. Only six deaths have been reported in Canada since 2000, with the last death reported in 2010.

Bacteria can get in any cuts. The infection affects the nerves that control muscles. They become stiff and painful, and make swallowing and breathing difficult. Other symptoms include:

  • headache,

  • seizures (violent jerking or shaking of the body),

  • fever and sweating,

  • high blood pressure, and

  • fast heart rate.

Without proper hospital treatment, tetanus can be fatal.

Annual number of reported cases of diphtheria, Canada, 1924-2012

Source: Government of Canada: Tetanus: Health Professionals

Pertussis

Pertussis is a cyclical disease, which peaks at two to five year intervals. With the introduction of whole cell pertussis vaccine in 1943, the incidence of pertussis decreased significantly, from an average of 156 cases per 100,000 population in the five years prior to vaccine introduction, to a low of 5 cases per 100,000 (2005 to 2011).

A resurgence of pertussis was observed beginning in 1990, likely due to a combination of factors including:

  • low effectiveness of the combined diphtheria-tetanus-whole cell pertussis vaccine used in children between 1980 and 1997;

  • waning immunity among adolescents and adults;

  • increased physician awareness; and

  • improved diagnosis and reporting of pertussis infection.

The whole cell pertussis vaccines were replaced with acellular pertussis vaccines in 1997/1998, which was followed by a steady decline incidence to 2.0 cases per 100,000 in 2011.

A seven-fold increase in national incidence to 13.9 per 100,000 was observed in 2012, due to outbreaks in multiple jurisdictions across the country.

The incidence of pertussis is highest in infants and children, and decreases significantly in those older than 14 years.

The highest mean incidence rates from 2005 to 2011 were:

  • 72.2 cases per 100,000 population among infants less than 1 year of age (mean: 261 cases per year),

  • 25.6 cases per 100,000 population among 1 to 4 year olds (mean: 362 cases per year), and

  • 16.0 cases per 100,000 population among 10 to 14 year olds (mean: 328 cases per year).

Following the introduction of a single adolescent dose of acellular pertussis vaccine in 2004, between 2005 and 2011, the incidence of pertussis decreased in all age groups, most notably among those aged 10 to14 years (84% decrease) and those aged 15 to 19 years of age (81% decrease).

During the 2012 outbreak, increases in incidence were observed across all age groups nationally, with the highest incidence rates in those less than one year (120.8 per 100,000; n=460) and those 10-14 years of age (64.1 per 100,000; n=1203).

In 2024, Ontario had an outbreak. Between January 1 and November 30, 2024 there were 1,634 cases. The year-to-date 2024 incidence rate was 10.2 cases per 100,000 population. The majority of cases were among children with the highest rates in under one year and between 10-14 year olds.  

Hospitalization and death are more common among infants, particularly those 3 months of age or less. One to four deaths related to pertussis occur each year in Canada, typically in infants who are too young to be immunized, or children who are unimmunized or only partially immunized.

The clinical course of pertussis is divided into three stages. The initial catarrhal stage is characterized by runny nose, sneezing, low-grade fever, and a mild cough, similar to a cold. After 1 to 2 weeks of gradually worsening cough, the paroxysmal stage begins.

The paroxysmal stage is characterized by bursts of rapid coughing, ending with an inspiratory whoop and sometimes post-tussive vomiting. This stage can last from 2 to 8 weeks. In the convalescent stage, recovery is gradual and may take weeks to months.

The clinical course varies with age. In young infants, who are at the highest risk, clinical symptoms are frequently atypical. Whoop and post-tussive vomiting may be absent. The presentation may be characterized solely by episodes of apnea. Serious complications occur mainly in infants and may include pneumonia, atelectasis, seizures, encephalopathy, hernias and death.

Reported cases and incidence rate (per 100,0000 population) or pertussis in Canada by year, 1924 to 2012