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Immunizations

You can see the diseases, vaccine-preventable diseases in this column and the number of cases reported prior to routine immunization and then the number of cases reported last year in this country. You’ll see a real dramatic decline in these vaccine-preventable diseases. Between 95 and 100% decline and this is due to routine immunization against these diseases. So this is a very dramatic success story, and because of this - this is from the MMWR published by the CDC for seizures.

So the other part of this table is that there are just a few little footnotes and so this does tend to get a little bit complicated and that’s in regards to the individual vaccines. So we are going to talk about those coming up, the individual vaccines. But first I just want to remind you that some kids will come to you and they won’t be up to date on their immunizations. This is a table that’s in the syllabus and shows the catch-up immunization schedule.

In terms of specific vaccines, and we’ll talk about these when indicated, there are hyperimmune globulins with higher titer of antibody. These preparations are for hepatitis B, V-fig, tetanus immune globulin, rabies immune globulin and I hope we’ll have time to talk about RSV immune globulin as well and the specific indications for that. Now we are going to talk about the specific vaccines, and also sometimes we will talk about the specific diseases if they haven’t been covered elsewhere in the course. This is a slide from the CDC showing tonsillar diphtheria and diphtheria is produced, a toxin-mediated disease, by Carinii bacterium diphtheria. This normally causes a respiratory disease. You can get cutaneous diphtheria also, and at other sites. The complication comes from the toxin which is a toxin that may cause myocarditis and other complications. Diphtheria vaccine is a toxoid vaccine, so it is taking the toxin and inactivating it. Therefore vaccination will not prevent colonization but it will prevent disease. There are two vaccine formulations. There is a big D, and you will see that with the DTaP, DTPM and DT vaccines, and then the little d, the TD vaccine and that’s to be used seven years of age.

Next we’ll talk about tetanus. This is a slide also from the CDC which shows a subject with opisthotonos, which is muscle spasm from tetanus. This is a neurotoxin and in pediatrics, one of the main problems with tetanus is neonatal tetanus. And this child has neonatal tetanus. This slide is from the WHO and this shows this child with this sardonic smile of neonatal tetanus.

Finally, you put the D and T together with a pertussis component and you get DTaP vaccine, the acellular pertussis component, and that includes various components of Bordetella pertussis. Including possibly pertussis toxin, filamentous hemagglutinin, pertactin (pertucin?) fimbriae and a variety of combinations of these which we will get to. The main difference with DTaP vaccine and whole cell DTP vaccine is the decreased endotoxin content in the acellular formulation. This is given in a five day series, two for six months, 12-18 months and finally at 4-6 years of age. You do not give pertussis vaccines, at this point, at seven years of age and older. Only less than seven years of age. The efficacy of the DTaP vaccine is similar to DTP vaccine.

The relative contraindications to pertussis vaccine are shown in this slide and this is different from an absolute contraindication. Pertussis, as you know, can be a very severe disease. So depending on a risk of a subject to pertussis and the complications that they could get from the disease, you need to weigh the risks and benefits. But prior vaccine reaction is a relative contraindication. That’s encephalopathy within seven days, a seizure within three days, persistent crying for three or more hours, collapse state or hypotonic hypo-responsive episode, fever greater than or equal to 40.5 C or an anaphylactic reaction. These are relative contraindications to further vaccination with any pertussis component vaccine. Anybody with a known or suspected progressive neurologic disorder or recent seizures. If you give the vaccine it may result in fever. Fever lowers the seizure threshold, this may induce the seizure and it may confuse the clinical picture. So anybody with those conditions or a known or suspected neurologic condition that predisposes to seizures or neurologic deterioration - the common example of that is tuberous sclerosis, where somebody may have tuberous sclerosis and may not show any signs or symptoms but you know that they are at risk for developing them - giving the vaccine may result in lowering the seizure threshold and then you are not sure.

I’m not going to talk much about whole cell DTP vaccine because it’s the old vaccine. Now what’s recommended and is preferred is to use the acellular vaccine because there are less reactions to it. The whole cell vaccine contains endotoxin and does have more reaction. Given in the same series as the acellular vaccine, has the same contraindications and precautions and similar efficacy. But it does have a lot of reactions, as shown in this table. This is a study by Cody and colleagues showing really the high rates of reaction to whole cell DTP vaccine; up to 50% local reactions, half the patients with fever and then systemic reactions, such as drowsiness, irritability, persistent crying. Again, a lot of these reactions due to endotoxin. Give the acellular pertussis component vaccine, you get less reaction and that’s why it’s preferred. But because it’s so reactagenic, in the past it’s been blamed for a lot of other things. Just to clear up some misconceptions; pertussis-containing vaccines do not cause sudden infant death syndrome. Pertussis-containing vaccines do not cause brain damage. There is no causal link between any pertussis component vaccine and brain damage. In the past some practitioners have given half doses of DTP vaccine in an attempt to prevent reaction. Half doses have not been well studied. The immunogenicity and efficacy of that is not well known and therefore you should not give half doses of vaccine.

Now polio vaccine; this is also one of these areas that is really in a state of flux, and a good portion of the polio discussion in the syllabus is about OPV, oral polio vaccine, live vaccine. And there are some changes in that regard that are coming up and therefore for Board review purposes, you have to realize it takes a while for these Board tests to catch up with what’s going on. So if you know the latest information, that’s fine. And if you know the old information, that’s fine too. You are not going to be dinked on that if it’s a transitional period and that’s where we are right now, in a transitional period.

We are going to move on to MMR vaccine. The first part of the M is measles vaccine. And measles vaccine is a live virus vaccine and you may get this live, attenuated, weakened form of the measles virus. It may multiply within the host and actually produce an attenuated case of measles, which you can see a week to 12 days after immunization, with a low grade fever and a mild rash. Seroconversion depends upon the age at which MMR vaccine is given.

For measles vaccine, the precautions and contraindications are shown on this slide. Pregnancy; it’s a live vaccine, so theoretical concerns. Gelatin or a mycin allergy, this will be an anaphylactic allergy. That’s in the vaccine. Thrombocytopenia; measles-containing vaccine may cause a lowering of the platelet count, so in a patient with thrombocytopenia you could think about whether it’s worthwhile to vaccinate them against measles or not.

So now we are going to move on from MMR vaccine and move on to H. influenzae type B vaccine. I haven’t talked much about the science behind a lot of these vaccines and that’s because that’s not important for test-taking purposes. However, with H. flu type B vaccine, that’s different. So I am going to spend a little bit talking about the science behind it. The important thing with H. flu type B in terms of immunity is immunity to the polysaccharides. However if you take the plain polysaccharide and you use that as a vaccine, it’s very weak. You get a very weak antibody response in infants and really don’t get a very good antibody response until 18-24 months of age. If you take this polysaccharide and you bind it to a protein.

So there are several different vaccines in general. It’s not important to know the main differences between them, but there are different manufacturers of the vaccine. The polysaccharide is linked to different protein carriers. Most of these have been used before so there is a lot of clinical experience with them, and that’s why they have been chosen.