In developing countries, acute respiratory infections, especially community-acquired pneumonias (CAPs), are the leading causes of hospitalization and death among children under five years of age.
More than 95% of all episodes of clinical pneumonia and more than 99% of pneumonia deaths among children under 5 worldwide occur in developing countries.
Pneumococcus caused an estimated 8.9 million cases of pneumonia in 2015, of which 3.5 million were severe or very severe. It is the second agent causing CAP requiring hospitalization, after Respiratory Syncytial Virus (RSV), and the first in number of deaths: approximately 300,000 deaths per year in children under 5 worldwide.
Among the causes of death due to pneumococcal infection, pneumonia represents 81% and meningitis 12%. The global rate of mortality due to pneumococcal disease in 2015 was 45 deaths (29-56) per 100 thousand children <5 years of age.
As for bacterial meningitis in children under 5, there are approximately 1.2 million cases and 180,000 deaths annually. In an analysis published in 2013, the Region of the Americas had the lowest burden of disease worldwide, with an incidence of 17 cases per 100,000 children per year. It is estimated that, globally, more than 90% of bacterial meningitis is caused by S. pneumoniae, H. influenzae and N. meningitidis. Currently, in the Region of the Americas, S. pneumoniae is primarily responsible for bacterial meningitis.
Pneumococcus is a Gram-positive lancet-shaped diplococcus with a polysaccharide capsule external to the wall. According to the capsular antigenic differences, more than 93 serotypes have been identified, of which a limited number cause invasive pneumococcal disease. Serotype identification has varied by geographic region, age, and study period; 6 to 11 of the most common serotypes cause approximately 70% of all invasive infections in children worldwide.
Persons at risk
Susceptibility to pneumococcal infections is universal; that is, everyone is generally susceptible to infections caused by this agent. However, some conditions increase susceptibility to this bacterium, including invasive diseases: age, chronic disease, overcrowding, poverty, active or passive exposure to tobacco smoke and concurrent upper respiratory tract infections. Pneumococcal infection is more frequent between the ages of 2 months and 3 years, although it decreases after 18 months of age. The risk increases again after age 65.
Pneumococcal disease is transmitted directly (person to person) or through contact with nasopharyngeal secretions (droplets) from the person infected.
Distribution and Seasonality
Pneumococcal disease is distributed worldwide and is present in every climate and season. In countries with a temperate climate, an increase in the incidence of pneumococcal pneumonia is seen in winter and in spring.
Immunity can be acquired passively across the placenta or actively through previous infection or immunization.
Prevention and Control
The pneumococcal conjugate vaccine (PCV) was introduced in the Region in the year 2000, initially in Canada and the United States. Currently, there are two conjugate vaccines available: 10 and 13-valent (PCV10 and PCV13), according to the number of different serotypes present.
In 2018, 36 countries and territories in the Region have one of the two pneumococcal vaccines in their regular programs.
Globally, it has been estimated that pneumococcal pneumonia has decreased by more than a third and deaths due to pneumococcal infections by 51% from 2000 to 2015, following the introduction of the pneumococcal conjugate vaccine in many countries.