Greater Benefits of Pneumococcal Vaccines that 'Cover' More Strains

The current vaccine against pneumococcal bacteria is effective, but vaccines that "cover" additional strains could further reduce pneumococcal infections in infants and toddlers, according to an Israeli study in the April issue of the Pediatric Infectious Disease Journal.

Vaccines covering more strains would be especially effective in preventing infections with antibiotic-resistant pneumococci, according to the study by Dr. Dror S. Shouval and colleagues of Ben-GurionUniversity of the Negev, Beer-Sheva, Israel.

The researchers analyzed types and causes of pneumococcal infections among children under age three in the Negev region of southern Israel from 2000 to 2004, before the introduction of pneumococcal vaccine. In Israel and other countries, including the United States, children now receive a "7-valent" vaccine (PCV7) that protects against seven of the most common pneumococcal strains.

Infection with pneumococci (Streptococcus pneumonia bacteria) is a serious public health problem, especially in infants and young children. Pneumococcal vaccine is recommended to prevent "invasive" infections such as pneumonia (infection of the lungs) and meningitis (infection of the tissues lining the brain and spinal cord). Less serious but more common infections, including acute conjunctivitis (eye infection) and acute otitis media (middle ear infection), are also caused by pneumococci.

The researchers analyzed nearly 5,500 pneumococcal strains isolated from children with invasive infections, otitis media, or conjunctivitis or from healthy children. The results suggested that PCV7 vaccination would have prevented infections with 37 percent to 54 percent of strains, depending on the type of isolate.

Vaccines that provided coverage against more pneumococcal strains would afford greater protection. A "10-valent" vaccine (PCV10) designed to cover 10 different strains would have protected the children against 44 to 68 percent of strains. A "13-valent" vaccine (PCV13) covering 13 strains would have prevented infection with 54 to 84 percent of strains identified.

Vaccines with greater coverage would also reduce the risk of infection with strains resistant to penicillin and other common antibiotics. Shouval and colleagues estimate that upgrading from the PCV7 to the PCV13 vaccine could prevent more than 90 percent of cases of invasive pneumococcal disease and acute otitis media caused by drug-resistant pneumococci—including difficult to treat multidrug-resistant strains.

In the United States, routine vaccination with PCV 7 has led to a dramatic reduction in invasive pneumococcal disease, and some reduction in otitis media caused by pneumococci. As the PCV-10 and PCV-13 vaccines are readied for clinical development, there is a need for more information on how coverage against more strains would affect rates of pneumococcal disease.

The new study—including data on less-serious infections—indicates that the newer vaccines are likely to protect against a broader range of pneumococcal strains. The results suggest significant added benefits of both the PCV10 and PCV13 vaccines. "Moreover, PCV13 has an important potential added benefit over PCV7 and PCV10 in reducing disease by drug-resistant S. pneumonia," the researchers conclude.