Chapter Excerpt

1

Haemophilus Influenzae Type B
and the HIB Vaccine

WHAT IS HIB?

HIB is a bacterium (singular for bacteria) that can cause serious illnesses such as meningitis (infection of the lining of the brain), blood infections, bone infections, and pneumonia. It is transmitted like the common cold (through contact with an infected person's cough, mucus, or saliva). Fortunately, when a person is exposed to HIB, the bacteria usually remain in the nose, ears, or throat and simply cause minor cold symptoms. Only rarely do they invade farther into the body and cause one of the severe infections mentioned above. Symptoms of these serious infections vary according to the body part that is affected but generally include fever, lethargy, vomiting, and a poor appetite. HIB is diagnosed through a blood test or spinal tap, tests that aren't done until a person is sick enough to go to the doctor. Because most cases of HIB go undiagnosed, no one knows exactly what percentage of minor HIB cases turn serious. This infection does not give a person lifelong immunity. It can be caught more than once.

The HIB Vaccine
American Academy of Pediatrics
2007 Recommended Vaccine Schedule

Birth--Hep B
1--month Hep B
2--months HIB, Pc, DTaP, Rotavirus, Polio
4--months HIB, Pc, DTaP, Rotavirus, Polio
6--months HIB, Pc, DTaP, Rotavirus, Hep B, Flu
1--year MMR, Chickenpox, Hep A
15--months HIB, Pc
18--months DTaP, Polio, Hep A, Flu
2--years Flu
3--years Flu
4--years Flu
5--years DTaP, Polio, MMR, Flu, Chickenpox
12--years Tdap, Meningococcal, HPV (3 doses,
girls only)

IS HIB COMMON?

No, but it used to be. Before the vaccine came into use in the mid- 1980s, there were about 20,000 cases of serious HIB infections each year in the United States. Now we have only about 25 cases each year, almost all occurring in children under age five and most in the first two years. It is very rare beyond age three. HIB can also occur in the elderly. Minor HIB infections (like simple runny noses or coughs) may be more common than this, but they are not tested for or diagnosed because they don't require medical attention.

IS HIB SERIOUS?

Yes. HIB meningitis has about a 5 percent fatality rate, and in about 25 percent of cases, there is some residual brain damage (such as hearing loss, learning problems, or nerve injury). Blood, bone, and lung infections, though less serious, are still potentially fatal. What makes HIB particularly dangerous is that it is difficult to recognize in its early stages. Often a parent can't tell her child has it until he is sick enough to see a doctor. If the child looks seriously ill, the doctor will order invasive testing. After that, it takes one or two days for a lab even to identify HIB in a blood sample.

IS HIB TREATABLE?

Yes. Intravenous antibiotics are given for several days in the hospital. This usually prevents fatalities, but, as in the case of meningitis, some permanent damage can result, especially if the diagnosis and treatment are delayed. In general, when a child is severely ill with a fever in the hospital, IV antibiotics are started right away while the lab tries to identify the infection from blood samples, so treatment for severe HIB disease is usually started before the germ is even identified.

In case you are wondering what the difference is between HIB meningitis and other types of meningitis, I will now tell you. There are dozens of different bacteria, viruses, and fungi that can infect humans and cause meningitis. HIB is just one of these causes, and it almost exclusively affects infants and the elderly. Pc is very similar to HIB.

Meningococcus is a bacterium that can also cause meningitis, and at any age. And there are many other germs that cause meningitis that we don't have vaccines for yet. So, a person can catch any of these other types of meningitis even when fully vaccinated. Viral meningitis happens to be the most common type, and no vaccine yet exists for that.

WHEN IS THE HIB VACCINE GIVEN?

The HIB vaccine is given at two months, four months, six months, and fifteen months. (These intervals may vary slightly.) The last dose can be given anytime between twelve and fifteen months. The PedVaxHIB brand doesn't need to be given at six months because it works a little faster than the other brands. No booster dose is given later in childhood because the disease is almost unheard of beyond age three. This vaccine has been in use since approximately 1985.

HOW IS THE HIB VACCINE MADE?

All companies that make the HIB vaccine start with the same process: The HIB bacteria (presumably originating from an infected person decades ago) are nurtured in a culture medium, also called a petri dish. Batches of bacteria are removed from the petri dish and broken up, and the sugars that form the outer coating of the bacteria are filtered out, collected, and purified. The remaining portions of the bacteria are discarded. The sugars are then put into the vaccine solution.

Here is where the process varies by manufacturer:

ActHIB (Sanofi Pasteur, formerly Aventis Pasteur). Uses an additional tetanus toxoid (a chemical produced by the tetanus bacterium, not the actual bacterium itself) and attaches this toxoid to the HIB sugars.

PedVaxHIB (Merck). Takes a bacterium called Neisseria, breaks it up, and collects some proteins from the outer covering of the bacteria. These proteins are then bonded to the HIB sugars.

WHY SO MANY DOSES?

Why do we give so many doses of a vaccine? In most cases, each shot creates only partial immunity to the disease, and subsequent shots build on that immunity. Some shots, like those for measles, mumps, and rubella and chickenpox, don't require a whole series to create immunity. This is because they are live-virus vaccines, which work well with one initial dose and sometimes a booster years later. As a general rule for shots that come in a series, the first dose provides approximately 50 percent immunity, the second dose bumps it up to about 75 percent, and the third dose gives around 90 percent immunity. A few diseases require a fourth dose about a year after the third, and then another booster dose about four years later. These are necessary to keep immunity levels high enough to be effective.

HibTITER (Wyeth). Uses a toxoid from the diphtheria bacterium (just like the ActHIB product uses a tetanus toxoid) to bind with the HIB sugars. Wyeth stopped making the HibTITER brand last year, and right now it has no plans to resume production. I don't know the reasons for this, but I have included the information here in case those of you with older children who may have received this vaccine want to look back at their vaccine record and read the details.

Why is the tetanus, Neisseria, or diphtheria part needed? They help the body's immune system recognize the HIB sugars and create a better response to the vaccine. The extra germ parts do not create any significant immunity themselves.

WHAT INGREDIENTS ARE IN THE FINAL VACCINE SOLUTION? The ActHIB brand contains:

• HIB sugar/tetanus toxoid complex

• Sugar water

• Saline solution (salt water)

The PedVaxHIB brand contains:

• HIB sugar/Neisseria protein complex

• Saline solution

• Aluminum-225 micrograms (This makes the vaccine work a little better.) A microgram is 1/1000 of a milligram. (You probably can't picture how much that is. Neither can I.)

The HibTITER brand contains:
• HIB sugar/diphtheria toxoid complex

• Saline solution

DIFFERENT TYPES OF VACCINES

There are four main types of vaccines. The first is called a "polysaccharide conjugate vaccine." This type uses only the sugars from the bacteria and bonds (conjugates) them to portions of another germ. It does not contain the entire germ, so there is no way to become infected with the disease from this vaccine. A second type of vaccine is a "live-virus vaccine." This vaccine contains the whole, living virus. It can actually give a person the infection, although fortunately that rarely happens. A third vaccine type contains the whole germ, but it has been killed, so it can't infect you. The fourth type of vaccine is called a "recombinant vaccine." It is genetically engineered and doesn't contain any portion of the original germ, though it does have some manufactured proteins that match the germ's proteins. As we go through the book, I will tell you which type of vaccine each one is. HIB is a polysaccharide conjugate vaccine.

Are any of these ingredients controversial?

The only item that is a potential problem is the aluminum in the PedVaxHIB brand. Although research has not proven that the aluminum in vaccines is harmful, some studies indicate that when too many aluminum-containing vaccines are given at once, toxic effects can occur.

WHAT ARE THE SIDE EFFECTS OF THE HIB VACCINE?

This vaccine has one of the safest side effect profiles. The standard reactions, which occur in about 5 percent of babies, include fever, fussiness, redness and swelling, etc. ("Et cetera? What do you mean, 'et cetera'?" you may be asking right now. You don't want to just hear "et cetera" when it comes to possible side effects your child may experience. That's like a doctor telling you, "Your medicine may cause some side effects, but don't worry about it." On page 180 I go into more detail about the standard side effects that apply to all vaccines.)

Fortunately the HIB vaccine causes few serious reactions. The only serious side effects that have been reported are:

• Guillain-Barré syndrome. This disorder causes severe muscle weakness and paralysis.

• Serious HIB infection. In the vaccine trials, more babies who received the vaccine caught a serious HIB infection than those who didn't get the vaccine. However, these infants didn't get infected by the vaccine itself. Research shows that while the vaccine is beginning to work on the immune system, the immune system can't react to a natural HIB infection for a period of five days. An immunized infant is therefore susceptible to catching natural HIB for a few days while her immune system is "distracted" by the vaccine. This may have been a problem back when HIB disease was common, but now that HIB is rare, the chance that a baby would be exposed to HIB during the few susceptible days after vaccination is minuscule. See "Resources," page 263, for the details on three studies in The Journal of Pediatrics and The New England Journal of Medicine about this side effect.

SHOULD YOU GIVE YOUR BABY THE HIB VACCINE?

Even though I pose this question in each chapter, I'm not going to answer it for you. Instead, I am going to present the logical points from both sides so you can make an informed choice.

Now, in case you are wondering exactly how I would know the reasons some people choose not to get a vaccine, I'll tell you. Whenever I meet a parent who doesn't vaccinate (or only partially vaccinates) her child, I like to pick her brain a little to see how she thinks. I've written down many responses over the years, and I've recorded the thoughtful and logical ones in this section of each chapter. (I've purposely left out any of the really, shall we say, "interesting" ideas. Although the inclusion of such interesting comments would be sure to entertain and amuse you-like the one about germs not really causing infections; they're just a normal and harmless part of our everyday existence, so the shots aren't needed to prevent them-some of them might just confuse the heck out of you, and this book is all about unconfusion.)

Reasons to get this vaccine

Obviously meningitis and blood infections are very serious. There are many germs out there that cause these conditions, and HIB used to be the most common one. Although HIB is now extremely rare, continued vaccination keeps the disease out of our population and will help protect your baby from the rare chance he may catch this germ. This shot also has the safest side effect profile of all the vaccines, and the ingredients are very pure compared with those found in most other vaccines.

Reasons some people choose not to get this vaccine

Probably the main reason some parents choose to skip this vaccine is that severe cases of this disease are now extremely rare (about 25 cases per year in the United States in kids under five years of age). A breastfed baby who does not attend day care is at a particularly low risk of catching this illness.

TRAVEL

Most of the information I provide regarding each disease pertains to people living in the United States. So, if I tell you a certain disease is rare and your child is at low risk of catching that disease, I am assuming that you are not planning to go be a missionary in Africa. In the case of each disease and vaccine, I briefly discuss whether you should be worried about that disease if you travel.

When I say "travel," I don't mean vacation travel. Staying in hotels or on cruise ships and doing the normal tourist sightseeing doesn't typically put you in contact with the local diseases. But if you are planning to visit or live with relatives around the world for an extended period, or if you plan to live with the locals in the jungle for several weeks at a time, then you should carefully investigate the incidence of diseases there and consider vaccination for your child if she isn't fully vaccinated. In general, you need to begin vaccinating about three months before you travel in order to get adequate protection from a vaccine series. You can obtain more information about specific diseases in other countries at www.cdc.gov/travel/diseases.htm.

What about airplane travel itself? Flying for several hours and breathing the recirculated air theoretically could be risky for an unvaccinated baby. But this risk is probably very small. I'm not sure anyone has specifically researched this, however. If you have decided not to vaccinate your baby, I wouldn't say flying is risky enough for you to change your mind. In fact, flying is generally considered okay for a newborn baby, who is too young to have had any shots yet.

Travel considerations

While this disease is rare in the United States, it is still common in most other countries, since very few countries use the HIB vaccine. In my opinion, vacation travel doesn't pose much risk, but if you are planning to live with the locals for a while anywhere else in the world, you should consider the HIB vaccine for your infant if not yet vaccinated.

Options to consider when getting this vaccine If you wish to be very cautious, you might want your baby to get only one or two aluminum-containing vaccines at a time. (See chapter 19 for how to make sure you get only one at a time.) Also, you can try to use an aluminum-free brand whenever possible.

You have the option of getting the HIB vaccine in combination with the DTaP and polio vaccines in one injection instead of as three separate shots. This mix is called Pentacel (made by Sanofi Pasteur). Pentacel has been used in Canada for many years and has recently been approved for use in the United States. The only drawback to this particular mix is that it contains 1500 micrograms of aluminum. See page 40 for more details on this vaccine.

You also have the option to get Comvax (Merck). It is a combination of the HIB (PedVaxHIB brand; see page 5) and hep B (Recombivax brand; see page 54) vaccines in one shot. The manufacturing, ingredients, and side effects are the same as for the individual shots. This combination shot decreases the overall exposure to aluminum to 225 micrograms. Administered separately, the same Merck brands of HIB and hep B contain 475 micrograms of aluminum.

Another option to decrease the number of injections is the Tri- HIBit vaccine (Sanofi Pasteur). If your doctor uses the Tripedia brand of the DTaP vaccine (see page 33) and the ActHIB brand of the HIB vaccine (see page 5), these two can be mixed into one syringe for the eighteen-month dose (the fourth dose in the series). They can't be combined for the first 3 doses. The overall ingredients are the same as in the separate injections, but the number of injections is decreased by one. Any baby will appreciate that.

THE WAY I SEE IT

HIB is a bad bug. Fortunately, it's also a rare bug, so rare that I haven't seen a single case in ten years. Ongoing use of this vaccine in our country helps keep it that way. The HIB vaccine is one of the very safest we have. The ingredients aren't too strange, and the known side effects are minimal. Since the disease is so rare, HIB isn't the most critical vaccine. But it's definitely high on the Top Ten list.

Copyright © 2007 By Robert Sears, M.D.