Prevnar Vaccine Further Reducing Childhood Infections

A vaccine introduced just four years ago is reducing the incidence of some of very serious childhood illnesses. The pneumococcal conjugate vaccine PCV7 (Prevnar) was FDA-approved for use in children in 2000 and has gained a strong following since then. The organism it fights is called Streptococcus pneumoniae, or pneumococcus. It is a leading cause of serious illness among young children worldwide, and is the most frequent cause of pneumonia, bacteremia (infection of the blood), sinusitis, and acute otitis media (middle ear infection).

The US Centers for Disease Control and Prevention reports that in the US alone, Streptococcus pneumoniae causes approximately 17,000 infections per year among children under the age of 5, including 700 cases of meningitis and 200 deaths.

Advantages
Peter L. Havens, MD, MS, Professor of Pediatrics and Epidemiology at the Medical College of Wisconsin, explains the difference between Prevnar and previously used vaccines.

The Prevnar vaccine, he says, is made with the outer sugar coating of the Streptococcus pneumoniae organism. This outer sugar coating is called the capsule, and since it is made of a sugar, it is called a polysaccharide capsule. "The exciting thing about Prevnar is that it conjugates, or couples, the polysaccharide capsule from the Streptococcus pneumoniae with a protein that stimulates the immature immune system of an infant," he explains. "The baby then makes its own antibody to the pneumococcal polysaccharide."

The old pneumococcal vaccine, on the other hand, was made only of the polysaccharide capsule. "While it was approved for adults and children, and included 23 different serotypes (strains) in the vaccine, it did not stimulate a good immune response in children under age two, who cannot respond to a pure sugar antigen," Dr. Havens notes. "The Prevnar vaccine includes seven of the pneumococcal serotypes, but the seven that are included are responsible for the majority of invasive pneumococcal infections in infants."

Effectiveness
Dr. Havens reports, "The Prevnar vaccine is expected to prevent 88% of cases of bacteremia, 82% of cases of meningitis, and 71% of cases of otitis media episodes in the United States in children under six years of age. The vaccine is 97% protective against invasive pneumococcal disease caused by vaccine serotypes in fully vaccinated children."

Since the highest rates of invasive pneumococcal disease occur among young children, especially those under 2 years of age, Prevnar is currently being recommended for children only, but studies in adults are ongoing.

"In general, Prevnar is recommended to be given at 2, 4, 6, and 12-15 months of age for newborn infants," says Dr. Havens. The CDC Advisory Committee on Immunization Practices (ACIP) recommends that the vaccine be used for all children aged 2- 23 months and for older children aged 24-59 months who are at increased risk for pneumococcal disease (such as children with sickle cell disease, human immunodeficiency virus infection, and other immunocompromising or chronic medical conditions).

Shortages Possible
"Overall," notes Dr. Havens, "this is a very exciting vaccine which should allow for a reduction in bacterial meningitis similar to that which was seen with the introduction of the conjugate Haemophilus influenza vaccine in the late 1980s."

The only problem Dr. Havens can see regarding the Prevnar vaccine is its popularity. The manufacturer currently has a shortage of the vaccine, leading the CDC, the ACIP, the American Academy of Family Physicians and the American Academy of Pediatrics to recommend that healthcare providers temporarily suspend the third and fourth doses of PCV7 until more can be made. Children at increased risk of severe disease should continue to receive the routine 4-dose series.

"Vaccines in general have the highest benefit to risk ratio of almost anything that we do in medicine," says Dr. Havens. "Universal vaccination in the United States is an important public health goal. Vaccinating children is the best way to insure the health of each child and the overall health of the community."

P.J. Early
HealthLink contributing Writer

This article includes information from the US Centers for Disease Control and Prevention (CDC).

For more information on this topic, see the HealthLink article The Facts about Vaccines for Children/Recommended 2004 Childhood and Adolescent Immunization Schedule and the website of the Wisconsin Immunization Program.

For more information on recommendations in case of Prevnar shortage, see the CDC press release from March, 2004.

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.