101

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 ...


77

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, ...


52

Roni Saiba's answer does a good job of explaining what goes into current vaccine development and why it takes so much effort, but I want to directly address the question of why we can't just grow some virus, kill it with UV and have a protective vaccine. The answer is that not all immune responses to viral antigens are helpful in fighting infections of that ...


40

While the existing answers are great and cover a lot of the difficulties in vaccine development, I feel that they fail to address (or at least sufficiently emphasize) the fundamental misconception at the core of the question: If that's the case, why does it take so much time and effort to develop a vaccine, for example, against covid-19? The answer to that ...


36

There is little motivation right now for vaccination against plague because: Human infections with plague are fairly rare. A vaccine administered to the general populace would have to be very cheap and extremely safe to make it cost-effective and have a net benefit given the risks of plague are so low, and because Antibiotics are effective against plague - ...


35

Answering my own question after reading the 2018 Nature review article “mRNA vaccines — a new era in vaccinology” The resources and motivation engendered by the COVID-19 pandemic are a major factor in the development of the first mRNA vaccines approved by national governments. However, before the COVID-19 pandemic, there were recent advances in mRNA vaccine ...


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 ...


26

Vaccine efficacy Pfizer's target measures for efficacy (see the study on clinicaltrials.gov) seem to be: Confirmed COVID-19 in Phase 2/3 participants without evidence of infection before vaccination Confirmed COVID-19 in Phase 2/3 participants with and without evidence of infection before vaccination From Pfizer's study plan (VE = vaccine efficacy): VE ...


24

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 ...


19

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 ...


18

Short answer: Chimpanzees are indeed closer, but perhaps...too close. Almost all invasive research on non-human great apes has halted for some time over ethical concerns. Rhesus macaques are the main non-human primate still used in research (some others are also used, like marmosets). "Pretty much the closest" is in reference to which species are available ...


18

While it is true that deactivated (e.g. heat killed viruses) are used in some cases, the Pfizer, Moderna vaccines are in fact mRNA vaccines. The figure below from the Oxford website details the processes involved in vaccine their DNA based vaccine development. This Moderna page has a video detailing their approach as well. Pfizer also has a nice video ...


16

There is already plague vaccine in use, which is only administered to lab workers working on Y. Pestis or people residing in areas affected with plague. (Via: https://www.cdc.gov/mmwr/preview/mmwrhtml/00041848.htm) Plague can also be treated with antibiotics if detected at earlier stage (such as streptomycin, ciprofloxacin, gentamicin or doxycycline). Very ...


14

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 ...


12

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 ...


11

There are multiple challenges presented, and many of those are not limited to coronavirus vaccine. As mentioned above, it just takes time. Before a vaccine can be used in patients, clinical trials must be performed to validate the safety and efficiency of the vaccine candidate. A Clinical trial includes three phases, which again, just takes time. But to ...


11

To enhance stability and translation efficiency according to {1}: The 5′UTR (TEV) [8,21] and 3′ UTR (F-I) of this construct have been shown to enhance stability and translation efficiency, as has the 100-nucleotide poly(A) tail interrupted by a short linker (A30LA70, where L = GCAUAUGACU) [22] References: {1} Stadler, C., Bähr-Mahmud, H., Celik, L. et al. ...


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 ...


10

Vaccine development is not as easy as just inject some inactivated virus as: Vaccine can have side effects such as inflammatory reactions. So for a good vaccine the side effects must be negligible or within a tolerable limit. Vaccine may not induce immune response. It may be ignored by the immune system as just some random debris. So a good vaccine must ...


10

It means protection against the virus brought to you by the vaccination. Around 45.000 people participate in the trial; 50% of these are vaccinated with the trial vaccine and 50% receive a placebo. Additionally, you exclude people from the trial who had had COVID-19 before. Because infecting people with a potentially deadly disease is not possible ethically, ...


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

Contrary to many beliefs our immune system needs no "training". It is permanently active and confronted with dozens to hundreds of antigens in our food, from dust we inhale and so on. This all happens to protect our body from the environment and the immune system is pretty efficient with that and certainly it is not getting lazy. By vaccinating against a ...


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

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 ...


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, ...


9

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 ...


9

Simple answer: This vaccine trial compared their trial vaccine against saline. See the original publication by Biontech and Pfizer in the New England Journal of Medicine linked below. The relevant information can be found in the methods section: TRIAL PROCEDURES With the use of an interactive Web-based system, participants in the trial were randomly ...


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