Questions & Answers

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What causes pneumococcal disease?
Pneumococcal disease is caused by Streptococcus pneumoniae, a bacterium. There are more than 90 subtypes. Most subtypes can cause disease, but only a few produce the majority of invasive pneumococcal infections. The 10 most common subtypes cause 62% of invasive disease worldwide.

How does pneumococcal disease spread?
The disease is spread from person to person by droplets in the air. The pneumococci bacteria are common inhabitants of the human respiratory tract. They may be isolated from the nasopharnyx of 5%-70% of normal, healthy adults.

How long does it take to show signs of pneumococcal disease after being exposed?
As noted above, many people carry the bacteria in their nose and throat without ever developing invasive disease. The incubation period for specific diseases caused by an invasive pneumococcal infection is noted below.

What diseases can pneumococci bacteria cause?
There are three major conditions caused by invasive pneumococcal disease: pneumonia, bacteremia, and meningitis. They are all caused by infection with the same bacteria, but have different symptoms.

Pneumococcal pneumonia (lung disease) is the most common disease caused by pneumococcal bacteria. It is estimated that 175,000 hospitalizations due to pneumococcal pneumonia occur each year in the United States. The incubation period is short (1-3 days). Symptoms include abrupt onset of fever, shaking chills or rigors, chest pain, cough, shortness of breath, rapid breathing and heart rate, and weakness. The fatality rate is 5%-7% and may be much higher in the elderly.

Pneumococcal bacteremia (blood infection) occurs in about 25%-30% of patients with pneumococcal pneumonia. More than 50,000 cases of pneumococcal bacteremia occur each year in the United States. Bacteremia is the most common clinical presentation among children younger than age two years, accounting for 70% of invasive disease in this group.

Pneumococci cause 13%-19% of all cases of bacterial meningitis (infection of the covering of the brain or spinal cord) in the United States. There are 3,000-6,000 cases of pneumococcal meningitis each year. Symptoms may include headache, tiredness, vomiting, irritability, fever, seizures, and coma. Children younger than age one year have the highest rate of pneumococcal meningitis, approximately 10 cases per 100,000 population. The case fatality rate is high (30% overall, up to 80% in the elderly).

Pneumococci are also a common cause of acute otitis media (middle ear infection). Approximately 28%-55% of such ear infections are caused by S. pneumoniae. In the U.S., there are 4.9 million cases of otitis media each year in children younger than age five years. Middle ear infections are the most frequent reason for pediatric office visits in the United States, resulting in more than 20 million visits annually.

How serious is pneumococcal disease?
Pneumococcal disease is a serious disease that causes much sickness and death. In fact, pneumococcal disease kills more people in the United States each year than all other vaccine-preventable diseases combined. More than 50,000 cases and more than 10,000 deaths from invasive pneumococcal diseases (bacteremia and meningitis) are estimated to have occurred in the United States in 2002. More than half of these cases occurred in adults for whom pneumococcal polysaccharide vaccine was recommended. Young children and the elderly (individuals younger than age five years as well as those older than age 65 years) have the highest incidence of serious disease.

Case-fatality rates are highest for meningitis and bacteremia, and the highest mortality occurs among the elderly and patients who have underlying medical conditions. Despite appropriate antimicrobial therapy and intensive medical care, the overall case-fatality rate for pneumococcal bacteremia is about 20% among adults. Among elderly patients, this rate may be as high as 60%.

Before a vaccine was available in the United States, pneumococcal disease caused serious disease in children younger than age five years. Each year it was responsible for causing 700 cases of meningitis, 17,000 blood infections, five million ear infections, and 200 deaths. Children younger than age two years are at the highest risk for serious pneumococcal disease.

Is there a treatment for pneumococcal disease?
Penicillin is the drug of choice for treatment of pneumococcal disease; however, resistance to penicillin and other antibiotics has been on the rise. Studies indicate that in some areas of the United States up to 40% of invasive pneumococci are resistant to common antibiotics. Treating patients infected with resistant organisms requires expensive alternative antimicrobial agents and may result in prolonged hospital stays.

The increased difficulty of treating this serious bacterial infection makes prevention through vaccination even more important.

How long is a person with pneumococcal disease contagious?
The exact period of communicability is not known. It appears that transmission can occur as long as the organism remains in respiratory secretions.

How common is pneumococcal disease in the United States?
Healthcare providers are not required by law to report pneumococcal disease to health authorities, so exact numbers are not known. Estimates have been made from a variety of population studies, however, and it is believed that 45,000 cases of invasive pneumococcal disease (meningitis and blood infections) occur each year in the United States. (Pneumonia and middle ear infections are most common but are not considered "invasive" diseases.) The incidence of the disease varies greatly by age group. The highest rate of invasive pneumococcal disease occurs in young children, especially those younger than age two years. Children with certain chronic diseases (e.g., sickle cell disease or HIV infection) are at very high risk of invasive disease.

Can you get pneumococcal disease more than once?
Yes. There are more than 90 known subtypes of pneumococcus bacteria, with 23 subtypes included in the current pneumococcal polysaccharide (adult) vaccine and 7 subtypes included in the current conjugate (child) vaccine. Having been infected with one type does not always make the patient immune to other types. Even if an individual has had one or more episodes of invasive pneumococcal disease, he or she needs to be vaccinated.

Questions and answers about pneumococcal vaccine

Technically reviewed by the Centers for Disease Control and Prevention, May 2007