Pneumococcal: The Disease & Vaccines
Much like Haemophilus influenzae type b (Hib), pneumococcal bacteria (Streptococcus pneumoniae) affect the most defenseless of the population (infants, toddlers and the elderly). The diseases caused by pneumococcus include meningitis (inflammation of the lining of the brain), bloodstream infections and pneumonia (infection of the lungs). A form of the pneumococcal vaccine was first introduced for use in adults in 1977; a second type of pneumococcal vaccine was introduced for all infants and young children in the United States in 2000. Before the vaccine, every year pneumococcus caused about 700 cases of meningitis, 17,000 cases of bloodstream infections, 200 deaths and 5 million ear infections in children.
Infants and young children are at greatest risk of serious infection because they are unable to develop immunity to the sugar (or polysaccharide) that coats the bacteria, something that older children can do when they are more than 2 years of age.
An ounce of prevention is worth a pound of cure
In the 1940s all of the strains of pneumococcus could be treated with the antibiotic, penicillin. However, over time many pneumococcal strains have become resistant not only to penicillin, but also to other antibiotics developed to combat bacterial infections. “Resistance” means that bacteria have changed, or evolved, so that they are no longer killed by one or more antibiotics. As a result, treatment with those antibiotics is not effective against those resistant strains.
Strains of pneumococcus have now been identified that are highly resistant to most antibiotics. Our reliance on and overuse of antibiotics have led to this resistance, backing us into a corner when treating infections caused by these and other types of bacteria. Unfortunately, we have taken our first steps into a post-antibiotic era. This makes prevention through the use of vaccines all the more important.
The disease
What is pneumococcus?
Pneumococcus is a bacterium that causes several different types of serious infections in children. But by far the most common is pneumonia. Children with pneumonia develop high fever, cough and rapid, difficult breathing. Sometimes the bacteria cause pus to accumulate not only inside the lung, but between the lung and the chest wall (called empyema). Empyema can compress and collapse the lung. Although the vast majority of children with pneumonia recover, the disease is occasionally fatal.
How do you catch pneumococcus?
Pneumococcus is a bacterium that is commonly found lining the surface of the nose and the back of the throat; in fact, about 25 of every 100 people are colonized with pneumococcus. Many children will come in contact with pneumococcus sometime in the first two years of life. Because most adults have immunity to pneumococcus, a mother will passively transfer antibodies from her own blood to the blood of her baby before the baby is born. The antibodies that the baby gets before birth usually last for a few months. However, as these maternal antibody levels diminish, the baby becomes vulnerable. Most children who first come in contact with pneumococcus don't have a problem. But every year, tens of thousands of children suffer severe, often debilitating, and occasionally fatal infections with pneumococcus ─ most of these children were previously healthy and well nourished.
Pneumococcal infections after influenza
Pneumococcus is known as an “opportunistic” infection because it lives in the respiratory tract of people without causing disease, but when the respiratory tract is compromised by an infection such as influenza, the bacteria then invade the lungs (pneumonia), bloodstream (sepsis), or brain and spinal cord (meningitis). Activities like smoking can also disrupt the lining of the nose and throat, allowing for pneumococcal infections and subsequent disease.
Smoking and increased risk of disease
Because smoking disrupts the lining of the throat and lungs, people who smoke are at increased risk of some infections, including pneumococcus and meningococcus. Both of these vaccine-preventable diseases can cause meningitis. Pneumococcus is also a common cause of pneumonia.
Find out more about meningitis in this video discussion between two CHOP doctors.
The vaccine
How is the pneumococcal vaccine made?
There are two types of pneumococcal vaccines. The first type is called a polysaccharide vaccine, often abbreviated “PPSV.” First licensed in 1977, this vaccine contains the sugar (polysaccharide) coating from several types of pneumococcal bacteria. The current version protects against more types of pneumococcus (23 types) than any other pneumococcal vaccine available. It is given to adults and certain high-risk younger people.
Unfortunately, children less than 2 years old don't develop very good immune responses to the polysaccharide vaccine, so infants typically get the second type of pneumococcal vaccine. This version, called the pneumococcal conjugate vaccine (PCV), is made in a manner similar to the vaccine against Haemophilus influenzae type b (Hib; see "How are vaccines made?"). Specifically, the pneumococcal polysaccharides are linked (or conjugated) to a harmless “helper” protein. As children make an immune response to the helper protein, they also make an immune response to the polysaccharides. The end result is that antibodies directed against the pneumococcal polysaccharides protect the child without taking the risk that their first encounter with natural pneumococcus will result in severe illness, permanent disabilities or death. Conjugate vaccines have also been shown to be effective in adults, so they are used in various age groups of people.
An added benefit of the conjugate vaccines is that they also reduce the amount of bacteria in the vaccinated person’s nose, thereby reducing the spread of pneumococcus among families and community members.
What are the side effects of the pneumococcal vaccine?
After receiving the pneumococcal vaccine, people can experience pain or swelling where the shot was given, decreased appetite, irritability, headache or muscle aches. Some will experience a low-grade fever, but a few will develop a higher fever (more than 102 degrees Fahrenheit).
Other questions you might have
Why do pneumococcal vaccines include numbers in the name?
A major challenge in creating pneumococcal vaccines was the number of different types of pneumococcus that can cause illness — about 90 different ones. For this reason, all pneumococcal vaccines protect against several types of the bacteria. The numbers in the name of each pneumococcal vaccine (polysaccharide or conjugate versions) indicate how many types are contained in that particular vaccine (23 for the polysaccharide vaccine and 15 or 20 or 21 for conjugate vaccines).
Is it true that more than one type of infection can cause meningitis?
Yes. Everyone has heard it on the news — the story of a local student infected with meningitis. Such a report inevitably results in many questions and a great amount of concern and even fear among families with children in the affected school.
There are some important considerations when this happens. First, it is important to remember that meningitis refers to an infection that has reached the lining of the brain and spinal cord. Second, it can be caused by viruses or bacteria (hence the reference to viral meningitis or bacterial meningitis).
Viral meningitis, the most common type of meningitis, is often less severe than bacterial meningitis. Vaccine-preventable diseases that can cause viral meningitis include measles, mumps, chickenpox and influenza.
Most, but not all, cases of bacterial meningitis can be prevented by vaccination. The bacteria most often associated with meningitis include meningococcus, pneumococcus, and Haemophilus influenzae type B (often referred to as Hib). Fortunately, by the age of 2, most children are fully immunized against pneumococcus and Hib and most adolescents are protected against meningococcus.
Does the pneumococcal vaccine prevent ear infections in children?
Pneumococcus is a common cause of ear infections in infants and young children. However, other bacteria also cause ear infections in this age group. The pneumococcal vaccine prevents between 6 and 15 of every 100 ear infections caused by pneumococcus.
Which adults should get the pneumococcal vaccine?
Many adults are recommended to get vaccinated against pneumococcal vaccine, but they might not realize it.
Adults 50 years and older who have not been vaccinated against pneumococcus
Adults 50 years and older who have not previously received a pneumococcal vaccine should get either PCV20 alone, PCV21 alone, or PCV15 followed by a dose of PPSV23. In most cases the dose of PPSV23 should be separated by a year, but this interval can be shorter for some people, so individuals should check with their healthcare provider about the timing that is best for their situation.
Adults 50 years and older who were previously vaccinated against pneumococcus
Adults 50 years and older who were previously vaccinated against pneumococcus should talk with their healthcare provider about whether they need the pneumococcal vaccine and if so, which version they need.
Adults 19 to 49 years of age
Adults ages 19 to 49 with immunocompromising conditions, cochlear implants, cerebrospinal fluid leaks, or chronic health conditions such as alcoholism, chronic heart, liver or lung disease, cigarette smoking, or diabetes are at higher risk of suffering complications from pneumococcal infections, and should, therefore, also be vaccinated. People unsure if they need a pneumococcal vaccine should check with their healthcare provider to review their pneumococcal vaccine needs.
Adults in this age group who have already received one or more pneumococcal vaccines should consult with their healthcare provider to determine whether they need additional doses.
Relative risks and benefits
Do the benefits of the pneumococcal vaccine outweigh its risks?
Pneumococcal bacteria still cause hundreds of cases of meningitis, bloodstream infections and pneumonia every year in the United States. Because the pneumococcal vaccine does not cause serious side effects, the benefits of the vaccine clearly outweigh its risks.
Disease risks
- Pneumonia - symptoms can include high fever, cough, and rapid, difficult breathing
- Empyema – pus between lung and chest wall
- Sepsis (bloodstream infections)
- Meningitis (inflammation of the lining of the brain)
- Antibiotics don’t always work
- Disease can be fatal
Vaccine risks
- Pain, redness and swelling at the injection site
- High fever (>102 degrees Fahrenheit) in up to 10 of 100 recipients
- Decreased appetite
- Irritability
- Young children who get pneumococcal vaccine and the inactivated flu vaccine (shot) at the same time may be more likely to experience a seizure associated with high fever, called a febrile seizure. Although scary, febrile seizures do not cause long-lasting effects.
References
Orenstein W, Offit PA, Edwards KM and Plotkin SA. Pneumococcal conjugate vaccine and pneumococcal common protein vaccines, in Vaccines, 8th Edition, 2024, 826-868.
Orenstein W, Offit PA, Edwards KM, and Plotkin SA. Pneumococcal polysaccharide vaccines, in Vaccines, 8th Edition, 2024, 869-889.
Centers of Disease Control and Prevention. Pneumococcal Vaccination: What Everyone Should Know. Oct. 26, 2024.
Reviewed by Lori Handy, MD, MSCE, on March 20, 2025