Live attenuated vaccines

Varicella zoster vaccines Live attenuated strain of Herpes virus... 

Measles vaccines Live attenuated strains of measles virus Active immunization against measles... 

Mumps vaccine Live attenuated strain of the mumps virus Paramyxovirus parotitidus) Active immunization against mumps... 

Rotavirus vaccines Live attenuated strains of rotavirus Active immunization against rotavirus (causes severe childhood diarrhoea)... 

The active immunity may be acquired following clinical infection (chicken pox, rubella, measles), following subclinical infection (polio and diphtheria) and following immunization with an antigen which may be killed vaccine, live attenuated vaccine or a toxoid. 

Various oral rotavirus vaccines (live attenuated rotavirus vaccines, including rhesus rotavirus and bovine rotavirus strains serotype 1 bovine-human rotavirus reassortant vaccine and both rhesus rotavirus monovalent and tetravalent reassortant vaccines) have been evaluated in clinical trials (SEDA-21, 292). 

MEASLES VIRUS VACCINE, LIVE, ATTENUATED (Attenuvax)... 

Venezuelan Equine Encephalomyelitis Vaccine, Live, Attenuated. 

Measles, Mumps, Rubella. Live, attenuated vaccines are used for simultaneous or separate immunization against measles, mumps, and mbeUa Hi children from around 15 months of age to puberty. Two doses, one at 12—15 months of age and the second at 4—6 or 11—12 years are recommended Hi the United States. 

Live attenuated vaccines for RSV are also being developed. Most of these vaccine candidates are derived from cold adaptation, by passing the vims at progressingly lower temperatures than human body temperatures. However, other means of mutagenesis have been used to generate vaccine candidates (72). Several clinical trials of these vaccines are also in progress (73,74). 

An example of the use of an attenuated virus is the administration of the measles vaccine to an individual who has not had measles. The m easles (rubeola) vaccine contains the live, attenuated measles virus. The individual receiving the vaccine develops a mild or modified measles infection, which then produces immunity against the rubeola virus. The measles vaccine protects 95% of the recipients for several years or, for some individuals, for life. An example of a killed virus used for immunization is the cholera vaccine. This vaccine protects those who receive the vacdne for about 3 to 6 months. 

The harvest is a very eomplex mixture of bacterial cells, metabolic products and exhausted medium. In the ease of a live attenuated vaccine it is innocuous and all that is necessary is for the baeteria to be separated and resuspended in an appropriate menstmum, possibly for freeze-drying. In a vaccine made Irom a pathogen the harvest may be intensely dangerous and great care is necessary in the following procedures. 

Cell cultures provide infeeted fluids that eontain little debris and can generally be satisfactorily clarified by filtration. Beeause most viral vaccines made fiom cell cultures consist of live attenuated vims, there is no inaetivation stage in their manufacture. There are, however, two important exeeptions inaetivated poliomyelitis vims vaccine is inactivated with dilute formalin or /3-propiolaotone and rabies vaccine is inactivated with /3-propiolactone. The preparation of these inaetivated vaccines also involves a concentration stage, by adsorption and elution of the vims in the case of poliomyelitis vaccine and by ultrafiltration in the case of rabies vaceine. When processing is complete the bulk materials may be stored until needed for blending into final vaccine. Because of the lability of many vimses, however, it is necessary to store most purified materials at temperatures of-70°C. 

With attenuated viral vaccines the potential hazards are those associated with reversion of the virus during production to a degree of virulence capable of causing disease in vaccinees. To a large extent this possibility is controlled by very careful selection of a stable seed but, especially with live attenuated poliomyelitis vaccine, it is usual to compare the neurovirulence of the vaccine with that of a vaccine known to be safe in field use. The technique involves the intraspinal inoculation of monkeys with a reference vaccine and with the test vaccine and a comparison ofthe neurological lesions and symptoms, if any, that are caused. If the vaccine causes abnormalities in excess of those caused by the reference it fails the test. 

Disadvantages associated with the use of live vaccines are also apparent. Live attenuated vaccines, administered through the natural route of infection, will be replicated in the patient and could be transmitted to others, ff attenuation is lost during this replicative process then irrfectiorrs rrtight result (see poliomyelitis, below). A second, major disadvantage of live vaccines is that the course of their action might be affected by the infeetion and immunological status of the patient. 

Polio is the only disease, at present, for which both hve and killed vaccines compete. Since the introduction of the killed vims (Salk) in 1956 and the live attenuated virus (Sabin) in 1962 there has been a remaikable decline in the incidence of poliomyelitis (Fig. 16.1). The inactivated polio vaccine (TPV) contains formalin-killed poliovirus of all three serotypes. On injection, the vaccine stimulates the production of antibodies of the IgM and IgG class which neutrahze the vims in the second stage of infection. A course of three injections at monthly intervals produces long-lasting immunity to all three poliovirus types. 

Three typhoid vaccines are available currently for use in the United States (1) an oral live-attenuated vaccine (Vivotif Berna-TM vaccine, Swiss Serum and Vaccine Institute), (2) a parenteral heat-phenol-inactivated vaccine (Typhoid Vaccine, Wyeth-Ayerst), and (3) a parenteral capsular polysaccharide vaccine (Typhim Vi, Pasteur Merieux). Immunization is recommended only for travelers going to endemic areas such as Latin America, Asia, and Africa household contacts of a chronic carrier and laboratory personnel who frequently work with S. typhi.13... 

Healthy individuals 5 to 49 years of age can receive the live attenuated influenza vaccine instead of the inactivated vaccine. There are limited data on transmission of the vaccine strain following intranasal vaccination however, secondary transmission does not appear to be a concern. 

The varicella vaccine is made up of an attenuated Oka strain of varicella zoster virus. This is a live attenuated vaccine. Attenuation was achieved by performing serial passages through human embryonic lung cells, embryonic guinea pig cells, and human diploid cells. 

Bacille Calmette-Guerin (BCG) A vaccine prepared from a living attenuated strain of tubercle bacilli and used to vaccinate human beings against tuberculosis or treat some types of cancer. 

Vaccination to induce an adaptive immune response is expected for a broad range of infectious diseases and cancers. Traditional vaccines are mainly composed of live attenuated viruses, whole inactivated pathogens, or inactivated bacterial toxins. In general, these approaches have been successful for developing vaccines that can induce an immune response based on antigen-specific antibody and cytotoxic T lymphocyte (CTL) responses, which kill host cells infected with intracellular organisms (Fig. 1) [1,2], One of the most important current issues in vaccinology is the need for new adjuvants (immunostimulants) and delivery systems. Many of the vaccines currently in development are based on purified subunits, recombinant... 

Many of the more prominent vaccine preparations in current medical use consist of attenuated viral particles (Table 13.6). Mumps vaccines consist of live attenuated strains of Paramyxovirus parotitidis. In many world regions, it is used routinely to vaccinate children, often a part of a combined measles, mumps and rubella vaccine. 

The two vaccines currently available for prevention of influenza are the trivalent influenza vaccine (TIV) and the live-attenuated influenza vaccine (LAIV). The specific strains included in the vaccine each year change based on antigenic drift. 

LAIV, live-attenuated influenza vaccine TIV, trivalent influenza vaccine. 

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