Such as when you get measles you don’t get them again.
According to my Medical Micro textbook, “Immunity appears to exist, but is poorly understood.” Whatever that means.
Probably means that, since it’s not that common to get it even once, getting it twice is really unlikely. So they’re not sure if folks who get it but don’t get it again stay well because they’re immune or because they just aren’t exposed twice.
Also, it’s probably hard to determine how long immunity lasts if there isn’t a big enough sample to study.
So why isn’t there an Anthrax vaccine?
There is a vaccine. Only veterinarians took it until recently when the DoD decided to give it to military personnel. It’s a series of five shots, spaced several weeks or months apart. Some people have questioned the efficacy of the vaccine against “weapons-grade” anthrax. Anthrax developed for use as a biological weapon is, well, it may not be a mutant strain, but I’ve heard that’s it’s different than your run-of-the-mill anthrax.
The Anthrax vaccine web page:
http://www.anthraxvaccine.org/
This link mentions “weapons-grade” anthrax:
http://www.washingtonpost.com/wp-dyn/articles/A11819-2001Oct17.html
What about one form. If one gets cutaneous(sp?) Anthrax and recovers does that protect you form ihahlation form?
I don’t know the specifics of the anthrax vaccine, but in general for any vaccine to be effective, there must be a form of natural immunity for the vaccine to exploit. The vaccine provides an appropriate, and one hopes a non-pathogenic, antigenic stimulus that prompts the body to produce either cytotoxic cell-mediated immunity or antigen neutralizing antibodies in the event that the host encounters the actual pathogen.
BCG vaccine for TB is an example of a vaccine that is designed to prompt a cell-mediated response to MTB. HepB vaccine is designed to prompt an antibody response to HBV.
I’m not sure how the anthrax vaccine is supposed to work, but it would have to use one of these mechanisms.
There are other strategies for vaccines. Rabies vaccine induces antibodies against the Rabies virus. It is unique in that it may be given after a rabies exposure, due to the usually long latency between a rabid animal bite and the neuronal transport of the Rabies virus from the wound to the CNS.
“Passive” immunity may be conferred by injecting antibodies (usually in the form of pooled immune serum) into the host. The classic example is Hepatitis B Immune Globulin for post-exposure treatment of Hep B.
If there’s a vaccine, why can’t it be made available to all in the way that the polio vaccine is part of everyone’s routine medical maintenance in life? I can probably answer this myself intuitively (expensive, too difficult to produce in large quantities, simply not necessary given that anthrax is hardly a problem on an epidemic level (at least not at this time)etc.) but I’m curious as to the actual real reason(s).
Well, aside from there being some cost to an anthrax vaccine, it requires one intial shot then 3 boosters given one year apart. So it’s not a matter of one stab in the arm and you’re done. There’s a logistical problem to getting people to come back for another shot four years running.
Thus, it’s been used by vet, agricultural workers who, being at higher risk, have incentive to show up for their boosters, and the military, where you can be ordered to do things you would otherwise forget and/or not bother with.
Apparently, there have also been some nasty side effects to the vaccine in some cases. So you have to weigh the likelihood of bad reactions to the vaccine versus the odds of catching and suffering harm from the disease.
This is why the smallpox vaccine was discontinued - After 1979 or so there was no smallpox left to catch (outside of secure laboratories) but about 1 in a million folks receiving the vaccine die from it, and about 1 in 300,000 have a reaction serious enough to require further medical treatment.
I hear that the incidence of side effects from the anthrax vaccine is higher, but have no exact statistics on it. No point in vaccinating 300 million people in the US, expecting 300 deaths and nearly 1000 additional serious reactions if only one or two folks catch a disease in a year and a person dies only once in a decade. Likewise, even though rabies is an extremely deadly disease we don’t vaccinate the whole population against it because the odds of catching it are so low for most people (vets, animal control officers, and sometimes spelunkers are exceptions).
The anthrax vaccine consists of a mixture of three proteins (protective antigen, edema factor, and lethal factor-see below) secreted by the bug as it grows in culture. The mixture is purified and adsored onto a particulate adjvant (immunostimulatory compound). The protective response is mediated by antibodies which target the proteins in the vaccine.
I havent’t read anything about naturally-occurring anthrax immunity, but I’d bet anything, anything I tell ya’, that if you recover from (let’s say) cutaneous anthrax, you’re immune for life, perhaps against all three forms of anthrax disease.
Why do I believe there’s alot going for anthrax immunity?
First some basic anthrax biology. The bacterium kills infected hosts by the elaboration of a toxin. From Harrison’s Online
Non-toxin producing strains are not harmful. And the three proteins that comprise the toxin are those in the vaccine. Therefore, no toxin, no disease and if one has anti-toxin antibodies, no disease. So if one wished to say that natural infection does not confer immunity, they’d need to explain why anti-toxin antibodies would fail to develop during a response to anthrax infection or why that original response would be ineffective upon re-exposure.
I’d find it difficult to imagine that anti-toxin antibodies fail to develop upon natural infection. They are secreted proteins. That means that they’ll be accessible and of a chemical form (protein) that is best recognized and responded to by the adaptive immune system. I’ve seen in the press that post-exposure antibody titers have been measured in some of the Capitol Hill workers as well (although I don’t know if they are looking at anti-toxin antibody levels). In addition, natural infection commonly results in higher levels of immunity than vaccination. Therefore, I predict high levels of anti-toxin antibodies in an anthrax convalescent
Now turing to the question of whether those antibodies will be of any use, consider the case of influenza. We are all succeptible to the flu each winter, irrespective of past exposure. Why? Because each year the flu appears in a slightly different form. The antibodies you made last year no longer bind to the new strain, making you immunologically naive with respect to the new strain. Fortunately, the secreted toxin of B. anthracis demonstrates no such variation.
In summary, I predict protective immunity will result from previous anthrax exposure because:
[ul]
[li] Antibody responses to the Anthrax toxin are protective[/li][li] The toxin is a secreted protein, a format recognized well by the adaptive immune system[/li] Toxin variation has not been observed[/ul]
I’ve seen the building where anthrax vaccine is produced in Michigan. There are many diseases that are preventable via immunization, but the shots are not routinely given. With rare diseases, it’s not cost effective to immunize the entire population and there would be more adverse events from the immunizations (or blamed on them) than cases of disease prevented. In those cases, immunization is only offered to those possible exposed when there is an outbreak.
Jill
I thought vaccines are for viruses while anthrax is a bacteria.
[[I thought vaccines are for viruses while anthrax is a bacteria.]]
Uh…
No. There are vaccines for some of each. And some for which no vaccine is available… Viruses like HIV, Hepatitis C, and a gazillion others.
Common vaccines
Bacterial Vaccines Viral Vaccines
Diphteria Measles
Pertussis Rubella
Tetanus Mumps
Haemophilus HepB
S. pneumoniae HepA
Anthrax Polio