What is a pneumococcal infection?

Pneumococcal infection refers to a range of diseases caused by *Streptococcus pneumoniae* (肺炎鏈球菌). This bacterium can reside in the human body, often colonizing the upper respiratory tract. Even healthy individuals may be asymptomatic carriers of pneumococcus, yet they can transmit the bacteria to others through respiratory droplets, oral contact, or interaction with objects contaminated by respiratory secretions.

The primary transmission routes of *Streptococcus pneumoniae* include droplet spread and indirect contact. When an infected person coughs, sneezes, or speaks, the bacteria are dispersed into the air in small droplets, easily inhaled by those in close proximity. Additionally, sharing cups, utensils, or other contaminated items can serve as a vehicle for bacterial transmission. This makes children, the elderly, and individuals with compromised immune systems particularly vulnerable high-risk groups.

Clinically, diseases caused by pneumococcus vary widely. In most cases, it leads to milder infections such as otitis media (middle ear infection) or sinusitis, which can typically be alleviated with short-term antibiotic treatment. However, when the bacteria invade the lower respiratory tract or bloodstream, the condition can rapidly worsen, resulting in severe pneumonia, invasive pneumococcal bacteremia, meningitis, or even sepsis. For children and the elderly, these invasive infections tend to be more severe, with significantly higher rates of complications and mortality.

Differences between the 13-valent and 23-valent vaccines

To prevent these severe infections, scientists and public health experts have developed several vaccines to combat pneumococcal infections. The primary preventive vaccines include the 13-valent pneumococcal conjugate vaccine (PCV13, '13價肺炎球菌結合疫苗') and the 23-valent pneumococcal polysaccharide vaccine (23vPPV, '23價肺炎球菌多醣疫苗'). The 13-valent pneumococcal conjugate vaccine combines protein carriers with polysaccharide antigens, offering protection not only against invasive pneumococcal diseases but also against non-invasive conditions like otitis media and sinusitis caused by pneumococcus. This vaccine is commonly recommended for children under 2 years old, with a typical schedule involving doses at 2 and 4 months of age, followed by a booster dose around 1 year old, to establish robust and long-lasting immune protection.

Who needs pneumococcal vaccination?

On the other hand, the 23-valent pneumococcal polysaccharide vaccine covers a broader range of serotypes, theoretically providing more extensive protection, particularly against invasive pneumococcal diseases. However, its effectiveness against non-invasive pneumonia is more limited. Consequently, physicians often tailor vaccination strategies based on age and health status. For high-risk individuals aged 2 years and older, the Scientific Committee recommends initial vaccination with the 13-valent pneumococcal conjugate vaccine (PCV13), followed by the 23-valent pneumococcal polysaccharide vaccine (23vPPV) a year later, to achieve optimal protection.

Vaccination not only effectively reduces the risk of infection for individuals but also fosters herd immunity within communities, decreasing opportunities for bacterial transmission. As more people receive these vaccines, the incidence of severe pneumonia, meningitis, or sepsis declines significantly, substantially alleviating the burden on healthcare systems. This immune barrier is particularly crucial for children, the elderly, and those with weakened immune systems, who are among the most vulnerable to pneumococcal infections and their complications.

In addition to vaccination, good personal hygiene and a sanitary public environment are vital measures for preventing pneumococcal spread. Frequent handwashing, maintaining respiratory hygiene, and avoiding close contact with individuals exhibiting respiratory symptoms are effective strategies to lower infection risk. Furthermore, in crowded settings such as healthcare facilities and schools, regular environmental disinfection and health education can help curb the spread of pneumococcus among populations.

In summary, pneumococcal infection poses a serious threat to public health, with clinical manifestations ranging from mild otitis media and sinusitis to severe pneumonia, meningitis, or sepsis. Vaccination with the 13-valent pneumococcal conjugate vaccine and the 23-valent pneumococcal polysaccharide vaccine effectively reduces the incidence of infections and severe cases, offering protection to children, the elderly, and high-risk groups. As vaccination programs expand, the resulting herd immunity will further diminish bacterial transmission, yielding long-term, positive impacts on overall public health.