Vaccines (long)

I was going to write this as a response in the comments to my last post, but then it just got too long, so now it's its own post. (Ooh, look at that command of the English language! Two variations of the letters i-t-s, each used correctly, in sequence!)

PCJ writes:
I have to admit that looking at the vaccine schedule, and looking at my tiny, tiny (well, less tiny every day) baby, makes me nervous.

It sometimes feels so counterintuitive, [admittedly as a result of living in a society pretty much free of rampant infectious disease] to load up an infant who seems perfect as she is with chemicals I don't know a lot about. So I honestly can understand how this anti-vax movement is growing. I feel like vaccinating is the right decision, but I would be lying if I said that it was a no brainer, or that I don't occasionally have moments where I get scared and think, "I wonder if 50 years from now we will learn that there are problems caused by vaccinating so much and so early in infancy."

PCJ also expresses concern that she could never find good resources for telling her what the supposed controversies were and how/why they had been refuted. As for that last part, I'm happy to pull some references for you and point you in the right direction. If you have access to a college library system, it makes things easier (the local community college may even have access to medical search engines like PubMed? I'll put together a list of good places to look next week.)

Now, for the first part. First, let’s have an immunology lesson. Antibodies are protein molecules that your body makes that have specific recognition sites for antigens. An antigen is any foreign substance, be it a bacterium or peanut, that your body recognizes as foreign (if you have an autoimmune disease, it means you have abnormal antibodies that recognize your own cells as foreign). You also have a pretty strong barrier system before your antibodies need to swing into action: your skin, nose hair, and snot are all designed to keep foreign objects out. If, however, something gets through, your antibodies will most likely be called into action (OK, there’s another part to the immune system, too, but I’m trying not to write a book here).

You are, at birth, already equipped with all of the antibodies you will ever have. What’s more, you are born with antibodies against every single antigen you will ever encounter, before you encounter it. In fact, you have antibodies against substances that do not even exist on Earth today. If, 20 years from now, someone created a new bacterial species, or aliens landed on the planet and sneezed on us, we – at this very moment – already posses the antibodies that match up to those bacteria and the alien snot. (If you would like an explanation of how/why this happens, just ask.) Therefore, the idea that infants do not have immune systems as strong as those of older children/adults is a misconception. In fact, if you think about it, even if mom doesn’t have something nasty like herpes or syphilis, the “birth canal,” as it is euphemistically called, is still pretty dirty and nasty and germ-filled, and Baby has to have the ability take care of those exposures right away. So that’s how I explain away the idea that it would be better to wait until a child is older to begin vaccinating – aside from the fact that some of those vaccines are for diseases that only pose a risk to infants. More below.

Now, let’s consider the idea that infants get “so many” vaccinations. Here is the CDC schedule of recommended vaccines for infants and children. Take a look at the two-month pediatrician visit. Your average two-month-old who is receiving his or her second dose of Hep B at the two-month visit will receive 6 shots, one of which actually contains 3 vaccines. So that’s 8 immunizations. Eight sounds like a lot compared to none or one – that’s a lot of “stress” on the baby’s immune system, right? Wrong. Remember that everything around you is an antigen. Your body has to “cope” with the “stress” of being bombarded with millions of molecules each day: viruses, bacteria, parasites, fungi, dirt, dust, cat dander, bed bugs… the list is endless. Even someone else’s dead skin cells floating around the air are antigens. Your body – and your baby’s – are able to handle those, so eight more exposures won’t hurt. I promise. Besides which, if any of those eight diseases were as prevalent today as they were 50 years ago, it’s just as likely that your baby would be exposed to all of them at the same time and still make it out OK. So there’s no “stress” involved with exposing a baby to eight vaccines/antigens at once. (There is, however, a very real problem with giving a baby six injections, which is pain. That’s why some vaccines are given in one preparation, like diphtheria, tetanus, and pertussis (DTaP), or the MMR (measles, mumps, rubella), or the new ProQuad (MMR plus varicella). When people do studies, there is a significant health care cost decrease and health effect of combining vaccines into fewer injections.)

Now let’s consider the typical course of an infection and why vaccines work. An immune defense is normally mounted in the following way: an antigen makes its way into your system, past your barrier defenses (skin, nose hair, snot, etc). It floats around, and lots of antibody-producing cells come into contact with it. It will probably infect its target cells first, which is what will make you clinically sick. Eventually, one of those antibody cells that bumps into the antigen sees that it's a match, and starts churning out clones of its antibody. Some of the antibodies help your body fight the current infection, and others hang around for life, primed and waiting for a second exposure to the antigen so they're ready to fight it. When you get exposed to the antigen again, those antibodies are ready, so there’s no lag time for an immune response to be mounted. So that's why you only get chicken pox once. The first time, you get sick. The second, third, fourth, and hundredth times you get exposed, your antibodies attack and neutralize the virus before it can get the disease process underway. The “natural” way to gain immunity, then, is to be exposed to antigens, and that’s how humans lived for many, many years. If you succumbed to the infection, well, too bad; if you survived measles, mumps, chicken pox, smallpox, diphtheria, tetanus, pertussis, meningitis, pneumonia, polio, and rotavirus, then congratulations, you got to live and reproduce.

The miracle of modern medicine (and indeed, the CDC has called it one of the 10 greatest public health achievements of the 20^th century) is that we are able to mimic having an initial exposure to these antigens without the morbidity and mortality of the associated clinical illnesses. You can give everyone smallpox and congratulate those who survive (about 65%) on never having to worry about contracting it again, or you can engineer a way to expose your immune system to the virus the first time so it can build that antibody army and be ready for the smallpox particles waiting to attack – and no one dies (well, at least not anywhere near as many). So vaccination serves as the first exposure to these antigens. Kill the polio virus so it can’t replicate in your cells and give it to people. Engineer a viral shell that looks just like the shell of the human papillomavirus but doesn’t have any DNA inside of it, and give that to people so that when the real thing comes around it will be neutralized very quickly. (How quickly? Take allergies, for example. Allergies are an example of an immune reaction gone haywire. Someone who is genetically susceptible to bee stings can be stung once and be fine – probably some breathing difficulties, maybe a little more swelling than a non-allergic person, but nothing too bad. But as soon as they are stung a second time, within minutes, if not seconds, they will break out with hives and wheezing, and are likely to die if they do not receive immediate medical care. Seconds-to-minutes is the small amount of time it takes for your body to recognize the intruder and respond.)

The important ingredient in vaccines is the inactivated form of whatever bacterial or viral infection it prevents. These are either the real agents, just killed/inactivated (literally, it can be killed bacteria), or they are engineered particles that will still trigger the intended immune response. Take the HPV vaccine, for example. Researchers were able to figure out the genetic code for the viral shell and grow shell-only replicas of the virus, without its enclosed DNA that would infect human cells using yeast (the yeast is the factory that provides the machinery for the viral particles to grow). That shell is still a protein, just like the actual viral shell is. There aren’t any manmade chemicals there. We have just figured out how to utilize various systems to grow bits and pieces of naturally occurring substances. Vaccines also contain solutions to make them stable for transfer, storage, and injection. For Gardasil, the HPV vaccine, Merck states on the package insert that “Each 0.5-mL dose of the vaccine contains approximately 225 mcg of aluminum (as amorphous aluminum hydroxyphosphate sulfate adjuvant), 9.56 mg of sodium chloride, 0.78 mg of L-histidine, 50 mcg of polysorbate 80, 35 mcg of sodium borate, and water for injection. The product does not contain a preservative or antibiotics.” Yes, there are some chemicals there: aluminum (which you ingest from other sources naturally anyway), sodium chloride (table salt), L-histidine (a naturally occurring amino acid you get from meat and other protein sources), polysorbate (an oily liquid used as an emulsifier), sodium borate (another salt, containing sodium and boron, probably for a buffer), and water to make the whole thing liquidy. There are no preservatives (so it has a limited shelf life), and no antibiotics (no reason it should, since you don’t use it to fight bacterial infections). Nothing harmful, at least not any more so than the ingredients you can’t pronounce on a bag of potato chips.

I think I’ve now addressed all of PCJ’s concerns; at least, all the ones in that particular comment. Let’s recap: infant immune systems are just as strong as adult ones, and we are exposed to bazillions of antigens every day, so purposefully exposing a baby to eight more doesn’t do any harm. There are very few chemicals in vaccines, especially these days. There is no harm in vaccinating children, only benefit.

Now let’s ask, “why do we time our vaccines the way we do?” Great question. Take a look at the two-month-old vaccine schedule. Hepatitis B, rotavirus, DTaP, Hib, PCV, IPV. Oh wait, I have to tell you something else first. During development in the uterus, a fetus receives antibodies from its mother. These antibodies will provide extra protection to the infant until it is about 6 months old, at which point they wane.

-Let’s start with Hib. Fifteen years ago, Hib was the #1 cause of meningitis in infants, and everyone who got it did so around 6 months of age. Why? Mom’s antibodies protected them before then, but as soon as they disappeared, Hib was waiting. Hib killed babies; that is a fact. So a baby gets its first dose of Hib at 2 months of age, and it’s a special formulation of the Hib bacterium that evades Mom’s antibodies while stimulating Baby’s. That way, when Mom’s antibodies disappear around 6 months, Baby’s antibodies are ready to go. If unvaccinated older children and adults get Hib, they don’t suffer from as much morbidity (read: don’t get as sick) as infants do, so if you were born prior to the Hib vaccine era, no one’s going to do a catchup immunization on you.

-Rotavirus is also started early, because the only people who die of rotavirus infection are infants, whose bodies can’t handle the intense electrolyte imbalance caused by massive diarrhea as well as adults can. Adults get rotavirus (a guy in my class caught it working at the kids’ hospital this summer and was sick as a dog), but they don’t die from it, so again, we don’t immunize them.

-PCV has the same sort of logic as Hib, but it causes pneumonia. This one also protects against adult disease, because pneumococcus is the #1 cause of pneumonia in adults.

-I can’t give you a good rationale for IPV right now, but the bottom line is that kids get polio, and no one wants polio. Just ask that woman who just turned 60 who’s been living in an iron lung her whole life. Same with diphtheria, tetanus, and pertussis. If you want to know what you’re protecting your child from with the pertussis vaccine, just watch these videos. Just watching the videos makes me sick to my stomach. Breathe, children, breathe!

-Now Hep B is an interesting story. The rationale behind giving Hep B immunizations so early is not that infants are likely to be sharing dirty needles to fuel their heroin addictions. It’s because there are a lot of people infected with Hep B who don’t know it, and they may get pregnant. It's cheaper and easier to vaccinate all babies at birth for Hep B than it is to test every mother and then decide whether to vaccinate. So yes, if you are known to be Hep B negative, you can defer the Hep B shot until your kid is older. (The CDC even says so right on the vaccine schedule.) But why do it? Your immune system is no stronger at age 10 than it is at age 1 month. It just isn't. And as for whether someone can avoid exposure to Hep B their whole life, even given that they never engage in risky sex or use dirty needles, well, that's a matter for debate. One bad blood transfusion, one visit to a foreign country (or an underdeveloped part of the U.S.) with unclean sanitation... that's a pretty big risk.

-Most of the other vaccinations you get as a child have a similar rationale. Rubella (the “R” of MMR) is kind of interesting, on the other hand, in that it actually doesn’t cause any sort of big-deal childhood illness. You get a mild rash with a fever and you’re fine (it’s also called German measles). The problem is that if women get rubella for the first time while they’re pregnant, their babies end up blind and deaf with mental retardation. So we vaccinate girls so they’ll never be sick with rubella while they’re pregnant. And in fact, to completely eradicate the disease, we vaccinate boys, too. Damn carriers.

-One of the newer vaccines available is varicella, which causes chicken pox. Now I know that every one of you reading this is going, “Huh? What’s the problem with chicken pox? We all got chicken pox and we’re fine.” Well, the fact is that infants die of chicken pox. Fetal exposure is a really serious deal – it causes massive morbidity, if the fetus survives to birth. Infants who get chicken pox can die, too. And even if you survive, the course of the illness has a huge effect on the indirect costs of healthcare. (Quick financing primer: direct cost of an illness includes the money it takes to go to the doctor and buy the medicines. The indirect cost includes money lost from parents staying home from work.) When your kid gets sick for two weeks with chicken pox and you need to use up all your vacation days or hire a babysitter (and what babysitter in their right mind wants to care for a sick kid?), you’ll wish your kid didn’t have chicken pox.

So that’s that, people. Vaccinate your children. To me it IS a no-brainer. Still want more information? Here are some reliable sources available to everyone: Wikipedia (medical people use it all the time, and you can usually double-check anything strange you find here from other places on the Internet); MedlinePlus from the National Institutes of Health; the Centers for Disease Control and Prevention; and any of the medical specialty academies (like the American Academy of Pediatrics). Want to find the package insert for a vaccine or drug? Google the name of the product and “package insert” and you should be able to find a pdf of the file. Any more questions? Please, ask!