Article: Prevnar Protects High-Risk Patients

[Guest guest]

Pneumococcal Conjugate Vaccine Protects High-Risk Patients

http://id.medscape.com/18767.rhtml

WESTPORT, Mar 13 (Reuters Health) - A conjugate vaccine containing seven

pneumococcal

serotypes (7-valent vaccine) is more immunogenic in nonresponders than a

23-valent vaccine.

This finding suggests that immunization with a conjugate vaccine will

afford protection to

high-risk patients, according to German authors writing in the March

issue of Infection and

Immunity.

Dr. S. Zielen and colleagues, from Klinikum der Rheinischen

Friedrich-Wilhelms-Universitat in

Bonn, explain that nonresponsiveness is characterized by a defective

immune response to

polysaccharide epitopes in the presence of a normal response to peptide

antigens. Linkage of

polysaccharide antigens to a protein carrier is thought to increase

their immunogenicity and is the

rationale behind the development of new conjugate vaccines.

In the present study, the authors determined the immunogenicity and

tolerance of a 7-valent

conjugate vaccine. They administered two doses of the vaccine, separated

by an interval of 4 to 6

weeks, to 22 infection-prone patients who met criteria for

nonresponsiveness to the 23-valent

pneumococcal polysaccharide vaccine, and to 21 controls.

The investigators report that, compared with controls, patients showed

significantly reduced

immune responses to all pneumococcal serotypes.

According to the paper, the postvaccination immune response was

dependent on serotype: " A

median titer of >1 microgram/mL in patients was recorded only for

serotypes 4, 9V, 14, and

19F, which are known to be more immunogenic than serotypes 6B, 18C, and

23F. " In contrast,

more than 95% of control subjects had a titer of more than 1

microgram/mL to all serotypes.

Dr. Zielen's team notes that, although the 7-valent vaccine stimulated

only low responses in

patients who were nonresponsive to the 23-valent vaccine, the levels of

antibody that it elicited

were higher than those produced by the 23-valent vaccine.

In light of their findings, the authors conclude that " a pneumococcal

conjugate vaccine should

seriously be considered as an important strategy to protect high-risk

patients. "

Infect Immun 2000;68:1435-1440.