Systematic review on serotypes distribution of pneumococcal pneumonia in adults and the elderly

Pneumococcal pneumonia is a major cause of morbidity and mortality among adults, especially those over 65 years of age. Understanding pneumococcal serotype-specific epidemiology in adults and elderly is necessary to inform vaccination policies and to guide the inclusion of serotypes in pneumococcal vaccines. This study aimed to identify the serotypes causing pneumonia in the elderly.

A systematic review search was performed using the PubMed database from 1984 to 2020. The search was limited to articles written in English. Studies assessing pneumococcal pneumonia in adults were included. Meta-analysis, other systematic literature reviews and case-reports were excluded. Studies published after the introduction of vaccines (PPSV23 and PCVs) were included.

Forty studies were included. The most common serotype identified in the majority of the articles in adults was the serotype 3 followed by serotypes 19A and 11A. Those serotypes are included in current vaccines. Emergence of non-vaccine serotypes was also observed.

Pneumococcal pneumonia remains a high burden in the elderly despite the existence of vaccines for many years. In 2019, nearly 1.4 million deaths were attributable to pneumococcal pneumonia (50% of whom were over 70 years old) and was the leading cause of deaths from infectious disease worldwide. The study highlights the importance of constant monitoring serotypes emerging in this population to better target vaccination strategies.