different types of vaccines

8/11/2019 Different Types of Vaccines

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Different Types of Vaccines

WHO via Images from the History of Medicine (NLM)Preparation of measles vaccine

The first human vaccines against viruses were based using weaker or attenuated viruses to generateimmunity. The smallpox vaccine used cowpox, a poxvirus that was similar enough to smallpox to protectagainst it but usually didn’t serious illness. Rabies was the first virus attenuated in a lab to create a vaccinefor humans.

Vaccines are made using several different processes. They may contain live viruses that have beenattenuated weakened or altered so as not to cause illness!" inactivated or killed organisms or viruses"inactivated toxins for bacterial diseases where toxins generated by the bacteria, and not the bacteriathemselves, cause illness!" or merely segments of the pathogen this includes both subunit and con#ugatevaccines!.

Vaccine type

Vaccines of this type on U.S. Recommended Childhood (ages 0-6)

Immunization Schedule

i!e" attenuated

Measles, mumps, rubella (MMR combined vaccine)Varicella (chickenpox)

Influenza (nasal spray)

Rotavirus

Inacti!ated#$illed

Polio (IPV)

epatitis !

%o&oid (inacti!ated to&in) "iphtheria, tetanus (part of "#aP combined immunization)

Su'unit#conugate

epatitis $

Influenza (in%ection) Haemophilus influenza type b (ib)

Pertussis (part of "#aP combined immunization)

PneumococcalMenin&ococcal



Vaccine type the* a!aila'le !accines

i!e" attenuated

'oster (shin&les)

ello fever

Inacti!ated#$illed Rabies

Su'unit#conugate uman papillomavirus (PV)$ive, attenuated vaccines currently recommended as part of the %.&. 'hildhood (mmuni)ation &cheduleinclude those against measles, mumps, and rubella via the combined **R vaccine!, varicellachickenpox!, and influen)a in the nasal spray version of the seasonal flu vaccine!. (n addition to live,attenuated vaccines, the immuni)ation schedule includes vaccines of every other ma#or type+see the tableabove for a breakdown of the vaccine types on the recommended childhood schedule.

The different vaccine types each reuire different development techniues. -ach section below addressesone of the vaccine types.

Live, Attenuated Vaccines

ttenuated vaccines can be made in several different ways. &ome of the most common methods involvepassing the disease/causing virus through a series of cell cultures or animal embryos typically chickembryos!. %sing chick embryos as an example, the virus is grown in different embryos in a series. 0ith eachpassage, the virus becomes better at replicating in chick cells, but loses its ability to replicate in human cells.

virus targeted for use in a vaccine may be grown through+1passaged2 through+upwards of 344 differentembryos or cell cultures. -ventually, the attenuated virus will be unable to replicate well or at all! in humancells, and can be used in a vaccine. ll of the methods that involve passing a virus through a non/humanhost produce a version of the virus that can still be recogni)ed by the human immune system, but cannotreplicate well in a human host.

0hen the resulting vaccine virus is given to a human, it will be unable to replicate enough to cause illness,but will still provoke an immune response that can protect against future infection.

5ne concern that must be considered is the potential for the vaccine virus to revert to a form capable ofcausing disease. *utations that can occur when the vaccine virus replicates in the body may result in morea virulent strain. This is very unlikely, as the vaccine virus’s ability to replicate at all is limited" however, it istaken into consideration when developing an attenuated vaccine. (t is worth noting that

mutations are somewhat common with the oral polio vaccine 56V!, a live vaccine that is ingested instead of in#ected. The vaccine virus can mutate into a virulent form and result in rare cases of paralytic polio. 7or thisreason, 56V is no longer used in the %nited &tates, and has been replaced on the Recommended'hildhood (mmuni)ation &chedule by the inactivated polio vaccine (6V!.6rotection from a live, attenuated vaccine typically outlasts that provided by a killed or inactivated vaccine.

Killed or Inactivated Vaccines

5ne alternative to attenuated vaccines is a killed or inactivated vaccine. Vaccines of this type are created byinactivating a pathogen, typically using heat or chemicals such as formaldehyde or formalin. This destroysthe pathogen’s ability to replicate, but keeps it 1intact2 so that the immune system can still recogni)e it.1(nactivated2 is generally used rather than 1killed2 to refer to viral vaccines of this type, as viruses aregenerally not considered to be alive.!

8ecause killed or inactivated pathogens can’t replicate at all, they can’t revert to a more virulent form

capable of causing disease as discussed above with live, attenuated vaccines!. 9owever, they tend toprovide a shorter length of protection than live vaccines, and are more likely to reuire boosters to createlong/term immunity. :illed or inactivated vaccines on the %.&. Recommended 'hildhood (mmuni)ation&chedule include the inactivated polio vaccine and the seasonal influen)a vaccine in shot form!.

Toxoids

&ome bacterial diseases are not directly caused by a bacterium itself, but by a toxin produced by thebacterium. 5ne example is tetanus; its symptoms are not caused by the Clostridium tetani bacterium, but bya neurotoxin it produces tetanospasmin!. (mmuni)ations for this type of pathogen can be made by



inactivating the toxin that causes disease symptoms. s with organisms or viruses used in killed orinactivated vaccines, this can be done via treatment with a chemical such as formalin, or by using heat orother methods.(mmuni)ations created using inactivated toxins are called toxoids. Toxoids can actually be considered killedor inactivated vaccines, but are sometimes given their own category to highlight the fact that they contain aninactivated toxin, and not an inactivated form of bacteria.Toxoid immuni)ations on the %.&. Recommended 'hildhood (mmuni)ation schedule include the tetanus and

diphtheria immuni)ations, which are available in a combined form.

Subunit and Conjugate Vaccines

8oth subunit and con#ugate vaccines contain only pieces of the pathogens they protect against.

&ubunit vaccines use only part of a target pathogen to provoke a response from the immune system. Thismay be done by isolating a specific protein from a pathogen and presenting it as an antigen on its own. Theacellular pertussis vaccine and influen)a vaccine in shot form! are examples of subunit vaccines.

nother type of subunit vaccine can be created via genetic engineering. gene coding for a vaccine proteinis inserted into another virus, or into producer cells in culture. 0hen the carrier virus reproduces, or whenthe producer cell metaboli)es, the vaccine protein is also created. The end result of this approach is arecombinant vaccine; the immune system will recogni)e the expressed protein and provide future protectionagainst the target virus. The 9epatitis 8 vaccine currently used in the %nited &tates is a recombinant

vaccine.

nother vaccine made using genetic engineering is the human papillomavirus 96V! vaccine. Two types of96V vaccine are available+one provides protection against two strains of 96V, the other four+but both aremade in the same way; for each strain, a single viral protein is isolated. 0hen these proteins are expressed,virus/like particles V$6s! are created. These V$6s contain no genetic material from the viruses and can’tcause illness, but prompt an immune response that provides future protection against 96V.

'on#ugate vaccines are somewhat similar to recombinant vaccines; they’re made using a combination of twodifferent components. 'on#ugate vaccines, however, are made using pieces from the coats of bacteria.These coats are chemically linked to a carrier protein, and the combination is used as a vaccine. 'on#ugatevaccines are used to create a more powerful, combined immune response; typically the 1piece2 of bacteriabeing presented would not generate a strong immune response on its own, while the carrier protein would.The piece of bacteria can’t cause illness, but combined with a carrier protein, it can generate immunity

against future infection. The vaccines currently in use for children against pneumococcal bacterial infectionsare made using this techniue.

Timeline ntr!" #$%&Attenuated 'easles Vaccine (eveloped

Centers for Disease Control and revention



)o! *it+ measles

*aurice 9illeman and colleagues developed an attenuated measles vaccine by passaging <ohn -nders’smeasles virus strain over =4 times through different cell types.

The resulting vaccine, Rubeovax, was given with a dose of gamma globulin antibodies to reduce reactionsmainly fever and rash!.

Timeline ntr!" -&.-#$/%0epatitis )" 1ecombinant Vaccine Licensed

Courtesy of Lorraine Hilleman'aurice 0illeman *atc+es as +is granddaug+ter receives t+e recombinant +epatitis ) vaccine in #$$$2

The 7D licensed *erck’s Recombivax 98. This hepatitis 8 vaccine was the first human vaccine producedby recombinant D> methods.

challenge in creating the vaccine involved avoiding the use of human blood products, as did *aurice

9illeman’s first hepatitis 8 vaccine. Therefore, *erck used an en)yme to remove the virus’s surface protein98sg, the ustralia antigen!. Researchers inserted the code for the antigen into yeast cells, whichproduced more of the surface protein. The yeast/derived surface protein produced immunity to the hepatitis8 virus.

different types of vaccines

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