How Do Vaccines Work and Are They Dangerous?

How do vaccines work? Are they dangerous?

By Jimmy Rogers (@me)
Contributing Writer, [GAS]

About a week ago, my mother (who is a nurse) asked me, “What can I tell my patients to make them understand why a live virus vaccine isn’t scary just because it’s alive?” I answered her question to the best of my knowledge, but it got me thinking about how little the average person knows in regards to vaccines.

To the layman, a vaccine is essentially some kind of representation of a disease that allows the immune system to get a head start on protecting you. In fact some people probably don’t even know that! While the above is not wrong, I think making an informed decision is always preferable to blindly trusting the magic of science. Read on if you agree!

Who Are We Dealing With?

lymphoma_250The first step in understanding vaccines is understanding the players involved.  On the “them” side are the pathogens, generally bacteria or viruses that cause diseases.  On the “you” side is your immune system, which tries to ward off infections and keep you healthy.  Normally when the adaptive immune system (made up primarily of cells that can recognize very specific parts of pathogens) “sees” a foreign object or organism for the first time, it works not only to clear your body of that invader, but also creates a large number of memory cells that are specifically tuned to react to it.  If you become infected again with that same invader (the recognized piece of the invader is called an “antigen”), the immune system will be able to immediately recognize it and clear it much faster because those special memory cells are already in place.

Keep in mind that this is an enormous oversimplification of the process.  Most pathogens are prevented from even gaining a foothold by your innate immune system, which uses non-specific measure like your skin and mucus membranes.  Only once your innate side has essentially lost ground does your adaptive immune system become activated and being to tune itself to specific antigens.

Intro to Vaccines

Where do vaccines come into all of this?  Well, scientists have determined that the second, faster response to an antigen can be primed by fooling the immune system a little bit.  If it’s flu season, for instance, it’s a good bet that a lot of people will contract a certain kind of influenza.  Vaccine makers can add examples of the strain(s) of influenza they expect to that season’s flu vaccine and distribute it to a large number of people.  The people who get the shot will have a very mild response to the vaccine flu (because the immune system easily defeats it) and their bodies will now be prepared in the event of a “real” infection out in the wild.

Another benefit to the vaccine method is an idea called “herd immunity.”  If you vaccinate 80 percent of a herd of cows against a disease, you will be preventing most of them from becoming infected and consequently spreading the disease.  As an added bonus, the 20 percent without the vaccine are much less likely to run into it either.  This is because many diseases are spread from individual to individual and by breaking the links in the infection chain, the disease will spread much slower in a population.  This works as well as in cows as it does in people!

Types of Vaccines

Types of VaccinesLet’s get into the nitty-gritty for a few minutes.  What exactly is inside this mysterious vaccine?  As I said before, the vaccine serves as an example to your immune system of what a particular invader “looks like.”  What does that really mean?  Well, immune cells have receptors that bind very specifically to certain biological elements like proteins.  When they bind to our cells, they sense “like” or “self” and ignore them.  When they bind to something foreign, they activate the adaptive immune response.  There are several ways for us to artificially replicate this process.

The first and simplest way to trigger a protective response is to give a patient a dose of either a weakened or killed bacterium (or virus).  Weakening, also known as attenuating, can be accomplished by growing the pathogen in either a strange environment, such as an abnormally low temperature, or in a non-human host, such as a rabbit or a guinea pig.  Killing is usually done with either a chemical or a temperature that is lethal to the pathogen.  One downside to the latter approach is that the all-important antigen recognition sites on that pathogen (called “epitopes” by immunologists) can change and misinform the immune system, leading to an ineffective vaccine.

Most of the vaccines you take during your life will fall into the above categories: live attenuated or killed.  Some, though, go about things differently.  Subunit vaccines, for instance, use only the parts of the pathogen most easily recognized by the immune system.  While this may seem like a much smarter idea, these vaccines are not as common because they can be complicated to produce effectively and they expose the immune system to far fewer antigens than whole cells.

One vaccine you may have taken that does not use whole cells is the tetanus vaccine.  The bacterium that causes tetanus, Clostridium tetani, is relatively harmless to humans.  It produces a toxin, though, that can result in lockjaw.  The vaccine uses inactivated forms of the tetanus toxin, instead of the bacteria itself, to help your body recognize and neutralize the functional toxin before it can do any damage.

For more info on the different types of vaccines, I suggest the NIAID/NIH page.

Potential Danger of Vaccines

Those are the primary types of vaccines you will probably encounter today.  There are a number of new strategies being developed, but for the sake of time, I’ll finish up with a word of caution.  Vaccines, by and large, are a very safe technology.  Billions of people have used them for many many years now and there is a great deal of oversight in their creation.  That being said, there are ALWAYS risks with any medicine and vaccines are no exception.

First and foremost, live vaccines can, in rare instances, “revert” into a virulent form of the disease.  The Sabin polio vaccine (a live attenuated vaccine) has been known to do this and is, for that reason, only used in high risk areas.  It is much more effective than the Salk killed virus vaccine, so in some parts of the world the benefits outweigh the risks.

Also, some people have negative reactions to the ingredients in some vaccine.  Whether it’s a high sensitivity to the antigens themselves or an overreaction to the adjuvants (immunization enhancers required for many vaccines to function), there will always be a small number of patients with adverse side effects.  If you want to know more about a specific vaccine, ask for an information sheet from the clinic or hospital detailing the type of vaccine and any prominent risks.  Just don’t expect technical specs like it’s a piece of software.

In the end, you have to weigh your options just like anything else.  The odds are relatively low that you’ll get more than a little sore in the arm from your flu shot.  The FDA (which sets the standard in most of the world for vaccine oversight) keeps a very close eye on new vaccines and requires that any with abnormally high instances of side effects be recalled and reviewed.  As a relatively well educated microbiology student, I feel safe and comfortable taking vaccines to protect me from anything I might be at risk of contracting.

What do you think?  Are you planning to get your flu shot(s)?  Have you already done so?  Any other questions about vaccines?  If so, please post them in the comments and I’ll try to answer your questions.  Also, you can @ me on Twitter!

[Antibody image from The NY Times and MabThera Virtual Press Office | Vaccination image from MSNBC-Health | Header picture: Flickr (CC)]





26 Responses to How Do Vaccines Work and Are They Dangerous?

  1. To explain it very very pixibook-ish.

    It’s like taken the flag of your enemy and run it through the base having every one shoot at it, making them (your men at arms aka immune system) alert, so next time they see that “flag” (even though it’s just a small part of the whole enemy soldier) your men at arms are ready, buffed up, and have the image of the enemy clear and present in mind ;)

  2. To explain it very very pixibook-ish.

    It’s like taken the flag of your enemy and run it through the base having every one shoot at it, making them (your men at arms aka immune system) alert, so next time they see that “flag” (even though it’s just a small part of the whole enemy soldier) your men at arms are ready, buffed up, and have the image of the enemy clear and present in mind ;)

  3. Yes, I have a question: as a type 1 diabetic, should I take the "live" Swine Flu vaccine, or should I take the "dead" Swine Flu vaccine? I understand from you great article that the live one is better to take, but my immune system is a bit depressed because of the diabetes, so I am not sure it is a good choice for me.

    Thank you very much. I hope your further studies go well.

    • Hey Tim,

      I would like to point out that this isn't really a "medical advice" blog. I don't know too much about how vaccines effect the immunocompromised, other than sometimes vaccines are less effective. I would absolutely talk to your doctor and see what they recommend before doing anything.

      Thanks for reading!

  4. Yes, I have a question: as a type 1 diabetic, should I take the “live” Swine Flu vaccine, or should I take the “dead” Swine Flu vaccine? I understand from you great article that the live one is better to take, but my immune system is a bit depressed because of the diabetes, so I am not sure it is a good choice for me.

    Thank you very much. I hope your further studies go well.

  5. Yes, I have a question: as a type 1 diabetic, should I take the “live” Swine Flu vaccine, or should I take the “dead” Swine Flu vaccine? I understand from you great article that the live one is better to take, but my immune system is a bit depressed because of the diabetes, so I am not sure it is a good choice for me.

    Thank you very much. I hope your further studies go well.

    • Hey Tim,

      I would like to point out that this isn’t really a “medical advice” blog. I don’t know too much about how vaccines effect the immunocompromised, other than sometimes vaccines are less effective. I would absolutely talk to your doctor and see what they recommend before doing anything.

      Thanks for reading!

  6. Vaccines are not dangerous because of the viruses inside of them. They are dangerous because of the methylmercury, squaline, and the formaldehyde in them. You're article has completely missed the risk involved. If it wasn't for these three ingredients, then vaccinations would be perfectly safe. As it stands now, these three ingredients can cause all sorts of nerological disorders. Namely in children. If you child has austism, it's probably because you had him stuck.

    • While I agree that the article should have addressed these issues, as these are the sorts of things that many anti-vaccination advocates are concerned about, it is also extremely insensitive to attempt to make parents of autistic children feel somehow personally responsible with statements such as "If you child has austism, it’s probably because you had him stuck.", especially when there is absolutely no scientific evidence to suggest that vaccines cause autism.

      Vaccines used to contain the preservative thimerosal, the active ingredient is ethylmercury (NOT methylmercury), an organic version of mercury that is quickly expelled from the body. Ethylmercury is not the same thing as mercury or methylmercury, and cannot cause heavy metal poisoning as mercury can. Even if you could somehow get mercury poisoning from a vaccine containing ethylmercury, ethylmercury was removed from all vaccines in 1997 as a precaution, and to encourage anti-vaccination advocates that the ingredient they were so worried about is no longer contained in any vaccines. If there was a true causal link between ethylmercury in vaccines and autism, you would think its removal would dramatically decrease the rate of autism diagnosis over the years, and yet, the incidence of autism continues to rise. Regardless, 13 years later, people are still carrying on about mercury in vaccines!

      Squaline is a naturally ocurring substance that is produced by our own livers and is circulating through your bloodstream right now. Using data from 64 medical trials, a meta-analysis by Pellegrini, Nicolay, Lindert, Groth, and Della Cioppa (2009) revealed that the use of squaline in vaccines not only is totally safe, but also is associated with lower rates of chronic desease.

      As for formaldehyde? It too is a naturally-ocurring substance in all living things. In fact, the concentration of naturally-ocurring formaldehyde in our bodies (2 ppm) is higher than the concentrationlevels of formaldehyde in any vaccine. Our bodies have evolved a mechanism to keep our levels of formaldehyde in check so that they do not reach a level that is toxic to cells. So if anything, an injection is slightly diluting the level of formaldehyde in our bodies.

      And what of the man who started it all? Dr Andrew Wakefield, the researcher at the center of the original Lancet paper in 1998 that outlined the "link" between the childhood MMR vaccine and autism, has been found to be "dishonest", "irresponsible", and guilty of putting children through lengthy and unnecessary tests and "serious professional misconduct" by the UK General Medical Council. As a result, his medical license has been revoked, and The Lancet has issues a full retraction of the paper stating "It has become clear that several elements of the 1998 paper by Wakefield et al. are incorrect. … Therefore we fully retract this paper from the published record."

      What we know about autism is that in 90% of cases, there is a genetic contribution. It is primarily a genetic, rather than an environmental disorder. Other than the presence of thalidomide during the first 8 weeks of gestation, no rigorous sciuentific research has ever supported that any specific environmental factors including vaccines, food allergies, and mercury poisoning contribute in any way to autism.

      • Wow, great argument and defense of vaccine additives and preservatives. It's still not a clear cut issue, but there is way too much misinformation out there!

      • In regards to Andrew Wakefield, there's an interview with him where he defends himself pretty convincingly. And the results of his 1998 study have been replicated 28 times around the world. It's possible the establishment didn't like their source of income being threatened so they chose to attack and discredit him. I'm not a big advocate of conspiracy *theories*, but when I see actual evidence of it, it's hard to deny. Here's the interview: http://articles.mercola.com/sites/articles/archiv

  7. Vaccines are not dangerous because of the viruses inside of them. They are dangerous because of the methylmercury, squaline, and the formaldehyde in them. You’re article has completely missed the risk involved. If it wasn’t for these three ingredients, then vaccinations would be perfectly safe. As it stands now, these three ingredients can cause all sorts of nerological disorders. Namely in children. If you child has austism, it’s probably because you had him stuck.

    • While I agree that the article should have addressed these issues, as these are the sorts of things that many anti-vaccination advocates are concerned about, it is also extremely insensitive to attempt to make parents of autistic children feel somehow personally responsible with statements such as “If you child has austism, it’s probably because you had him stuck.”, especially when there is absolutely no scientific evidence to suggest that vaccines cause autism.

      Vaccines used to contain the preservative thimerosal, the active ingredient is ethylmercury (NOT methylmercury), an organic version of mercury that is quickly expelled from the body. Ethylmercury is not the same thing as mercury or methylmercury, and cannot cause heavy metal poisoning as mercury can. Even if you could somehow get mercury poisoning from a vaccine containing ethylmercury, ethylmercury was removed from all vaccines in 1997 as a precaution, and to encourage anti-vaccination advocates that the ingredient they were so worried about is no longer contained in any vaccines. If there was a true causal link between ethylmercury in vaccines and autism, you would think its removal would dramatically decrease the rate of autism diagnosis over the years, and yet, the incidence of autism continues to rise. Regardless, 13 years later, people are still carrying on about mercury in vaccines!

      Squaline is a naturally ocurring substance that is produced by our own livers and is circulating through your bloodstream right now. Using data from 64 medical trials, a meta-analysis by Pellegrini, Nicolay, Lindert, Groth, and Della Cioppa (2009) revealed that the use of squaline in vaccines not only is totally safe, but also is associated with lower rates of chronic desease.

      As for formaldehyde? It too is a naturally-ocurring substance in all living things. In fact, the concentration of naturally-ocurring formaldehyde in our bodies (2 ppm) is higher than the concentrationlevels of formaldehyde in any vaccine. Our bodies have evolved a mechanism to keep our levels of formaldehyde in check so that they do not reach a level that is toxic to cells. So if anything, an injection is slightly diluting the level of formaldehyde in our bodies.

      And what of the man who started it all? Dr Andrew Wakefield, the researcher at the center of the original Lancet paper in 1998 that outlined the “link” between the childhood MMR vaccine and autism, has been found to be “dishonest”, “irresponsible”, and guilty of putting children through lengthy and unnecessary tests and “serious professional misconduct” by the UK General Medical Council. As a result, his medical license has been revoked, and The Lancet has issues a full retraction of the paper stating “It has become clear that several elements of the 1998 paper by Wakefield et al. are incorrect. … Therefore we fully retract this paper from the published record.”

      What we know about autism is that in 90% of cases, there is a genetic contribution. It is primarily a genetic, rather than an environmental disorder. Other than the presence of thalidomide during the first 8 weeks of gestation, no rigorous sciuentific research has ever supported that any specific environmental factors including vaccines, food allergies, and mercury poisoning contribute in any way to autism.

      • Wow, great argument and defense of vaccine additives and preservatives. It’s still not a clear cut issue, but there is way too much misinformation out there!

        • On a more cautionary (and scientifically validated) note, the one thing that people really do need to be aware of, is the culture medium used in growing the vaccine. In many cases these vaccines are cultivated in an egg medium, which can trigger an allergic reaction in those people known to suffer with egg allergies. Always ask what the culture medium is, before taking the vaccine, just to check.

        • My son has an allergy to eggs, and I asked his doctors about eggs being in the vaccine. If an individual is not deathly allergic to eggs, then a little discomfort is better than getting a potentially deadly disease.

  8. Just to satisfy my curiosity, what are your thoughts on the efficacy of human vaccines? I'm a veterinarian and while there are many vaccines that we use that are very important in animals (rabies being the classic example), there are many more that have shown very little efficacy and yet still been certified by the FDA. Many of these are pushed heavily for a few years and then later withdrawn when veterinarians and producers realize they have little effect. I'm sure that efficacy has been demonstrated for human vaccines with long track records but what about those that are relatively new and yet still touted whenever I walk into my pharmacy (specific examples slip my mind at the moment)?

  9. When weighing risks versus benefits it is also important to note that vaccines only target a tiny percentage of the strains of a tiny percentage of the illnesses in existence, and not even the most dangerous ones. When considered against the potential risks, the benefits do seem incredibly minimal.

  10. wow. moderated! truth suppression! well at least YOU read it. even if you lack the court age to let my post stand, I'd be curious to se your thoughts on what I said as a generic comment of your own. You can make it sound like "to those that believe…" I gave you a fake email because I didn't want to be on any email list if that's your reason for moderation.

    • Not really, I saw the name under the "name" field, and I assumed that the comment was spam. I get so many comments on this site, that if I read everything, I'd be a this a few hours every day. So if it vaguely looks like spam, I nuke it. Sorry about that. Next time you want to comment, don't use a name that looks like it comes from a spam bot :)