Investigation of different group A immunoassays following one dose of meningococcal group A conjugate vaccine or A/C polysaccharide vaccine in adults.

A double-blind, randomized, controlled phase I study to assess the safety, immunogenicity, and antibody persistence of a new group A conjugate vaccine (PsA-TT) in volunteers aged 18 to 35 years was previously performed. Subjects received one dose of either the PsA-TT conjugate vaccine, meningococcal A/C polysaccharide vaccine (PsA/C), or tetanus toxoid vaccine. The conjugate vaccine was shown to be safe and immunogenic as demonstrated by a standardized group A-specific immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) and by a serum bactericidal antibody (SBA) assay using rabbit complement (rSBA). This report details further analysis of the sera using four additional immunologic assays to investigate the relationship between the different immunoassays. The immunoassays used were an SBA assay that used human complement (hSBA), a group A-specific IgG multiplexed bead assay, and two opsonophagocytic antibody (OPA) assays which used two different methodologies. For each vaccine group, geometric mean concentrations or geometric mean titers were determined for all assays before and 4, 24, and 48 weeks after vaccination. Pearson's correlation coefficients were used to assess the relationship between the six assays using data from all available visits. An excellent correlation was observed between the group A-specific IgG concentrations obtained by ELISA and those obtained by the multiplexed bead assay. hSBA and rSBA titers correlated moderately, although proportions of subjects with putatively protective titers and those demonstrating a > or = 4-fold rise were similar. The two OPA methods correlated weakly and achieved only a low correlation with the other immunoassays. The correlation between hSBA and group A-specific IgG was higher for the PsA-TT group than for the PsA/C group.

Prevention of community-acquired pneumonia.

Preventive measures against CAP are important yet underused. Cost-effective preventive measures against CAP include influenza and pneumococcal vaccines, especially in patients over the age of 65 and other high-risk groups. There are now two antiviral agents, amantadine and rimantadine, that can be used both for prophylaxis and for therapy of influenza A virus infections to decrease the morbidity and mortality of this major predisposer of CAP. Because of fewer side effects, rimantadine should be considered the drug of choice. In selected cases (chronic bronchitis, bronchiectasis, and asplenic patients with poor vaccine response), the early use of antibiotics or prolonged use during winter months may decrease the incidence of lower respiratory infections. Use of monthly gamma globulin infusions in total or selective gamma globulin IgG-deficient patients may be beneficial in reducing the incidence of CAP in selected populations.

Community-acquired lower respiratory tract infections. Prevention and cost-control strategies.

The treatment of patients with community-acquired pneumonia can be expensive, particularly if care is hospital-based. Cost control begins with prevention. Current influenza vaccines are about 80 percent protective, but grossly underused. Amantadine and rimantadine are effective chemoprophylactic agents against influenza A, but also underused. Use of pneumococcal vaccine is controversial, but patients who are thought to be at increased risk should be immunized. Management decisions in patients with pneumonia that have major cost implications include the need for hospitalization and choice of diagnostic tests and therapy. The need for hospitalization has not been well studied. In general, young patients with atypical pneumonia are treated at home, whereas older patients with complicating illnesses are admitted to hospitals. Length of hospitalization has decreased in recent years. Diagnostic tests have traditionally emphasized chest roentgenography, Gram staining of the sputum, and sputum culture. Published data suggest that a Gram staining of the sputum can be useful. Sputum cultures are frequently confusing and should be discontinued. Intermittent positive pressure breathing treatments have no value, and chest physiotherapy is unnecessary for most patients.