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A Look at Each Vaccine: Pneumococcus Vaccine

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 an empyema). The empyema can compress and collapse the lung. Although the vast majority of children with pneumonia recover, the disease is occasionally fatal.

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, bloodstream infections and pneumonia. 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 and 71,000 cases of pneumonia. 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 do naturally over time.

An ounce of prevention is worth a pound of cure

In the 1940s all of the strains of pneumococcus were sensitive to the antibiotic, penicillin. However, over time many strains of pneumococcus have become resistant not only to penicillin, but also to the broader-spectrum antibiotics developed to combat bacterial infections. 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.

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.

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 his/her 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. 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.

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.

What are the side effects of 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.

Which adults should get the pneumococcal vaccine?

The following groups of adults should get the pneumococcal vaccine:

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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.

Infants and high-risk children
Adults 65 years and older and some high-risk adults
Disease Risks Vaccine 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
  • Pain, redness and swelling at the injection site
  • High fever in 1 of 100 infants
  • Fever and muscle aches (1 in 100 people)


Plotkin SA, Orenstein W, and Offit PA. Pneumococcal conjugate vaccine and pneumococcal common protein vaccines and Pneumococcal polysaccharide vaccines in Vaccines, 6th Edition, 2012, 504-572.

Reviewed by: Paul A. Offit, MD
Date: April 2013 

Materials in this section are updated as new information becomes 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.


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