Immunogenicity of pneumococcal revaccination in patients with chronic disease.

BACKGROUND: To prevent serious pneumococcal infections, 23-valent pneumococcal polysaccharide vaccine is recommended for individuals over 24 months of age with chronic predisposing diseases and for healthy older adults. This nonrandomized controlled study in rural Alaska assessed the immunogenicity of revaccination in adults. METHODS: Twenty-six adults, 33 to 88 years of age, vaccinated a mean of 7.4 years before this study, were matched to 26 previously unvaccinated subjects by age, number of chronic diseases, sex, and ethnicity. One or more chronic diseases were validated in 62% of subjects (32 of 52). All received a first or second intramuscular dose of pneumococcal vaccine. Antibody levels were determined by radioimmunoassay for 12 pneumococcal capsular serotypes immediately before and 20 to 84 days after vaccination. RESULTS: Six to 9 years after primary vaccination, over one third of serotype-specific antibody levels were below 500 ng of antibody nitrogen per milliliter, equal to the percentage in unvaccinated subjects of similar age. Antibody levels against all pneumococcal serotypes rose to similar levels after primary vaccination and revaccination, and 54% and 55%, respectively, of subjects who received primary vaccination and revaccination had at least a 1.4-fold increase in antibody levels. Only the antibody level for serotype 4 remained low. Neither gender nor age affected peak response. For those with chronic diseases, there was a trend toward fewer low antibody levels against three or more serotypes after revaccination (two subjects [13%]) than after primary vaccination (five subjects [31%]). CONCLUSIONS: Following the initial immunization of high-risk and elderly patients with pneumococcal polysaccharide, pneumococcal antibody levels appear to wane with time. Primary vaccination and revaccination 6 or more years after a first dose of pneumococcal vaccine stimulate comparable mean antibody levels.

Pneumococcal vaccination in a remote population of high-risk Alaska Natives.

In response to an increasing prevalence of serious pneumococcal disease among adult Alaska Natives of northwest Alaska, a 3-year program was begun in 1987 to identify residents of that remote region who were at high risk for developing invasive pneumococcal disease, to determine their pneumococcal vaccination status, and to deliver vaccine to at least 80 percent of those at risk. After reviewing public health nursing and Indian Health Service data bases, the authors identified 1,337 persons, 20 percent of the 6,692 residents of the region, at high risk for invasive pneumococcal infection, defined either by having a specific chronic disease or by age criteria. Cardiovascular disease and alcoholism were the two most common chronic diseases. Only 30 percent of those determined to be at high risk had received one or more doses of pneumococcal vaccine previously. Half of those persons had received their most recent vaccination 6 or more years earlier. The program used both customary and innovative methods to deliver 23-valent polysaccharide vaccine to 1,046 of those at high risk (78 percent), including 388 persons who were revaccinated. At the completion of the project, 1,123 persons, 84 percent of those at high risk, had received at least 1 dose. They included 1,088 persons, 81 percent of those at high risk, with vaccination within the previous 5 years as a result of the project, compared with a 15-percent rate prior to the vaccination phase of the project. The program demonstrated that high levels of vaccination against pneumococcal disease, exceeding Year 2000 objectives of 60 percent, are attainable in a remote rural Alaskan population.