FDA suggests revamping COVID vaccinations to once-a-year shot similar to flu cleveland.com
Decreasing rates of childhood immunization are a major concern. Our medical analyst explains why CNN
Top Questions
What is a vaccine?
A vaccine is a suspension of weakened, killed, or fragmented microorganisms ortoxinsor other biological preparation, such as those consisting ofantibodies,lymphocytes, or mRNA,that is administered primarily to preventdisease.
How are vaccines made?
A vaccine is made by first generating the antigen that will induce a desired immune response. The antigen can take various forms, such as an inactivated virus or bacterium, an isolated subunit of the infectious agent, or a recombinant protein made from the agent. The antigen is then isolated and purified, and substances are added to it to enhance activity and ensure stable shelf life. The final vaccine is manufactured in large quantities and packaged for widespread distribution. Learn more about mRNA vaccine creation.
What is a vaccine delivery system?
A vaccine delivery system is the means by which the immune-stimulating agent constituting the vaccine is packaged and administered into the human body to ensure that the vaccine reaches the desired tissue. Examples of vaccine delivery systems include liposomes, emulsions, and microparticles.
How do vaccines work?
A vaccine imitates infection so as to encourage the body to produce antibodies against infectious agents. When a vaccinated person later encounters the same infectious agent, their immune system recognizes it and can fight it off. Learn more.
Summary
vaccine, suspension of weakened, killed, or fragmented microorganisms or toxins or other biological preparation, such as those consisting of antibodies, lymphocytes, or messenger RNA (mRNA), that is administered primarily to prevent disease.
A vaccine can confer active immunity against a specific harmful agent by stimulating the immune system to attack the agent. Once stimulated by a vaccine, the antibody-producing cells, called B cells (or B lymphocytes), remain sensitized and ready to respond to the agent should it ever gain entry to the body. A vaccine may also confer passive immunity by providing antibodies or lymphocytes already made by an animal or human donor. Vaccines are usually administered by injection (parenteral administration), but some are given orally or even nasally (in the case of flu vaccine). Vaccines applied to mucosal surfaces, such as those lining the gut or nasal passages, seem to stimulate a greater antibody response and may be the most effective route of administration. (For further information, see immunization.)
The first vaccine was introduced by British physician Edward Jenner, who in 1796 used the cowpox virus (vaccinia) to confer protection against smallpox, a related virus, in humans. Prior to that use, however, the principle of vaccination was applied by Asian physicians who gave children dried crusts from the lesions of people suffering from smallpox to protect against the disease. While some developed immunity, others developed the disease. Jenners contribution was to use a substance similar to, but safer than, smallpox to confer immunity. He thus exploited the relatively rare situation in which immunity to one virus confers protection against another viral disease. In 1881 French microbiologist Louis Pasteur demonstrated immunization against anthrax by injecting sheep with a preparation containing attenuated forms of the bacillus that causes the disease. Four years later he developed a protective suspension against rabies.
After Pasteurs time, a widespread and intensive search for new vaccines was conducted, and vaccines against both bacteria and viruses were produced, as well as vaccines against venoms and other toxins. Through vaccination, smallpox was eradicated worldwide by 1980, and polio cases declined by 99 percent. Other examples of diseases for which vaccines have been developed include mumps, measles, typhoid fever, cholera, plague, tuberculosis, tularemia, pneumococcal infection, tetanus, influenza, yellow fever, hepatitis A, hepatitis B, some types of encephalitis, and typhusalthough some of those vaccines are less than 100 percent effective or are used only in populations at high risk. Vaccines against viruses provide especially important immune protection, since, unlike bacterial infections, viral infections do not respond to antibiotics.
The challenge in vaccine development consists in devising a vaccine strong enough to ward off infection without making the individual seriously ill. To that end, researchers have devised different types of vaccines. Weakened, or attenuated, vaccines consist of microorganisms that have lost the ability to cause serious illness but retain the ability to stimulate immunity. They may produce a mild or subclinical form of the disease. Attenuated vaccines include those for measles, mumps, polio (the Sabin vaccine), rubella, and tuberculosis. Inactivated vaccines are those that contain organisms that have been killed or inactivated with heat or chemicals. Inactivated vaccines elicit an immune response, but the response often is less complete than with attenuated vaccines. Because inactivated vaccines are not as effective at fighting infection as those made from attenuated microorganisms, greater quantities of inactivated vaccines are administered. Vaccines against rabies, polio (the Salk vaccine), some forms of influenza, and cholera are made from inactivated microorganisms. Another type of vaccine is a subunit vaccine, which is made from proteins found on the surface of infectious agents. Vaccines for influenza and hepatitis B are of that type. When toxins, the metabolic by-products of infectious organisms, are inactivated to form toxoids, they can be used to stimulate immunity against tetanus, diphtheria, and whooping cough (pertussis).
In the late 20th century, advances in laboratory techniques allowed approaches to vaccine development to be refined. Medical researchers could identify the genes of a pathogen (disease-causing microorganism) that encode the protein or proteins that stimulate the immune response to that organism. That allowed the immunity-stimulating proteins (called antigens) to be mass-produced and used in vaccines. It also made it possible to alter pathogens genetically and produce weakened strains of viruses. In that way, harmful proteins from pathogens can be deleted or modified, thus providing a safer and more-effective method by which to manufacture attenuated vaccines.
Recombinant DNA technology has also proven useful in developing vaccines to viruses that cannot be grown successfully or that are inherently dangerous. Genetic material that codes for a desired antigen is inserted into the attenuated form of a large virus, such as the vaccinia virus, which carries the foreign genes piggyback. The altered virus is injected into an individual to stimulate antibody production to the foreign proteins and thus confer immunity. The approach potentially enables the vaccinia virus to function as a live vaccine against several diseases, once it has received genes derived from the relevant disease-causing microorganisms. A similar procedure can be followed using a modified bacterium, such as Salmonella typhimurium, as the carrier of a foreign gene.
Vaccines against human papillomavirus (HPV) are made from viruslike particles (VLPs), which are prepared via recombinant technology. The vaccines do not contain live HPV biological or genetic material and therefore are incapable of causing infection. Two types of HPV vaccines have been developed, including a bivalent HPV vaccine, made using VLPs of HPV types 16 and 18, and a tetravalent vaccine, made with VLPs of HPV types 6, 11, 16, and 18.
Another approach, called naked DNA therapy, involves injecting DNA that encodes a foreign protein into muscle cells. The cells produce the foreign antigen, which stimulates an immune response.
Vaccines based on RNA have been of particular interest as a means of preventing diseases such as influenza, cytomegalovirus infection, and rabies. Messenger RNA (mRNA) vaccines are advantageous because the way in which they are made allows them to be developed more quickly than vaccines made via other methods. In addition, their production can be standardized, enabling rapid scale-up for the manufacture of large quantities of vaccine. Novel mRNA vaccines are safe and effective; they do not contain live virus, nor does the RNA interact with human DNA.
Vaccine-preventable diseases in the United States, presented by year of vaccine development or licensure.
The immune system is the bodys natural defense mechanism. Most of the time, it works efficiently to combat invading pathogens. However, certain pathogens can overwhelm the immune system, causing serious infection and illness.
Vaccines are products that help the immune system combat invading disease-causing pathogens. They are a safe and effective method for preventing certain diseases.
This article outlines what vaccines are and how they work. It will also discuss the various stages that vaccines must go through to receive medical approval.
Vaccines are products that help prevent disease. They do this by preparing the body for exposure to disease-causing pathogens.
Today, vaccines help control and prevent a range of serious diseases. These include but are not limited to:
Vaccines train the immune system to detect and combat disease-causing pathogens. To understand how vaccines work, people will need to know how the immune system works.
Pathogenic viruses and bacteria have molecules on their surface called antigens. These antigens stimulate the immune system to produce proteins called antibodies. The antibodies bind to the antigens, thereby killing or disabling the pathogen.
Different pathogens have different antigens on their surface. A pathogen can only be killed or disabled by an antibody that is capable of binding to its antigens. These antibodies will only exist if the immune system has encountered the antigen in the past.
Vaccines safely expose the body to pathogens so that the immune system can make antibodies capable of binding to their antigens. This allows the immune system to fight off a specific disease-causing pathogen should it encounter that pathogen in the future.
Vaccines expose the body to pathogenic antigens. To do this, they contain one or more of the following:
Vaccine injections contain several other components, including:
It is worth noting that in most cases, the manufacturer will remove the formaldehyde before packaging.
There are four main types of vaccine. These are:
DNA and recombinant vector vaccines are two additional types of vaccine that are still in the experimental stages of development.
Below is a list of current Food and Drug Administration (FDA)-approved vaccines:
It takes about 1015 years to develop a vaccine for a specific disease.
Vaccine development and testing stages vary from country to country. Below is the process for vaccine approval in the United States.
The developmental stage consists of the following three substages:
Approved applications go on to the following three phases of testing:
If the phase III trial is successful, developers will send a Biologics License Application to the FDA. The FDA will then inspect the manufacturing location and either approve or reject the vaccine for labeling.
Once the FDA license a vaccine, inspections and monitoring will continue. Monitoring activities include phase IV trials (such as optional studies for testing safety and effectiveness) and the use of a Vaccine Adverse Event Reporting System (which allows people to report adverse reactions that may be associated with the vaccine).
Vaccines are products that prepare the immune system to detect and eradicate certain disease-causing pathogens. Ultimately, vaccines help reduce the devastating impact of preventable diseases.
Each vaccine must go through a process of development, testing, and monitoring to ensure that it is safe and effective. The FDA will only approve a particular vaccine once it has passed this rigorous process.
