Table of contentsLive attenuated vaccinesDamaged or inactivated vaccinesSubunit and conjugate vaccinesLive attenuated vaccinesAttenuated vaccines can be made in a variety of ways. Some of the most common methods include passing the pathogenic virus through a series of cell cultures or animal embryos (usually chicken embryos). Taking chicken embryos as an example, the virus develops in different embryos in succession. With each passage, the virus gets better at replicating in chicken cells but loses its ability to replicate in human cells. A virus intended for use in a vaccine can be grown by “passaging” through more than 200 different embryos or cell cultures. Ultimately, the attenuated virus will be unable to reproduce properly (or at all) in human cells and may be used in a vaccine. All methods involving passing a virus through a non-human host produce a version of the virus that can still be recognized by the human immune system, but which cannot be properly reproduced in a human host. When the resulting vaccine virus is administered to a human, it will not be able to replicate sufficiently to cause disease, but it will still provoke an immune response capable of protecting it against future contamination. Say no to plagiarism. Get a tailor-made essay on "Why violent video games should not be banned"? Get the original essay One concern to consider is the possibility of the vaccine virus returning in a form capable of causing disease. Mutations that can occur when the vaccine virus replicates in the body can lead to more virulent strains. This is very unlikely, because the reproduction capacity of the vaccine virus is limited. However, it is taken into account when developing an attenuated vaccine. It should be noted that mutations are quite common with oral polio vaccine (OPV), a live vaccine consumed instead of an injection. The vaccine virus can mutate into a virulent form and lead to rare cases of paralytic poliomyelitis. As a result, OPV is no longer used in the United States and has been replaced by inactivated polio vaccine (IPV) in the adult childhood immunization program. Protection from a live attenuated vaccine generally exceeds that provided by a dead or inactivated vaccine. Inactivated vaccinesAn alternative to attenuated vaccines is a dead or inactivated vaccine. Vaccines of this type are generated by inactivating a pathogen, usually using heat or chemicals such as formaldehyde or formalin. This destroys the pathogen's ability to replicate, but keeps it "intact" so that the immune system recognizes it. (In general, “inactivated” rather than “killed” is used to refer to vaccines of this type, because the viruses are generally not considered live). Since lethal or inactivated pathogens cannot be reproduced at all, they cannot revert to a more infectious form capable of causing disease (as discussed above with live attenuated vaccines). However, they tend to offer less protection against live vaccines and are more likely to require stimulants to create long-term immunity. Vaccines vaccinated or inactivated in the U.S. childhood immunization program include inactivated polio vaccine and seasonal influenza vaccine (in injection form). Some bacterial diseases are not directly caused by the bacteria itself, but by a toxin produced by the bacteria. A.