“This is a very effective vaccine and a textbook example of herd immunity,” said Nancy M. Bennett, M.D., M.S., professor of Medicine, director of the Center for Community Health at the University of Rochester Medical Center, and deputy director of the Monroe County Department of Public Health. “Even though the vaccine is only given to infants, it has proven highly effective in reducing infections among people who don’t get vaccine, as well as among those who do.”
The pediatric pneumococcal conjugate vaccine, which is marketed under the brand name Prevnar by Wyeth, was introduced in 2000, and a year later the CDC recommended that it be given to all children younger than 2 years. The vaccine was created using a “conjugate” vaccine platform that was developed by URMC pediatric researchers in the 1980s. The process makes a vaccine more effective by linking it to a protein that spurs an infant’s immune system to fight an infection especially vigorously.
Prevnar is designed to provide immunity to 7 serotypes – or strains – of the bacteria streptococcus pneumoniae. While commonly associated with pneumonia and blood infections, pneumococcus is also the most common cause of bacterial meningitis – a potentially life threatening inflammation in the central nervous system.
Bennett – a co-author of the study – oversees the Rochester Emerging Infections Program, one of several sites in a national surveillance and research network funded by the Centers for Disease Control and Prevention (CDC). The network tracks the epidemiology of several bacterial and viral diseases that are preventable by vaccines and evaluates the effectiveness of new vaccines after they have been introduced. The other sites included in the study are Baltimore, Connecticut, Minnesota, Tennessee, San Francisco, Atlanta, and Oregon.
The study included data on 1379 cases of pneumococcal meningitis between 1998 and 2006; 71 of the cases were from the 7-county Rochester region. By the end of the seven-year period, researchers found that incidence of meningitis caused by all serotypes had declined by more than 30% across all age groups. Meningitis caused by the 7 strains in the vaccine declined 73%. The vaccine even reduced infection rates in serotypes of the disease that were related to, but genetically different from the ones targeted by the vaccine.
In a finding that was a cause for concern, the researchers also saw a small increase in disease caused by serotypes that are not included in Prevnar. However, the overall decline in disease far outweighed the small increase in the disease caused by the serotypes not included in the vaccine. Researchers also point out that there are new vaccines under development that may provide protection from these strains.