Hib vaccine

- [Voiceover] The Hib vaccine was developed in 1985 and it's a vaccination for Haemophilus influenzae type b. Now this specific strain of this bacteria, Haemophilus influenzae, was very serious. It could cause severe complications and diseases. For example, this strain could cause severe meningitis, which is swelling of the tissue that surrounds the brain. And it could also cause pneumonia, which is swelling of the lung tissue caused by this bacterial infection. And epiglottitis, which is swelling of the epiglottis, which is that little covering that folds over the airway whenever we swallow so that food doesn't get into our lungs. Before the development of this vaccine, about 40 to 100 of 100,000 people could become infected by this strain of Haemophilus influenzae. Now that may not seem like a lot, but because it causes such severe conditions, and also because it primarily affects newborns and children, this was a very serious public health concern. But after the development of this vaccine, that number was reduced to less than one case per 100,000 people per year. So that's a reduction from about .04% of the population to .0001% of the population, which is a dramatic difference. Now the way this vaccine works is by inducing an immune response to a specific polysaccharide sequence that is found on this specific strain of Haemophilus influenzae. So what all that means is essentially there is a carbohydrate sequence and this is commonly found on the surface of the bacteria. Now since this polysaccharide sequence, this carbohydrate sequence, is found specifically on the type b strain of Haemophilus influenzae, we want to target this sequence. Because if our immune system can recognize this, if the real deal comes along, then it will be able to eliminate this. However, the problem with a polysaccharide sequence is it doesn't produce a large immune response. Our body is better at recognizing foreign proteins rather than carbohydrates. And so what we do to amplify this response is we attach a little protein with a molecular bond to link the two together. This conjugation, this combining of these two, the polysaccharide and the protein is called a conjugate. They're combined together. So this type of vaccine is a conjugated vaccine that creates a larger immune response. And due to this conjugation, the Hib vaccine is more than 95% efficacious. Meaning it's very effective against stopping the bacteria. But keep in mind, this is all for only the type b strain. All the other types of Haemophilus influenzae can still afflict the patient. But it's really the type b strain that's the most severe and so it's good that we were able to develop a vaccine for it. Now like I said, our immune system can recognize foreign proteins much better than it can polysaccharides. So this creates a huge immune response and causes white blood cells, known as macrophages, to recognize this and engulf it. Macrophage means big eaters. So these big eaters eat up this polysaccharide and protein link. And once these guys do that, they'll travel all the way down the bloodstream into lymph nodes. And in those lymph nodes are specialized white blood cells. And these specialized white blood cells are called T-cells. Once macrophages present this material to T-cells, the T-cells become activated. And these activated T-cells will let other cells, known as B-cells, know that there's something going on here. B-cells are famous for creating antibodies. And antibodies are little Y-shaped proteins that recognize specific sequences. And in this case these B-cells, these antibodies that they create, recognize the specific sequence for these proteins and polysaccharides. And so that's how the immune response is generated. And another way to create a greater response is to introduce this protein and polysaccharide mix multiple times. Now before I go into the dosing, let me highlight this again, remember this is the HI, Haemophilus influenzae, strain b polysaccharide. Now to create a really good immune response, these proteins are often from other viruses or products from bacteria. So for example, some bacterias create a toxin, such as diphtheria, pertussis, or tetanus, which is essentially a protein that creates a huge immune response. So there are actually a lot of vaccines out there for Haemophilus influenzae type b and they may be paired with different types of toxins, whether they're tetanus, pertussis, diphtheria, sometimes this protein can be an inactive virus, so hepatitis B, all sorts of different combinations. And it's also very useful to pair these different proteins and polysaccharides, because not only will the patient get immunization from Haemophilus influenzae, but they'll also get immunization from these other bacteria or viruses that are paired with this polysaccharide sequence. Now in order to generate a very strong immune response, and since a polysaccharide sequence generates a very weak response, the Hib vaccine needs to be dosed three times. And then again with an additional booster vaccine. A booster essentially contains the same components, but it reminds the immune system hey, you need to keep creating antibodies. Keep creating these little signal markers to identify this polysaccharide sequence and allow the immune system to destroy it. And since newborns and very young children are at a higher risk for Haemophilus influenzae strain b, the first dose starts at two months of age. After that initial dose, it's recommended that the patient gets another dose four weeks after that initial dose. So four weeks will be about at four months, and then six months. And remember, this is all to create a very strong immune response to make sure that the baby has immunity against this bacteria. After these three doses, the final booster dose is recommended at 15 to 18 months of age. Now what if the patient actually misses one of these doses? What if the child is about four months old? Well that's OK, you can start the dosing at four months and then just have an extra dose four weeks from then. So if the child gets the first dose at 4 months, they should receive the next dose at six months, and then the next dose at eight months. And then follow up with a booster at 15 to 18 months. Now if the child is about seven to 11 months old, then you'll actually skip one of these doses. And again, the reason for that is because these doses are trying to get the baby through the first months of life without being infected by this bacteria. So if they're already seven to 11 months old, we just need to get them through a couple more months before they get their booster shot. So a seven to 11 month old will only need two vaccines plus the booster. And if the child is 12 to 14 months old, then they'll only need one shot plus the booster. And if the child has missed all the opportunities to get these regular shots, so if they're around 15 months to five years old, then all they need is just one shot, which would be the booster shot. And finally, since children normally develop immunity to Haemophilus influenzae type b after five years old, if they're older than five, then they no longer need to get the vaccine unless they're immunocompromised. Then they may actually need to get the vaccine. Now with any vaccine, there can be some adverse effects. But for vaccines such as this, the benefit really does outweigh the risk. Some more common adverse effects include local pain or redness or swelling around the area of injection. And patients may also develop a fever, they may become fussy or very irritable. And these symptoms may actually be common. Up to 25% of patients may actually have some of these symptoms. But thankfully these usually go away between 24 to 48 hours. Still, it's important to report these symptoms to the physician so that they're aware of any adverse effects and can act quickly if symptoms become worse or do not go away. Now more severe symptoms are the neurological symptoms. And these symptoms include extreme lethargy, inconsolable crying, paralysis of the limbs, seizure, convulsions, very severe adverse effects. Or if a patient develops difficulty breathing or a severe rash, or a fever over 105 degrees Fahrenheit, or 40 degrees Celsius is very serious. But thankfully, these symptoms are very rare and don't occur in patients very often. And as I said, the benefit of the vaccine highly outweighs the risk. Otherwise the patient may develop severe illnesses such as meningitis, pneumonia, or epiglottitis, which can be very life-threatening illnesses.