What is anthrax?
Anthrax is a severe bacterial disease that primarily affects warm blooded animals, especially livestock. Humans can be infected as well. The disease is caused by the bacterium Bacillus anthracis, which produces spores that can remain dormant for years in soil and on animal products, such as hides, wool, hair, or bones.(1)
How is anthrax contracted?
Animals get the disease by eating infected grass or carcasses, drinking infected water, or inhaling infected dust. They die suddenly with little or no symptoms.(2) People contract anthrax in one of three ways: 1) by coming into contact with the bacterium, or infected animals or animal products, 2) by inhaling airborne particles, or 3) by eating undercooked meat from diseased livestock.(3)
How common is the disease?
Anthrax is rare; when it does occur, it is almost always an occupational hazard, contracted by those who sort wool or handle animal hides -- farmers, butchers, and veterinarians. The disease is most often found in agricultural regions of South and Central America, eastern Europe, Asia, Africa, and the Middle East.(4) In the United States, during the early 1900s there were about 200 cases per year of the less threatening form in which the bacterium infects the skin.(5) In 1957, nine employees of a goat hair processing company became ill after handling a contaminated shipment from overseas.(6) In the 1970s, other cases occurred when contaminated goatskin drumheads were imported as souvenirs.(7) From 1900 to 1976, only 18 cases of the inhaled version were reported in the U.S.(8) However, in 2001 anthrax was mailed to several media outlets and federal offices in the U.S. exposing numerous people to the disease.(9)
What are the symptoms of anthrax?
Symptoms usually appear within one week of exposure but vary depending upon how the disease was contracted:
1. Cutaneous anthrax is the most common, and mildest, form of the disease. This occurs through skin contact -- when the bacteria enter a cut or wound. At first, an itchy raised area like an insect bite appears. Within one to two days, inflammation occurs and a blister forms around a black center of dying tissue. Other symptoms include shivering and chills. If bacteria spread to the nearest lymph gland, the disease can cause a form of blood poisoning that is fatal.
2. Inhalation or pulmonary anthrax occurs by inhaling the bacteria or bacterial spores. The disease begins with cold or flu-like symptoms -- fever, fatigue, and headache—then progresses to bronchitis, pneumonia, and a state of shock. This rare form of anthrax is usually fatal.
3. Intestinal anthrax is caused by eating meat from an infected animal. The first signs are nausea and vomiting, loss of appetite, fever, and abdominal pain. It progresses to inflammation and ulcers of the stomach and intestines, vomiting of blood, and bloody diarrhea. This form of anthrax is also rare and often fatal.(10)
Is there a treatment for anthrax?
If caught early, anthrax is curable by administering high doses of penicillin.(11) Several antibiotics are effective against anthrax when it occurs naturally. Ciprofloxacin (Cipro) and doxycycline (Doxy) have been licensed by the FDA for use against all forms of the disease.(12) However, moderate to severe side effects are possible. For example, adverse reactions to Ciprofloxacin include nausea, diarrhea, vomiting, headache, stomach pain, skin rashes, mental confusion, tremors, seizures, hallucinations, and torn tendons. In one study, 16.5 percent of all Cipro recipients had adverse reactions. The drug had to be discontinued in 3.5 percent of the patients.(13) In a more recent study, 19 percent of all postal workers using "anti-microbial prophylaxis" for anthrax reported adverse reactions. Most were using Cipro. Eighty-two of the 3,863 people in the study group (2 percent) sought medical attention for symptoms of anaphylaxis, a potentially life-threatening allergic reaction. Eight percent of the Cipro recipients quit the medication.(14,15) Doxycycline is thought to be less reactive, but has been linked to nausea, vomiting, headache, chest pain, facial swelling, throat and tongue inflammation, genital and rectal itching, skin peeling, and hives.(16,17)
Cutaneous anthrax may be cured following a single dose of penicillin though longer treatment is suggested. Victims of inhalation anthrax must take high doses of antibiotics for 60 days, starting right after exposure. Some doctors use other regimens as well.(18)
Anthrax is not considered contagious. There are no reports of the disease spreading from human to human. Thus, communicability is not likely when managing or visiting ill patients.(19) However, the prognosis for untreated anthrax is poor. About 20 percent of all unattended cutaneous cases will end in death. Most treated patients will recover.(20) All patients with inhalation anthrax will die if left untreated.(21) Only 10 percent will survive if treatment is postponed until symptoms appear and the spores have begun to release toxins.(22) Intestinal anthrax is fatal in about half the cases.(23)
Does an anthrax vaccine exist?
In 1863, anthrax became the first disease for which a causative agent -- Bacillus anthracis -- was isolated.(24) In 1881, Louis Pasteur developed an anthrax vaccine for animals.(25) In 1935, a more virulent, live anthrax vaccine was produced. However, goats, llamas, and other animals often died following vaccination.(26) By 1940, the Soviet Union developed the first anthrax vaccine for human use.(27) The United States and Great Britain produced human anthrax vaccines during the 1950s.(28) The currently available U.S. vaccine was formulated in the 1960s and licensed by the FDA in 1970, two years before efficacy data (scientific proof that it works) were required.(29,30)
How safe and effective is the anthrax vaccine?
In 1954, researchers injected 25 rabbits with an anthrax vaccine. They were intentionally killed 23 days later. Autopsies revealed nothing unusual.(31) These same researchers studied short-term side-effects to anthrax injections in human subjects. They found a number of local and systemic reactions, including swelling at the injection site (up to 10cm in diameter), muscle aches, headaches, and mild-to-moderate malaise. Reaction rates increased with subsequent shots.(32)
In 1956, Lancet published a study that investigated the anthrax vaccine in both monkeys and humans. Some vaccine reactions were reported, but definitive conclusions could not be drawn because long-term follow-up of the study subjects was not conducted.(33)
In 1962, the American Journal of Public Health published the only randomized clinical study (Brachman, et al.) of a "protective-antigen anthrax vaccine."(34) Employees at four factories where anthrax-tainted goat hair was handled, were vaccinated. Although participants were only monitored for ill effects that occurred within two days of each shot, and reaction rates within this restricted time frame were not recorded, some common side effects were noted, including "a ring of erythema" (greater than 5cm in diameter), nodules at the injection site (lasting several weeks), edema extending from the deltoid to the mid-forearm or wrist, and malaise.(35)
During the four year study period, there were 26 cases of anthrax (21 were cutaneous; 5 were inhalation). Three of these cases occurred in either partially or fully vaccinated recipients. The authors of the study concluded that the vaccine was 92.5 percent effective.(36) However, statistical analysis of the data was confounded by arithmetic errors.(37) According to Dr. Meryl Nass, a recognized expert on anthrax and biological warfare, "the actual percent efficacy cannot be calculated due to the small number of cases...five inhalation cases do not permit any conclusion about vaccine efficacy with regard to inhaled organisms."(38) Also, according to a March 2000 investigative report issued by the Institute of Medicine (IOM), vaccine research was terminated at one of the four factories (the largest of the study sites) after the initial series of three injections.(39) According to one nurse, there were "a large number of systemic reactions."(40) But data from this site was omitted from the study results.(41) The IOM report also noted that 81 subjects withdrew from the vaccine trials (at the other three factories) before completing the series of shots, yet data from these individuals was omitted from the study results as well.(42) Furthermore, the study fails to note whether the investigators were "blinded" or had knowledge (study bias) regarding who received the active vaccine or placebo.(43)
In 1962, and again in 1971, 76 employees at Fort Detrick, Maryland were tested to investigate the potential effects of intensive vaccination. Seventy-two of the 76 subjects had previously received the anthrax vaccine (plus other vaccinations). Although no clinical sequelae attributable to intense long-term immunization could be identified, there was evidence of a chronic inflammatory response, as shown by test abnormalities: elevated levels of hexosamine, an acute-phase reactant, and polyclonal elevations of gamma globulins.(44,45) However, no definitive conclusions can be drawn from these studies due to several shortcomings. According to the IOM report, "There was no comparison cohort and no random sampling of the employees. Therefore, the results may not apply to a broader population.' Also, employees who left the study were excluded from the results.(46)
From 1986 to 1995, several studies tested the efficacy of the U.S. human anthrax vaccine on guinea pigs and mice. After the animals were vaccinated (typically with three shots, 2 to 3 weeks apart), they were exposed to several different strains of anthrax. Survival rates for vaccinated guinea pigs ranged from 0 percent to 100 percent.(47-54) Survival rates for vaccinated mice ranged from 0 percent to 10 percent.(55-57)
Several researchers also investigated the protective efficacy of a Russian anthrax vaccine, an English anthrax vaccine, a more virulent, live anthrax vaccine (Sterne), and experimental anthrax vaccines with the addition of novel adjuvants (antibody boosters). Most of these studies were conducted on guinea pigs and mice. The results were similar to those obtained from the U.S. vaccine.(58-61)
In 1993, the Journal of Infectious Diseases published a study in which monkeys were administered an anthrax vaccine shortly after being exposed to the disease. Survival rates were no better than in unvaccinated controls.(62) However, in 1996 U.S. army researchers published the results of a new study in which 25 adult rhesus monkeys received two injections of the human anthrax vaccine (two weeks apart). The monkeys were then exposed to the aerosolized spores of the Ames strain of anthrax at 8 weeks, 38 weeks, or 100 weeks.
All of the vaccinated monkeys survived challenge at either 8 weeks or 38 weeks, and seven of eight monkeys survived challenge at 100 weeks.(63) Although the data in this study suggests that the U.S. human anthrax vaccine may protect adult rhesus monkeys against inhalation anthrax for up to two years, it is important to note that they were only exposed to a single strain of the disease. Researchers are currently aware of more than 1300 strains of anthrax.(64) The authors of this study also note that "immune mechanisms against inhalation anthrax may vary in different animal species." Thus, "these findings suggest...that the ability of the licensed human anthrax vaccine to stimulate cell-mediated immunity may be greater in some species than others."(65) Earlier studies using guinea pigs and mice already demonstrated this.(66) Animals also differ from humans in their immunological responses. No one knows how animal studies of vaccine efficacy can be extrapolated to people. In fact, the scientists who conducted the study admit: "There is currently no known surrogate marker or in vitro correlate of immunity that allows direct comparison of immunity in humans to that in monkeys."(67)
In 1998, U.S. army researchers published another study in which rhesus monkeys were exposed to inhalation anthrax six weeks after being vaccinated with either the U.S. human anthrax vaccine or with experimental anthrax vaccines. The data showed that one dose of each vaccine provided "significant protection."(68) However, the authors of the study also noted that "results of recent studies show that anthrax vaccines vary in their efficacy among different species."(69) And like the earlier primate study, the monkeys were only exposed to a single strain of anthrax. Researchers did not test their vaccines against any of the other hundreds of strains circulating across the globe.
Another study conducted by the DoD in 1998 did test the U.S. human anthrax vaccine against more than 20 different strains from around the world. Guinea pigs were vaccinated prior to being exposed to each strain. Fourteen of the strains killed at least 75 percent of the vaccinated guinea pigs. Nine of the strains killed at least 85 percent of the rodents. Survival rates were even worse for strains found in Zimbabwe, Namibia, and France.(70)
MDPH-PA: The human anthrax vaccine manufactured in the United States is called MDPH-PA (protective antigen) or MDPH-AVA (anthrax vaccine absorbed). It was produced until February 1998 by the Michigan Department of Public Health under contract with the Department of Defense (DoD). The business was sold in September 1998 and renamed Bioport.(71)
MDPH has several drawbacks. The only human field trial used to justify licensing the vaccine was conducted in the late 1950s, and there were not enough cases of the disease to draw valid conclusions about vaccine efficacy.(72) No controlled clinical trials in humans were ever conducted, and there are no peer-reviewed published studies warranting its safety.(73,74) The vaccine was licensed for occupational use -- mainly for veterinarians and other persons "engaged in diagnostic or investigational activities" -- not as a prophylactic against inhalation anthrax.(75) Furthermore, the vaccine formulation has been changed, and the current vaccine contains approximately five times more PA (bacterial matter) than the earlier vaccine.(76)
MDPH has been criticized for other reasons as well. Potency varies from lot to lot.(77) Full coverage requires six injections over a period of 18 months, plus annual booster shots. It is not licensed for children, no one knows the effect on pregnant women or reproductive capacity, and it contains several potentially toxic substances, including aluminum hydroxide, benzethonium chloride, and formaldehyde.(78) According to anthrax expert Dr. Meryl Nass, about 20 percent of those vaccinated develop chronic medical problems. In addition, "It's not highly effective...a number of people who were vaccinated subsequently developed anthrax."(79)