Invasive Pneumococcal Disease

For Health Professionals

Invasive pneumococcal disease (IPD) is an acute and serious communicable disease caused by the bacterium Streptococcus pneumoniae. Invasive disease may lead to several syndromes including meningitis and bacteremia. The National Advisory Committee on Immunization (NACI) recommends immunization against pneumococcal disease.

Agent of disease

Invasive pneumococcal disease (IPD) is caused by the gram positive bacterium S. pneumoniae. There are currently 92 serotypes recognized worldwide, 15 of which cause the majority of disease. In Canada, approximately 50 different serotypes are identified each year.

Reservoir

Humans.

Spectrum of clinical illness

Transient pneumococcal colonization of the upper respiratory tract is common among healthy people; colonization is estimated to occur in 20 to 60% of healthy children. Most typically, colonized individuals are asymptomatic carriers and show no observable symptoms.

In a small proportion of carriers, the bacterium invades a normally sterile site, such as the blood or meninges, leading to invasive pneumococcal disease (IPD). Symptoms can occur as soon as 1 to 3 days after infection. Pneumonia with secondary bacteremia, bacteremia, and meningitis are the most common forms of IPD.

Bacteremia is the most common manifestation of IPD among children 2 years of age and younger. Bacteremic pneumococcal pneumonia is the most common presentation among adults and is a common complication following influenza. The case fatality rate of bacteremic pneumococcal pneumonia is 5% to 7%, and is higher among elderly persons.

Transmission

In Canada, invasive pneumococcal disease (IPD) is more common in the winter and spring. Pneumococcal disease has an incubation period that is not clearly defined, and may be as short as 1 to 3 days. S. pneumoniae can be spread by direct oral contact, respiratory droplets, or indirect contact with respiratory secretions of infected or colonized persons (e.g. sneezing, coughing or talking).

A person is capable of transmitting disease to others as long as the bacteria are present in secretions from the nose and mouth. Transmission stops when the bacteria disappear from the nose and mouth, usually within 24 hours after appropriate antimicrobial treatment has been initiated.

Disease distribution (global)

Infections caused by S. pneumoniae are a major cause of morbidity and mortality worldwide, and pneumonia is the most common cause of pneumococcal-attributed death. The World Health Organization estimates that worldwide, almost 500,000 deaths among children aged less than 5 years are caused by pneumococcal disease each year. Pneumococci are also among the top 2 causes of bacterial meningitis in infants and young children. In Europe and the United States (US), bacteremia affects approximately 15 to 19 of every 100,000 adults and meningitis affects about 1 to 2 of every 100,000 adults each year.

For more information on the global distribution of the disease, refer to the World Health Organization.

Risk Factors

Invasive pneumococcal disease (IPD) is most common in the very young, the elderly and groups at high risk. Susceptibility to infection increases as the result of conditions that affect the integrity of the lower respiratory tract, (e.g. influenza, pulmonary edema, chronic lung disease, exposure to environmental irritants such as cigarette smoke (active and passive smoking)) as well as some chronic conditions (e.g. deficient splenic function, congenital or acquired immune deficiency, cardiovascular disease).

Prevention and control

Among the 92 recognized serotypes of S. pneumoniae, invasive disease caused by 24 serotypes can be prevented by vaccination. Antimicrobial resistance among some pneumococci makes prevention through the use of vaccines even more important.

There are two main types of vaccine to prevent IPD: conjugate pneumococcal vaccines and pneumococcal polysaccharide vaccines. Conjugate vaccines are recommended for routine immunization of infants. The polysaccharide vaccine is recommended for those over the age of 2 years who are at high risk of IPD and all healthy adults. The Canadian Immunization Guide contains a summary of the serotypes contained in the vaccines available for use in Canada.

For specific recommendations about pneumococcal vaccines and their use, please refer to the most recent Canadian Immunization Guide as well as NACI statements on pneumococcal disease).

Epidemiology of Invasive Pneumococcal Disease in Canada

Invasive pneumococcal disease (IPD) has been nationally notifiable in Canada since 2000. Data is collected through the Canadian Notifiable Disease Surveillance System (CNDSS). This system does not link epidemiological and laboratory data for IPD. However, limited IPD serotype information in Canada is available through reference testing of isolates by the National Microbiology Laboratory (NML)'s Streptococcus Surveillance, beginning in 2010. This is a voluntary, passive surveillance system where isolates are submitted to the NML for diagnostic reference services. This surveillance system is not nationally representative; it is limited by reporting differences between jurisdictions, and variability in sample sizes amongst the smaller jurisdictions that result in small counts representing large relative proportions, and the availability of bacterial isolates submitted for testing.

The epidemiology of IPD has been greatly impacted by the introduction of effective vaccines. Between 2002 and 2006, the 7-valent pneumococcal conjugate vaccine (Pneu-C-7) was introduced to the routine immunization schedule across all Canadian provinces and territories. The 10-valent pneumococcal conjugate vaccine (Pneu-C-10) came on the market in 2009, and in 2010 to 2011, the 13-valent pneumococcal conjugate vaccine (Pneu-C-13) was incorporated into the routine immunization schedule for all Canadian provinces and territories, replacing the Pneu-C-7 vaccine. The 23-valent polysaccharide pneumococcal vaccine (Pneu-P-23) vaccine was licensed for use in Canada in 1983. Since 2001, all provinces and territories offer it to those aged 65 and older and for persons under 64 years with chronic medical conditions that predispose them to IPD.

According to the published literature, following the introduction of the Pneu-C-7 vaccine, a large decrease in paediatric cases of IPD, attributable to Pneu-C-7 associated serotypes, were reported. A decrease was also observed in the of incidence Pneu-C-7 serotype IPD cases among those aged 65+ years; an indirect effect of immunization in the paediatric age group. In subsequent years, however, the incidence of IPD caused by non-vaccine serotypes was noted to increase. Following the introduction of the Pneu-C-13 vaccine, preliminary data suggest that, while the overall incidence of IPD has remained relatively unchanged, declines in the paediatric population have been considerable; however data on vaccine effectiveness for Pneu-C-13 is pending.

As described in Figure 1, the number of cases of IPD reported through CNDSS has ranged from 1358 to 3326 between 2000 and 2011 in Canada. The overall incidence of IPD appears to have increased steadily from 2000 to 2004, followed by more moderate changes in incidence until reaching a plateau from 2008 to 2011. However, this is likely an artefact of IPD's recent addition (2000) to the list of nationally notifiable diseases. Importantly, serotype data is not available at the national level, limiting the ability to discern the impact of particular serotypes (preventable by vaccine, or not) on the overall incidence of IPD.

Figure 1 – Reported cases and incidence rate (per 100,000 population) of invasive pneumococcal disease (IPD) in Canada by year, 2000 to 2011Footnote * 

Text Equivalent - Figure 1

In Canada, the annual number of cases of invasive pneumococcal disease ranged from 1358 to 3326, between 2000 and 2011 (1,358 in 2000; 1733 in 2001; 2,261 in 2002; 2,725 in 2003; 2,914 in 2004; 2,857 in 2005; 2,883 in 2006; 3,240 in 2007; 3,187 in 2008; 3,288 in 2009; 3,326 in 2010; 3,277 in 2011). The number of cases appeared to increase from 2000 to 2004, but this is likely an artefact of IPD’s recent addition to the list of nationally notifiable diseases in 2000.

The annual incidence rate of invasive pneumococcal disease in Canada between 2000 and 2011 ranged from 4.4 to 9.8 cases per 100,000 population. Incidence increased from 4.4 to 9.1 cases per 100,000 population from 2000 to 2004, and was relatively stable for 2005 and 2006 at 8.9 cases per 100,000 population. From 2007 to 2011, incidence has been relatively stable, at an average value of 9.7 cases per 100,000 population (range 9.5 to 9.9).

The overall incidence of IPD ranged from 4.4 to 9.8 cases per 100,000 population during the 2000 to 2011 time period. Average age-specific incidence rates (per 100,000 population) during this time period were 34.6 among infants < 1 year of age, 22.8 among children 1 to 4 years, and 19.0 among adults = 60 years. Children < 1 year of age accounted for 4% of cases, those aged 1 to 4 years accounted for 11%, and adults = 60 years accounted for 40% of IPD cases reported in Canada.

Figure 2: Percentage of serotyped cases of invasive pneumococcal diseaseFootnote 1  by age group and associated vaccine serotype Footnote 2 in Canada, 2011.

Text Equivalent - Figure 2

This is a 100 percent stacked bar graph, showing the percentage of cases of invasive pneumococcal disease, by age group and associated vaccine serotype in Canada for 2011. The y-axis shows percentage, ranging from 0 to 100%. The x-axis indicates age group, as follows: less than 2 years, 2 to 4 years, 5 to 14 years, 15 to 49 years, 50 to 64 years, 65 years or greater, and all ages. Within each column, serotypes are grouped by their associated vaccine type. Pneu-C-7 refers to serotypes 4, 9V, 6B, 14, 18C, 19F and 23F; Pneu-C-10 to serotypes 1, 5, and 7f; Pneu-C-13 to serotypes 3, 6A, and 19A; and Pneu-P-23 to serotypes 2, 8, 9N, 10A, 11A, 12F, 15B, 17F, 20, 22F and 33F. Non-vaccine type indicates any other serotype, not reflected in the list above.

For 2011, the associated vaccine type that caused the largest number of cases of invasive pneumococcal disease varied by age group. For all ages, Pneu-C-7 serotypes account for the smallest proportion of cases (7%), consistent with an effective vaccination program. Pneu-C-13 serotypes account for a majority (53%) of cases in the 2 to 4 year and age group, whereas Pneu-P-23 serotypes predominated in those aged 15 to 49 years (32%) and 50 to 64 years (27%). For those aged less than 2 years or 65 years and over, invasive disease caused by non-vaccine type serotypes was most common(34 and 33%, respectively). Across all age groups, Pneu-C-13 and Pneu-P-23 serotypes caused the largest burden of disease (26% each), while non-vaccine type followed closely behind (24%).

Overall in 2011, according to NML's Streptococcus Surveillance, Pneu-C-7 serotypes accounted for the smallest proportion of all cases (7%), consistent with an effective vaccination program, while Pneu-C-13 and Pneu-P-23 serotypes caused the largest burden of disease (26% each), followed closely by non-vaccine serotypes (24%) (Figure 2).

Notably in 2011, the associated vaccine type responsible for the largest proportion of cases of IPD varied by age group. Pneu-C-13 serotypes accounted for a majority (53%) of cases in the 2 to 4 year age group, whereas Pneu-P-23 serotypes predominated in those aged 15 to 49 years (32%) and 50 to 64 years (27%). For those aged less than 2 years or 65 years and over, invasive disease caused by non-vaccine type serotypes was most common (34% and 33%, respectively).

As the Pneu-C-13 vaccine was introduced to Canadian jurisdictions from 2010 to 2011, and data presented in Figure 2 captures cases serotyped in 2011, it is not unexpected that a large proportion of Pneu-C-13 cases would occur in those aged 2 to 4 years. Some serotypes the Pneu-C-13 vaccine protects against are known to demonstrate antimicrobial resistance, limiting effective treatment options. Therefore, it will be important to continue monitoring to determine if there is a reduction in incidence over time with the use of Pneu-C-13 vaccine in Canada.

Invasive Pneumococcal Disease Surveillance in Canada

Health professionals in Canada play a critical role in identifying and reporting cases of invasive pneumococcal disease. See the Surveillance section for more information on IPD surveillance in Canada.

Invasive Pneumococcal Disease (IPD) Resources

IPD Publications

IPD Guidelines and Recommendations

Other Resources on IPD

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