jueves, 22 de julio de 2010

Use of Anthrax Vaccine in the United States: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009



Use of Anthrax Vaccine in the United States
Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009

Recommendations and Reports
July 23, 2010 / 59(rr06);1-30


Prepared by

Jennifer Gordon Wright, DVM1

Conrad P. Quinn, PhD1

Sean Shadomy, DVM2

Nancy Messonnier, MD1


1Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases

2Bacterial Zoonosis Branch, National Center for Zoonotic, Vectorborne, and Enteric Diseases



Corresponding preparer: Jennifer Gordon Wright, DVM, CDC, 1600 Clifton Road, NE; MS A-38; Atlanta, GA 30333. Telephone: 404-639-4749; Fax: 404-639-2205; E-mail: jgwright@cdc.gov. The material in this report originated in the National Center for Immunization and Respiratory Diseases, Anne Schuchat, MD, Director.

Summary
These recommendations from the Advisory Committee on Immunization Practices (ACIP) update the previous recommendations for anthrax vaccine adsorbed (AVA) (CDC. Use of anthrax vaccine in the United States: Recommendations of the Advisory Committee on Immunization Practices [ACIP]. MMWR 2000;49:1--20; CDC. Use of anthrax vaccine in response to terrorism: supplemental recommendations of the Advisory Committee on Immunization Practices [ACIP]. MMWR 2002;51:1024--6) and reflect the status of anthrax vaccine supplies in the United States. This statement 1) provides updated information on anthrax epidemiology; 2) summarizes the evidence regarding the effectiveness and efficacy, immunogenicity, and safety of AVA; 3) provides recommendations for pre-event and preexposure use of AVA; and 4) provides recommendations for postexposure use of AVA. In certain instances, recommendations that did not change were clarified. No new licensed anthrax vaccines are presented.

Substantial changes to these recommendations include the following: 1) reducing the number of doses required to complete the pre-event and preexposure primary series from 6 doses to 5 doses, 2) recommending intramuscular rather than subcutaneous AVA administration for preexposure use, 3) recommending AVA as a component of postexposure prophylaxis in pregnant women exposed to aerosolized Bacillus anthracis spores, 4) providing guidance regarding preexposure vaccination of emergency and other responder organizations under the direction of an occupational health program, and 5) recommending 60 days of antimicrobial prophylaxis in conjunction with 3 doses of AVA for optimal protection of previously unvaccinated persons after exposure to aerosolized B. anthracis spores.

Introduction
Anthrax is a zoonotic disease caused by the spore-forming bacterium Bacillus anthracis (1,2). The disease most commonly occurs in wild and domestic mammals (e.g., cattle, sheep, goats, camels, antelope, and other herbivores) (3). Anthrax occurs in humans when they are exposed to infected animals or tissue from infected animals or when they are directly exposed to B. anthracis spores (4--6). Depending on the route of exposure, anthrax can occur in three forms: cutaneous, gastrointestinal, or inhalation.

Today, B. anthracis is considered one of the most serious biowarfare or bioterrorism agents because of the ability of the spores to persist in the environment, the ability of the aerosolized spores to readily cause infection via respiratory (inhalation) exposure, and the high mortality of resulting inhalation anthrax (7--9). CDC has classified anthrax as a category A biological warfare agent (10), meaning it has great potential to adversely affect public health. The lethality of aerosolized B. anthracis spores was demonstrated in 1979 when an unintentional release of B. anthracis spores from a military microbiology facility in the former Soviet Union resulted in 64 deaths (11). The cases of anthrax that occurred after B. anthracis spores were distributed through the U.S. mail in 2001 further underscored the potential dangers of this organism as a bioterrorism threat (12--15).

Vaccines against anthrax were first developed as early as 1880 and used in livestock (16). An acellular product for human use was developed in 1954 and used in the first U.S. efficacy study of human anthrax vaccine (17). This product was later modified, resulting in anthrax vaccine adsorbed (AVA) (18), the vaccine currently approved for use in the United States. AVA prepared using B. anthracis V770-NP1-R was first licensed in the United States in 1972 as a 6-dose, subcutaneously (SC) administered priming series with annual boosters for persons in occupations placing them at risk for exposure. AVA also is available as a component of a postexposure prophylaxis (PEP) regimen under an Investigational New Drug (IND) protocol (19) and may be made available under an Emergency Use Authorization (EUA) (20--22).

Methods
In 2000 and 2002, CDC provided recommendations from the Advisory Committee on Immunization Practices (ACIP) for the use of anthrax vaccine for prevention and as a component of PEP (23,24). Because of 1) new safety and immunogenicity data for AVA, 2) a pending licensure change for AVA, 3) the need to incorporate anthrax vaccine recommendations into one document, and 4) new epidemiology data, the ACIP Anthrax Vaccine Work Group convened for the first time for an in-person meeting in October 2007. The work group consisted of 35 members representing the Department of Defense (DoD), the American College of Occupational and Environmental Medicine, the InterAgency Board for Equipment Standardization and Interoperability, the Office of the Biomedical Advanced Research and Development Authority, the National Institutes of Health (NIH), the American Veterinary Medical Association, the American Academy of Pediatrics, the American College of Obstetrics and Gynecology, the National Association of County and City Health Officials, and the Food and Drug Administration (FDA). The work group subsequently held 12 conference calls over 11 months to review and discuss both published and unpublished scientific data related to AVA. Relevant literature was identified through consultations with expert partners and other researchers. These data included safety evaluations, immunogenicity studies, efficacy analyses, vaccine supply information, and contemporary experience with the use of AVA both as a preexposure vaccine and as a component of PEP. Work group members developed recommendation options during their calls. When scientific evidence was lacking, recommendations incorporated expert opinions of the work group members.

In December 2008, FDA approved a dose reduction and route change for AVA administration (25) following submission of a biologics license application (BLA) (26) supplement that was originally submitted in June 2005 by Emergent BioSolutions (Rockville, Maryland). This approval was based on data from the CDC-sponsored Anthrax Vaccine Research Program (AVRP) phase 4 clinical trial (referred to as the AVRP clinical trial in this report).

During the ACIP meeting in February 2008, presentations were made on anthrax epidemiology and transmission, published AVA safety and efficacy data, and unpublished data from the AVRP clinical trial. In June 2008, draft recommendations were presented to ACIP. During the October 2008 meeting, revised recommendations, with the exception of the dose reduction and route change, were presented to ACIP for a vote. In February 2009, ACIP recommended a new, 5-dose pre-event and preexposure priming series administered intramuscularly (IM) (27).

Background
B. anthracis is a facultatively anaerobic, gram-positive, encapsulated, spore-forming, nonmotile rod. The infectious form of B. anthracis that is predominantly found in the environment is the spore, which is approximately 1 µm × 2 µm; anthrax is contracted from these spores, which are highly resistant to heat, cold, drought, UV light, and gamma radiation. B. anthracis has three major virulence factors: an antiphagocytic capsule and two exotoxins, referred to as lethal toxin and edema toxin. These toxins are responsible for the primary clinical manifestations of hemorrhage, edema, necrosis, and death.

Disease is categorized according to the route of human exposure to B. anthracis spores: cutaneous, gastrointestinal, or inhalation. The precise infectious dose of B. anthracis in humans by the various routes is not known; inhalation anthrax can develop in susceptible hosts after exposure to a relatively small number of spores (28,29). Based on data from studies of nonhuman primates, the lethal dose has been estimated to range from 2,500 to 760,000 spores (11,30). The majority of human anthrax cases worldwide are naturally occurring (i.e., not a result of bioterrorism). The case-fatality rate for anthrax ranges from <1% (for cutaneous anthrax treated with appropriate antimicrobial agents) to 86%--89% (during the 1979 outbreak in the former Soviet Union and in the United States during the 20th century, respectively) (6,11,31,32).

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Use of Anthrax Vaccine in the United States: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009

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