Why the Burden of Pneumococcal Disease is Underestimated and Misunderstood: Implications for Public Health Planning

Facts

• In 2017-18, pneumonia led to 138,485 emergency department visits across Canada. It was the ninth leading cause of a trip to the ER.[1]
• 45% – 80% of the cases of community acquired pneumonia in adults 50 years or over require hospitalization. [2]
• Due to Canada’s aging population, the number of hospitalized pneumonia cases among the population aged 65 or older is forecasted to double between 2010 and 2025.[3]
• In the 2018-19 season, the most common reason reported by those 65+ for not receiving a pneumococcal vaccine was the view that the vaccine is not necessary. For adults with underlying medical conditions, the most common reason for not receiving the vaccine was that they had never heard of it.[4]
• The 30-day mortality rate following hospitalization for patients with community acquired pneumonia 16 years or older is 12%.[5]

Background

Pneumonia is mainly caused by bacterial and viral infections. Infections caused by Streptococcus pneumoniae (the pneumococcus) include invasive pneumococcal disease (IPD) and community acquired pneumonia (CAP). Many micro-organisms can cause CAP, however S. pneumoniae is the most commonly identified pathogen.

There are two vaccines that offer protection against S. pneumoniae: 23-valent pneumococcal polysaccharide vaccine (PPSV23) and 13-valent pneumococcal conjugate vaccine (PCV13). Studies have found that the combination of PPSV23 and PCV13 produces a greater immune response and offers more protection in adults.[6]

Vaccinating against pneumonia is essential to protecting the lung health of older adults. With COVID-19 heightening the risk for this population, this year, more than ever, it is imperative that Canadians are made aware of the benefits of being immunized and the protection that it offers. There are concerns that preventable infectious diseases may spread once physical distancing measures begin to be lifted. Low uptake of pneumococcal vaccines could lead to increased hospitalizations, straining provincial healthcare system capacity.

Given this, there is a need to bring awareness to the fact that pneumococcal pneumonia is poorly understood, and requires more attention from both medical experts and government. The Lung Health Foundation’s position is twofold: Firstly, many factors are leading to an inaccurate estimate of pneumonia burden in Canada. Second, utilizing this incomplete data in public health planning has resulted in an insufficient approach to prevention.

Why Burden of Disease is underestimated

In Canada, there are several challenges associated with accurately estimating the incidence of pneumococcal pneumonia. Assessment of the true incidence of CAP is difficult due to factors such as: lack of systematic testing for etiologic confirmation, suboptimal sensitivity and specificity of available diagnostic tests[7], atypical disease presentation in older adults, hospital case coding, and lack of a surveillance system.[8] Explanations on a few of these key factors can be found below.

(1) Atypical disease presentation & diagnostic testing

There does not exist a “gold standard” for defining a patient as having CAP. Given the complexities of disease presentation and detection, many CAP patients are going undetected. For instance, elderly patients with CAP often do not exhibit typical symptoms; while most patients will exhibit at least one respiratory symptom, oftentimes they are not tested due to exclusion of certain clinical symptoms considered to be typical.

In addition, while chest x-ray is currently the standard for diagnosing CAP, findings may be absent in certain patient populations. Having secondary diagnosis and imaging review results in many more patients with CAP being identified. Studies have also shown that secondary diagnosis identifies more patients with comorbidities including COPD. As such, the current strategy being used in hospitals is resulting in data that excludes a large portion of patients with chronic illnesses. [9]

LeBlanc et al. (2017) found that among hospitalized patients for CAP, the proportion of cases caused by S. pneumoniae varied between 14.3% and 23.2% depending on the laboratory test used, demonstrating the difficulty of estimating the true disease burden. They also noted a decline in testing in the oldest age groups, where CAP attributed to S. pneumoniae is more common.

(2) Lack of surveillance & non-hospitalized patients

While national surveillance data on IPD exists in some capacity through the Canadian Notifiable Disease Surveillance System, no surveillance exists on the burden of CAP. More robust data on the morbidity, mortality, and burden of CAP patients is desperately needed.[10] This information is integral to working towards better prevention and treatment of CAP and to inform public health planning.

The lack of surveillance means that incidence data is obtained from sources such as administrative datasets or specific clinical investigations. These sources provide only a limited snapshot of CAP incidence in hospitalized patients, and do not accurately take into account non-hospitalized patients. Outpatients can enter the healthcare system through various means including primary care teams, and walk-in clinics. These clinics often have very limited database capabilities and do not track which patients have received a positive pneumonia diagnosis.[11] The incomplete data on incidence undermines the ability for governments to effectively put prevention measures in place.

The Implications on the National Advisory Committee on Immunization (NACI) Recommendations

NACI is responsible for making recommendations on approved vaccines in Canada, including identifying high risk groups that should be the target of vaccinations. The CAP incidence rate used in NACI models does not take into account the nuances explained above, and is much lower than the incidence rate reported within Canadian research. NACI utilizes an incidence rate of 333.4/100,000, while many studies have reported incidence rates of over 1000/1000, 000. McNeil et al (2016) reported a national incidence rate of 1,537/ 100,000 in individuals 65 years or older. [12]

With this, even though Canadian adults aged 50-64 contribute greatly to the burden or illness of community acquired pneumonia, NACI does not recommend the pneumococcal conjugate vaccine in adults of this age groups. Further, while PCV13 has been recommended by NACI for the prevention of IPD and CAP for those over the age of 65 and adults who are immunocompromised, many provincial governments don’t fund the vaccine for all populations under their public immunization programs.

This has significant implications for public health planning as the economic and health impacts of pneumonia continues to be a significant burden on Canadian society. Measures to prevent the spread of community acquired pneumonia are not aligned with the significant burden the disease has. To that end, greater attention needs to be given to the issues around diagnosis and surveillance of pneumonia, as well as the need to implement more comprehensive prevention measures.