Fewer Side Effects In New Anthrax Vaccine Regimen

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Article Date: 01 Oct 2008 - 0:00 PDT

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According to new research published in the October 1 issue of JAMA, changing administration and dosing of an anthrax vaccine gives favorable results and reduces side effects. Specifically, researchers found that fewer doses of intramuscularly injected of an anthrax vaccine results in similar levels of effectiveness and fewer adverse events than the current vaccination regimen.

"Simpler and better tolerated regimens for vaccination with anthrax vaccine adsorbed (AVA) are needed," write the researchers who are from the Centers for Disease Control and Prevention, Atlanta, and the Anthrax Vaccine Research Program Working Group. Currently, the licensed AVA vaccination regimen is injected subcutaneously (below the skin) at 0, 2, and 4 weeks, 6, 12 and 18 months, and annual boosters following. There is not a lot of data that support this vaccination regimen.

The safety and effectiveness of the new vaccine regimen were evaluated with a randomized clinical trial that consisted of 1,005 enrollees. The researchers assessed serological outcomes of alternative schedules and routes of AVA administration. A control group of 169 participants received saline injections, 165 to 170 participants received four injections of AVA subcutaneously (SQ) or intramuscularly (IM) at 0, 2 and 4 weeks and 6 months (4-SQ or 4-IM), and 501 patients received a reduced 3-dose schedule (3-IM).

Results showed that after the first four injections (at month 7), all groups had serum antibody responses that were not less than the licensed regimen. Participants in the 4-IM group were less likely to experience injection site adverse events (AEs) like warmth, tenderness, itching, abnormal redness of the skin, and swelling, than those in the 4-SQ group. Further, the 4-IM group saw a 50% reduction in the odds ratio for ordinal pain immediately after injection compared to the 4-SQ group - a variable ranging from no pain to extreme pain.

"Our data demonstrate that a 3-IM regimen (omission of the week 2 dose) elicits serum antibody responses at month 7 that are noninferior when compared with regimens containing 4 doses of AVA (SQ or IM). Intramuscular administration was associated with a significant reduction in injection site AEs. Changing the injection route from SQ to IM 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," conclude the authors.

Effects of a Reduced Dose Schedule and Intramuscular Administration of Anthrax Vaccine Adsorbed on Immunogenicity and Safety at 7 Months: A Randomized Trial
Nina Marano; Brian D. Plikaytis; Stacey W. Martin; Charles Rose; Vera A. Semenova; Sandra K. Martin; Alison E. Freeman; Han Li; Mark J. Mulligan; Scott D. Parker; Janiine Babcock; Wendy Keitel; Hana El Sahly; Gregory A. Poland; Robert M. Jacobson; Harry L. Keyserling; Stephen D. Soroka; Sarah P. Fox; John L. Stamper; Michael M. McNeil; Bradley A. Perkins; Nancy Messonnier; Conrad P. Quinn; for the Anthrax Vaccine Research Program Working Group
JAMA (2008); 300[13]: pp. 1532-1543..
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Written by: Peter M Crosta
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