Serotypes 3, 19A Most Common for Pneumococcal Community-Acquired Pneumonia


Pneumococcal serotype 3 was prevalent regardless of vaccination status, with the most common cases being in those with chronic lung disease.

Despite vaccination with pneumococcal polysaccharide vaccine (PPSV23, Pneumovax 23; Merck), serotypes 3 and 19A were still the most common serotypes of pneumococcal community-acquired pneumonia (pCAP) among children and older adults, according to results of a new study.

Vial of Pneumococcal vaccine | Image Credit: Bernard Chantal -

Bernard Chantal -

In the study, conducted in South Korea, PPSV23 vaccination could still reduce the risk of mortality among those with pCAP. Investigators of the study noted that even though the targeted risk population has been vaccinated against pneumococcal diseases, the serotypes are still evolving in South Korea, which can affect the rollout of the vaccines.

In the study, individuals aged 19 and older with community-acquired pneumonia (CAP) were included between September 2018 and July 2021. The individuals were from 5 university hospitals in South Korea. A total of 5009 individuals, with a mean age of 70.3 years and 63.1% men, were included. Approximately 71.3% had at least 1 comorbidity and 44.4% and 7.7% were vaccinated with PPSV23 and pneumococcal conjugate vaccine 13, respectively.

The study investigators analyzed data around demographic and clinical characteristics of the individuals, pneumococcal serotype distribution, and risk factors of 30-day mortality of patents with pCAP. They specifically analyzed the clinical characteristics of serotype 3 pCAP.

The study authors said that the leading cause of CAP was Streptococcus pneumoniae with 11.8% in the overall population and 17.7% in individuals less than 65 years of age with chronic medical conditions. Among the 280 serotypes of Streptococcus pneumococcus, the study authors reported that serotype 3 was most common at 10%, followed by 19A, 34, and 35B at 8.9% each.

Investigators also found that the proportion of pCAP was significantly higher in those who were male, those with comorbidities, those in long-term care facility residence, and concomitant respiratory viral infections when compared to non-pCAP infection.

Among 180 individuals who were vaccinated with PPSV23, the non-vaccine serotypes 35B and 34 were the most prevalent at 13.9% and 12%, respectively. There were no differences between the 2 vaccination groups. However, serotype 3 was still prevalent, regardless of vaccination status, and the most common in those with chronic lung disease. Serotype 3 was also more common in the spring at 50%.

Furthermore, the investigators found that advanced age, long-term care facility residence, and bacteremia were all independent risk factors that contributed to mortality for those with pCAP.

The study authors said that S. pneumoniae was most prevalent for those less than 65 years of age with chronic medical conditions, noting that the vaccine uptake rate in this group was low. Further, individuals who received PPSV23 had lower rates of pCAP caused by PPSV23 or 20-valent pneumococcal conjugate vaccine serotypes when compared to individuals who were not vaccinated. They suggested that vaccination with PPSV23 could potentially lower the 30-day mortality risk for patients.

Additionally, the investigators stated, that their study demonstrating that pneumococcus was the most common cause of CAP, was consistent with studies in the United States, Canada, and Italy.

The study authors also added that there were limitations to the study. Serotyping data was limited, with information about only 280 of the 598 cases being available. Further, reparatory viral PCR tests were conducted in only 35.2% of individuals.


Hyun H, Jang AY, Suh JW, Bae IG, et al. Community-Acquired Pneumococcal Pneumonia in Highly Vaccinated Population: Analysis by Serotypes, Vaccination Status, and Underlying Medical Conditions. J Korean Med Sci. 2023 Sep;38(42):e330. doi:

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