100

Biology is rarely black or white, all or nothing. Protective immunity is generally not an on/off switch, where from the moment you're vaccinated you're infinitely resistant for the rest of your life. You shouldn't expect that, having received a smallpox vaccine, you could have billions of smallpox viruses squirted directly into your lungs and shrug it off ...


76

Since 2000, in the United States alone, there were 16 reports of outbreaks or groups of outbreaks where the outbreak started with an initial case in an unvaccinated individual and resulted in disease in previously vaccinated individuals. The epidemiology of pertussis is a little different, and transmission happens in many cases apart from a clear outbreak, ...


34

There are different polio vaccines - one live (attenuated) vaccine which is given orally and one inactivated, which is injected. The main reason for using the live orally vaccine is that it provides excellent immunity (better than the inactivated) since it uses the natural infection route (oral-faecal) in the body where it enters through cells in the ...


32

Mainly cost/benefit analysis. Using vaccines has a cost, both in dollars and in risk. That cost may be very low (cheap safe vaccines, like measles vaccine), or may be relatively high (smallpox vaccine is relatively risky, with around a 1 in 300,000 chance of moderate to severe side effects); but there is always some cost. Vaccines may not have any ...


23

The flu virus changes rapidly so that the current vaccine doesn't work against the new strains. The way vaccines work is that they teach our immune system what to look out for. The vaccine contains bits of the virus but in a form that can't cause a proper infection, the body learns what to look for and next time before the virus can really get going the ...


18

Vaccines work by introducing an attenuated strain of the pathogen (or alternatively the antigens that are normally present on the pathogens surface) into the body, whereupon the body mounts an immune response. As this will (hopefully) be the first time that the body has encountered the antigens on the pseudo-pathogen's surface, the response is called the ...


18

Most information here can be found broadly in Cellular and Molecular Immunology, 8th Ed. Here's how the flu vaccine works: Scientists forecast months in advance which strains they think stand to cause the most problems. The vaccine is often trivalent, protecting against three different strains on flu: Two influenza A and one influenza B. You can read about ...


16

The goal of the vaccine is to provoke an immune response, therefore some degree of inflammation is expected in order for the vaccine to work. As swbarnes2 says, vaccines contain adjuvants, pro-inflammatory molecules that produces local inflammation and recruits immune cells to the site of the inoculation. Since you get the shot intramuscularily, ...


15

Duration of efficacy is typically determined by tracking the antibody titers of a cohort of subjects who have gotten the vaccine, and estimating based on the trajectory of those titers where they will eventually cross the threshold to the point where the vaccine no longer confers immune resistance. These estimates do get revised and estimated as time goes ...


14

MBQ and Rory M have already given decent answers on the "hows" of how the vaccine memory is formed. Now, for some twists: There are three (general) types of vaccine, all of which are meant to make your body "think" its being infected and provoke an immune response, while at the same time not causing active infection. They are: Live attenuated. These ...


13

Unfortunately, we do see examples of bacteria and viruses evolving vaccine resistance. For instance, vaccine resistant strains of polio and pertussis have recently been identified. Yet these seem like the exception rather than the rule. One thing that makes it harder for pathogens to evolve resistance is that vaccines usually generate antibodies to ...


13

Eliminating a virus from the world is an immensely costly undertaking. As with most things in real life, cost vs. benefit (and feasibility) need to be taken into account. Unfortunately, there is a limited amount of money available to fight disease. The overall mortality rate of smallpox is about 30%. That's a very high mortality rate, one that shaped ...


11

There is a Wikipedia page on the topic of attenuated vaccines. Basically the idea is that the virus is grown on some sort of foreign host such as cells in culture, eggs or an animal. This selects for mutant viruses, present in the original population, which are pre-adapted to the new host (so that they grow better). By repeating this process several times ...


10

I wish you good luck, as 99.99% of the anecdotal claims out there that conclude vaccination is bad are based on unfounded rumors. Note that much of the negative public opinion is based on a fraudulent (and retracted) paper by Wakefield in The Lancet (1998). Unfortunately for you, however, it is in English. My French is a bit rusty, but if you go to ...


10

I would suspect that it's because not every disease caused by microbes can be treated by vaccines. For example vaccines are not as effective on microbes that cause skin infections because the antibodies generated by being vaccinated travel in the blood and some microbes damage the skin and nearby tissues without going into the circulatory system to be ...


9

Both are forms of immunisation. Inoculation is exactly that. A live organism is introduced in a controlled way, so as to minimise the risk of infection, and is essentially the same process followed by many people in history. It is inherently risky. Vaccination is introducing a weakened version of the pathogen, so that the immune response is triggered and ...


9

Here is a link to the Public Health Statement for Aluminum produced by the Centers for Disease Control and Prevention (CDC) in the United States. There is much more information on the web page but the following are some of the more pertinent points to your question. Potential Health Effects Workers Workers who breathe large amounts of aluminum dusts ...


9

There are a wide variety of different kinds of vaccines. The basic principle is that the human (and more generally, jawed vertebrate) immune system can identify invaders by recognizing and responding to portions of macromolecules on those invaders called antigens. Vaccines use this principle by exposing the immune system to specific antigens ahead of time, ...


8

First let me point out that for the US, I'm not knowledgeable enough to speak for the rest of the world, you are correct. There are no approved live attenuated vaccines mixed with componet/subunit/inactivated vaccines. Background: Before we go into why that's true, let's work a little to show that's true. The FDA publishes a wonderful list of every ...


8

I commented on this question, but the OP's response prompted me to think again. Here is the graph from the document that the OP linked to: Clearly what is confusing is that the parameter referred to as 'antibody level' rises quickly, but not as a step. In terms of the x-axis, vaguely labelled as weeks, it looks as if the level of antibody continues to rise ...


8

In the US, infants are vaccinated against Hep B at birth and again a month or two later as well, because of the risk of maternal transmission. If the mother is known to be HepB positive, HBIG will also be administered. Perinatal HBV transmission can be prevented by identifying HBV-infected (i.e., hepatitis B surface antigen [HBsAg]-positive) pregnant ...


8

Can people with AIDS/HIV be vaccinated? Yes. Immunization is an important part of the overall treatment strategy for HIV positive individuals. HIV infection is a risk factor for a number of vaccine preventable infectious diseases. Immunization in these patients is particularly important because of their increased risk of developing disease. (See Cecil ...


8

(World Health Organisation, 2014. p. 2) shows the adverse effect (side-effect) rates for the MMR vaccine. For instance, fever between the 7th to 12th day after vaccination occurs in 5 to 15% of vaccine recipients and rashes occur in 2-5% of vaccines, etc. Page 6 summarises the results in a table. As you point out, the adverse effects are variable in ...


7

The major reason for this are differences in the preparation methods. Live (attenuated) vaccines need permanent cooling, which makes their use in third world countries difficult. Inactivated vaccines are inactivated either by heat, radiation of chemicals and are often freeze-dried after purification (removal of chemicals used for killing). In this ...


7

As Alan Boyd says, the relatively slow rise is due to gradual uptake of the injected antibody. If you deliver the antibodies by intravenous injection or another mode that allows rapid uptake (I use intraperitoneal injection in mice) then the antibody levels peak rapidly, less than a day and probably a couple hours, and then drop off; there is no continued ...


7

Since another posted answer addresses HepB vaccination at least as effectively as I would have, I'll say something about first-day scheduling for BCG, which is consistent with WHO guidelines (emphasis added): In countries with a high burden of TB, a single dose of BCG vaccine should be given to all infants as soon as possible after birth. Since ...


7

Something which may help is a model. There is a standard model based on a key number called R₀, the basic reproductive number. This is a highly boiled up number which indicates how many uninfected people will be infected by a single infected individual. Trivially, if R₀>1, the disease will spread through society, and if R₀<1, it will vanish because ...


7

A lot of sexually active adults carry one or another strain of HPV but most do not develop cancer. You can carry HPV — and spread it to others — without showing any symptoms yourself: HPV infections are so common that nearly all men and women will get at least one type of HPV at some point in their lives. Most people never know that they have been ...


6

No, it is not true, see references 1 and 2 for this purpose. From these articles which followed up booster vaccinations for pertussis it seems that there is at least some protection 5 and 8 years after the boost. There is another study, which says that 10 years are relatively safe to assume, as the reduction in antibody levels over time estimated from the ...


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