A Look at Each Vaccine: Pneumococcal Vaccine

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). The pneumococcal vaccine was first introduced for use in all infants 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 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 invades the lungs (pneumonia), bloodstream (sepsis), or brain and spinal cord (meningitis). Activities like smoking can also disrupt the lining of the nose and throat and allow 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?

Like the Hib vaccine, the pneumococcal vaccine is made from the sugar coating (polysaccharide) of the bacteria. Antibodies directed against the pneumococcal polysaccharide protect the child without having to take the risk that their first encounter with natural pneumococcus will result in permanent disabilities or death.

Unfortunately, children less than 2 years old don't develop very good immune responses to this polysaccharide alone. So the pneumococcal vaccine was made in a manner similar to the Hib vaccine (See "How are vaccines made?"). The pneumococcal polysaccharide is linked to a harmless protein. This version of the vaccine is referred to as the pneumococcal conjugate vaccine. Once linked, young children are able to make an immune response to the polysaccharide. The big difference between the pneumococcal vaccine and the Hib vaccine is the number of different types of polysaccharides that need to be included in the vaccine. Whereas, there is really only one strain of Hib that causes disease in children, there are about 90 different strains of pneumococcus. Fortunately, most of the serious disease in young children is caused by the 13 strains of pneumococcus contained in the vaccine.

The pneumococcal vaccine was found to be highly effective in preventing severe pneumococcal infection (meaning meningitis, bloodstream infections and pneumonia) in a large trial of children injected with the vaccine. About 40,000 children were included in the initial trial of the vaccine. Since its licensure, the pneumococcal vaccine has been given to millions of children safely.

A second type of pneumococcal vaccine, known as the pneumococcal polysaccharide vaccine, protects against more types of pneumococcus (23 types), but does not include the harmless protein, so it is mostly used only in older adults or those at higher risk for pneumococcus.

What are the side effects of the pneumococcal vaccine?

After receiving the pneumococcal vaccine, children commonly will have pain or swelling where the shot is given and occasionally low-grade fever. About 1 of every 100 children will develop a high fever.

Side effects from the polysaccharide version used in adults include tenderness and redness at the injection site, and about 1 of every 100 people will get a fever and experience muscle aches.

Other questions you might have

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 about 7 of every 100 ear infections and about 20 of every 100 severe ear infections requiring tubes.

Which adults should get the pneumococcal vaccine?

The following groups of adults should get both types of the pneumococcal vaccine (conjugate and polysaccharide):

  • Adults 65 years and older because they are at high risk of pneumococcal infections
  • Adults without a functioning spleen
  • Adults who are immune compromised by disease, chemotherapy or steroids
  • Individuals who are HIV positive

The following groups of adults should get the polysaccharide pneumococcal vaccine regardless of age:

  • Adults who smoke or suffer from alcoholism
  • Adults with heart or lung disease, liver disease, asthma, diabetes or cancer

Read a personal story»

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 infants
  • 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.


Plotkin SA, Orenstein W, Offit PA, and Edwards KM. Pneumococcal conjugate vaccine and pneumococcal common protein vaccines and Pneumococcal polysaccharide vaccines in Vaccines, 7th Edition, 2018, 773-815.

Centers of Disease Control and Prevention. Pneumococcal Vaccination: What Everyone Should Know. Nov. 21, 2019.

Reviewed by Paul A. Offit, MD on May 11, 2020

Materials in this section are updated as new information and vaccines become available. The Vaccine Education Center staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family's personal health. You should not use it to replace any relationship with a physician or other qualified healthcare professional. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult your physician or, in serious cases, seek immediate assistance from emergency personnel.