The Pneumococcal Vaccine

Introduction 

Pneumococcal disease is a serious infection caused by the bacterium Streptococcus pneumoniae¹. It can lead to a range of illnesses from mild infections, like sinusitis and otitis media, to severe diseases such as pneumonia, bacteremia (a blood infection), and meningitis¹. These diseases are particularly dangerous for immunocompromised individuals, those whose immune systems are weakened due to preexisting medical conditions like cancer, HIV, autoimmune disorders, or organ transplants². These infections not only lead to high hospitalization rates and ICU admissions, but also pose increased risks of long-term disabilities and death¹. Despite these threats, many eligible adults in Canada remain unvaccinated, often due to a lack of awareness about their eligibility or personal risk³.

Vaccine Development 

There are two main types of pneumococcal vaccines approved in Canada:

Polysaccharide vaccine: PPSV23 (Pneumovax 23)

• Protects against 23 serotypes of Streptococcus pneumoniae⁴
• Uses purified sugar molecules from the bacterial surface⁵
• Does not produce strong immune memory, so not as effective in young children⁵
• Commonly used in adults, especially those ≥65 or at high risk⁶

Conjugate vaccines: PCV13 (Prevnar 13), PCV15 (Vaxneuvance), PCV20 (Prevnar 20)，PCV21 (Capvaxive)

• Protect against 13, 15, 20 or 21 serotypes, respectively
• Link the sugar molecules to a carrier protein, which boosts the immune response and creates immune memory
• Effective in infants, children, and immunocompromised adults
• Effective in infants, children, and immunocompromised adults
  

In Canada, NACI (Jan 2025) recommends one dose of either Pneu-C-20 (PCV20) or Pneu-C-21 (Capvaxive) for all adults ≥65 and for adults <65 at increased risk, regardless of prior PCV/PPSV23 history; provinces may choose product based on local serotype epidemiology and program factors.

In older adults, the CAPiTA RCT showed 75% efficacy vs vaccine-type IPD and 45% vs first episode vaccine-type non-bacteremic pneumococcal pneumonia for PCV13; meta-analyses estimate ~45% effectiveness of PPSV23 vs PPSV23-type IPD..

Historical Development 

The first polysaccharide pneumococcal vaccines were developed in the 1940s, initially targeting a limited number of serotypes⁷. As scientific understanding of immunology improved, the introduction of conjugate vaccines in the early 2000s revolutionized pneumococcal prevention by offering better protection to children and immunocompromised adults⁸.

Early research on pneumococcal vaccination began in the early 20th century with the development of heat-killed whole-cell formulations around 1909, followed by clinical trials in 1911. Advances in immunology during the mid-20th century led to the introduction of the first polysaccharide vaccines in the 1940s, the 14-valent formulation in the 1970s, and the widely used PPSV23 in 1983⁷. In 1911, trials resumed, but the focus shifted with the introduction of penicillin in the 1940s⁸. The modern 14-valent PPSV emerged in the 1970s, evolving into the 23-valent PPSV23 licensed in 1983⁷. The conjugate vaccine PCV7 was later introduced for infants in the 2000s, followed by PCV13, PCV15, and PCV20⁸.

Who Should Get the Vaccine 

Pneumococcal vaccines are especially important for:

• Seniors aged 65 and older are at higher risk of severe pneumococcal infection. NACI recommends one dose of either PCV20 or PCV21 for all adults in this age group, with additional doses considered only in specific clinical situations.⁹
• Anyone with a weakened immune system, like cancer patients or those living with chronic conditions, who are more likely to get very sick from pneumococcal bacteria⁹. High-risk individuals may be recommended to receive both vaccines in a specific sequence for stronger and longer-lasting protection⁹.
• Young children, especially babies under age 5, who are still building their immune systems and can easily get very sick¹. They will receive pneumococcal vaccines as part of their regular childhood vaccinations, starting at 2 months of age¹

Public Health Benefits

Pneumococcal vaccines have led to major public health improvements, especially among high-risk groups. After the introduction of vaccines like PCV13 and PPSV23, cases of invasive pneumococcal disease (IPD) have dropped significantly in countries with strong immunization programs¹¹. This means fewer people suffer from severe illnesses caused by Streptococcus pneumoniae¹¹.

Additionally, these vaccines also help save lives and reduce hospital visits. A large randomized clinical trial demonstrated that PCV13 significantly reduced the risk of vaccine-type pneumonia and invasive pneumococcal disease in adults aged 65 and older, leading to fewer severe illness episodes and less demand on hospital resources.¹²

Another benefit is indirect protection, sometimes called herd effects. Widespread use of pneumococcal conjugate vaccines reduces circulation of vaccine-covered serotypes, which helps protect vulnerable groups. However, serotype replacement has also been observed, highlighting the importance of higher-valency vaccines like PCV20 and PCV21.⁹ Over time, this creates healthier communities and helps prevent outbreaks of preventable diseases⁹.

Vaccine Hesitancy
Despite strong recommendations, many Canadians, especially those who are immunocompromised, remain unvaccinated against pneumococcal disease. A large part of this problem comes down to awareness. Many people simply don’t realize they’re at higher risk, particularly if their condition isn’t outwardly visible or if they’re younger adults who don’t see themselves as vulnerable³. Even when they qualify, they may not know the vaccine exists or that it’s publicly funded in some provinces. Another issue is that healthcare providers sometimes miss the opportunity to recommend the vaccine, which surveys have shown to be one of the strongest influences on whether a person actually gets it³.

Alongside knowledge gaps, misinformation and mistrust also contribute to low uptake. Some individuals have doubts about vaccine safety, often due to online misinformation or past controversies surrounding vaccines in general¹¹. Others, especially from marginalized or low-income communities, may distrust healthcare systems because of past experiences of neglect, bias, or poor access to care. Language barriers, low health literacy, and cultural disconnects can also leave patients confused about vaccine benefits or unsure about where to go. For many, the issue isn’t unwillingness; it’s that the information doesn’t reach them clearly or reliably. Without better communication, trust-building, and outreach, especially in underserved communities, vaccine hesitancy will continue to stand in the way of better public health¹¹.

Digital Outreach Potential

Digital health tools offer a promising way to address the persistent gaps in adult pneumococcal vaccination. By using technology to connect patients and providers at the right time, these interventions can boost awareness, increase follow-through, and make vaccination more accessible. Proven strategies include:

• SMS or email reminders: Automatically notify patients when they are due for a pneumococcal vaccine or are newly eligible¹³.
• EMR (electronic medical record) alerts: Prompt clinicians to discuss and offer vaccination when high-risk patients come in for care¹³.
• Online portals and mobile apps: Allow individuals to check their vaccine eligibility, access educational content, and book appointments at local clinics¹⁴.
• Centralized digital registries: Track vaccination history across systems and support coordinated outreach campaigns¹³

A 2023 study in Israel demonstrated how combining these tools, reminders, led to a significant rise in pneumococcal vaccination among immunocompromised patients¹³. If Canada implements a similar model across provinces, digital outreach could play a key role in eliminating preventable disease gaps in adult immunization.

Reference：

1. Centers for Disease Control and Prevention. “Pneumococcal Disease.” CDC.gov, https://www.cdc.gov/pneumococcal/.
   
2. Public Health Agency of Canada. Protecting Vulnerable Canadians: Pneumococcal Vaccination Report. 2023.
   
3. Public Health Agency of Canada. Realizing the Future of Vaccination for Public Health. 2024, https://www.canada.ca/en/public-health/corporate/publications/chief-public-health-officer-reports-state-public-health-canada/state-public-health-canada-2024/report.html.
   
4. Centers for Disease Control and Prevention. “Types of Pneumococcal Vaccines.” CDC.gov, https://www.cdc.gov/pneumococcal/vaccines/types.html.
   
5. Pfizer. “Understanding Six Types of Vaccine Technologies.” Pfizer.com, https://www.pfizer.com/news/articles/understanding_six_types_of_vaccine_technologies#:~:text=Conjugate%20vaccines%20are%20the%20same,Scully%20says.
   
6. Systematic Review and Meta-Analysis of the Efficacy and Effectiveness of Pneumococcal Vaccines in Adults. [Full publication details needed for MLA formatting.]
   
7. Musher DM, Anderson R, Feldman C. The remarkable history of pneumococcal vaccination: an ongoing challenge. Pneumonia (Nathan). 2022 Sep 25;14(1):5. doi: 10.1186/s41479-022-00097-y. PMID: 36153636; PMCID: PMC9509586..
   
8. Hausdorff, William P., et al. “Pneumococcal Conjugate Vaccine Early Impact.” Vaccine, vol. 29, no. 18, 2011, pp. 3367–3372. https://www.sciencedirect.com/science/article/pii/S0954611111002423.
   
9. Public Health Agency of Canada. Canadian Immunization Guide: Pneumococcal Vaccine. 2025, https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-4-active-vaccines/page-16-pneumococcal-vaccine.html.
   
10. Langley, Joanne M., et al. “Implementation of Pneumococcal Conjugate Vaccine in Canada.” Canadian Medical Association Journal, vol. 175, no. 5, 2006, https://pmc.ncbi.nlm.nih.gov/articles/PMC2095050/.
    
11. Stratoberdha, Doris, et al. “Barriers to Adult Vaccination in Canada: A Qualitative Systematic Review.” Canadian Pharmacists Journal, vol. 155, no. 4, 2022, pp. 206–218. https://doi.org/10.1177/17151635221090212.
    
12. Bonten, Marc J. M., et al. “Polysaccharide Conjugate Vaccine against Pneumococcal Pneumonia in Adults.” New England Journal of Medicine, vol. 372, no. 12, 2015, pp. 1114–1125. https://www.nejm.org/doi/full/10.1056/NEJMoa1408544.
13. Shapiro Ben David, S., et al. “A Nationwide Digital Multidisciplinary Intervention Aimed at Promoting Pneumococcal Vaccination in Immunocompromised Patients.” ResearchGate, 2023, https://www.researchgate.net/publication/373090068.
    

by Angela Zhang