TUESDAY, Sept. 30 (HealthDay News) -- A three-dose intramuscular (3-IM) regimen of anthrax vaccine adsorbed (AVA) achieves a similar serological response compared to a four-dose intramuscular (4-IM) or subcutaneous (4-SQ) regimen, and fewer injection site adverse effects are seen with IM administration, according to a report in the Oct. 1 issue of the Journal of the American Medical Association .
Nina Marano, of the U.S. Centers for Disease Control and Prevention in Atlanta, and colleagues examined results from a randomized controlled trial comparing serologic response and injection site adverse events between a 3-IM AVA schedule and both the 4-IM and 4-SQ AVA schedules. Main outcome measures were non-inferiority at week 8 and month 7 based on antiprotective antigen IgG geometric mean concentration, geometric mean titer, and proportion of responders with a fourfold rise in titer, and proportion of injection site and systemic adverse events.
Among the 1,005 participants at 8 weeks, the 4-IM regimen was non-inferior to the 4-SQ regimen for all outcomes, while the 3-IM regimen was inferior to both four-dose regimens for the proportion of responders achieving a fourfold rise in titer, the researchers report. At 7 months, all regimens were non-inferior for the main outcome measures. Injection site adverse events were significantly lower among the intramuscular compared to the subcutaneous regimen.
"Our data demonstrate that a 3-IM regimen (omission of the week 2 dose) elicits serum antibody responses at month 7 that are non-inferior when compared with regimens containing four doses of AVA (subcutaneous or intramuscular)," the authors conclude. "Changing the injection route from subcutaneous to intramuscular may increase vaccine acceptability. Reducing the number of doses in the AVA regimen would have the added benefit of increasing the number of doses available for prophylactic use."
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