Table of ContentsView AllTable of ContentsList of Live VaccinesMode of ActionVaccine TypesAdvantagesDisadvantagesContraindications
Table of ContentsView All
View All
Table of Contents
List of Live Vaccines
Mode of Action
Vaccine Types
Advantages
Disadvantages
Contraindications
A live virus vaccine contains a live, weakened (attenuated) virus that helps your body develop an immune response without you developing symptoms of the disease it is intended to prevent. Examples include the oral polio, MMR, chickenpox, and smallpox vaccine.
Thelive vaccinerelies on this weakened virus to “teach” yourimmune systemto recognize the specific disease-causingpathogenand launch a defensive attack if it encounters it again. Many vaccines of this type give you lifelong immunity with only one or two doses.
However, there are some cases when live virus vaccines are not advised. Immunocompromised patients, people who are pregnant, and those who are breastfeeding may want to hold off on getting certain vaccines.
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Examples of Live Viral Vaccines
Live attenuated vaccines have been among the most successful preventive interventions inmedical history. Due to global vaccination programs,smallpoxwas declared eradicated in 1980. Likewise,polioandmeasleshave been declared eliminated in some parts of the world.
There are also live attenuated vaccines used to prevent bacterial infections likecholera(bacterial disease of the small intestine),typhoid(bacterial infection spread through contaminated food), and tetanus (bacterial infection affecting the nerves).
How Live Attenuated Vaccines Work
An attenuated vaccine contains a weakened version of the virus or bacterium it’s meant to protect against. The version is usually too weak to cause illness, but strong enough to prompt the immune system to produceantibodiesagainst the full virus or bacterium.
Being exposed to the virus teaches the body how to fight the disease, preventing future infection. Sometimes the immune system needs to be exposed multiple times before it can fight off an invader.
As with other vaccines, you may need more than one dose to build up your immunity enough. For some diseases, you need a second shot within weeks or months of the first one. You may also need abooster shotevery year or a few years after your initial vaccination because immunity for some diseases wears off.
TheCOVID-19 vaccinedoes not contain a live virus. The vaccines used in the U.S. include two mRNA vaccines (Pfizer and Moderna) and one subunit vaccine (Novavax). These shots contain a gene from the COVID-19 virus, but not the whole live virus.
How Live Vaccines Differ
Live viral vaccines are just one type of vaccine. There are other types that do not involve live viruses or bacteria. These include:
There are benefits of using live attenuated vaccines that other vaccines may not deliver.
By and large, live vaccines are more durable, meaning that the body will retain its immune “memory” of a pathogen longer than it will with killed or subunit vaccines. Because of this, booster shots are not needed as often or at all with certain live vaccines. The live attenuated hepatitis A vaccine, for example, may protect you for 20 years or more.
Moreover, your immune system’s response to live vaccines is typically equivalent to that of anatural infectionwithout the associated harms. Most live vaccines can give you a lifetime of protection.
Additional research on using vaccines in this way is needed.
Tetanus, diphtheria, mumps, and polio are examples of diseases that were once common but are now rarely seen in the U.S. Even if eradication is not achieved, vaccines can significantly reduce the incidence and severity of many dreaded infections.However, theanti-vaccination movementthreatens to reverse many of those gains with diseases like measles.
One downside of live virus vaccines is that they require refrigeration, which can limit the ability to use them in resource-limited areas. If these vaccines are not kept at the correct temperature, they can become inactive. If this happens, immunization may not be effective.
Also, some live virus vaccines come as a powder and require reconstitution (restoring from a dry state) with a specific diluent (fluid) before they can be administered. Administrator error can also undermine the effectiveness of the vaccine.
Although small, there is the risk that the weakened live virus could end up causing the illness it was meant to prevent. Thesevaccine side effectscan affect people who are severelyimmunocompromised. In the absence of a normal immune response, the weakened virus has the potential to replicate and, in rare cases, reverse to its natural virulent state.
Who Should Not Get Live Vaccines?
As a general rule, live attenuated vaccines should not be given to severely immunocompromised people, including:
Even so, there are times when thebenefits of vaccinationin these individuals outweigh the risks. In such cases, expert consultation is needed to determine whether the use of a live attenuated vaccine is appropriate.
Live virus vaccines are generally safe for people who are breastfeeding. The two exceptions are the smallpox and yellow fever vaccine.
Immunization rates are often lower from inactivated vaccines compared to live ones. This is because multiple shots and booster shots are needed and people often don’t return to get them.
Summary
Live virus vaccines contain an attenuated (weakened) form of a virus that causes disease. Examples include the MMR, chickenpox, and smallpox vaccine. Live virus vaccines are different from inactivated vaccines in which the pathogen has been killed. Many other types of vaccines exist as well.
Vaccinesare one of the true public health success stories. They can reduce the number of people who get sick, the number of people who get severe disease, and, in some cases, eradicate diseases.
For protection against all types of pathogens, make sure you are up to date on yourimmunizations. If you’re not sure whether it’s time for a vaccine or booster, ask your healthcare provider.
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16 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Centers for Disease Control and Prevention.About the vaccine.Minor PD.Live attenuated vaccines: historical successes and current challenges.Virology. 2015;479-480:379-92. doi:10.1016/j.virol.2015.03.032World Health Organization.Vaccines and immunization: impact.Centers for Disease Control and Prevention.Explaining how vaccines work.Centers for Disease Control and Prevention.COVID-19 vaccine basics.U.S. Department of Health and Human Services.Vaccine types.World Health Organization.Inactivated whole-cell (killed antigen) vaccines.World Health Organization.Subunit vaccines.Centers for Disease Control and Prevention.About Hib vaccines.Zhang L.Hepatitis A vaccination.Hum Vaccin Immunother.2020;16(7):1565-73. doi:10.1080/21645515.2020.1769389Bulcha JT, Wang Y, Ma H, Tai PW, Gao G.Viral vector platforms within the gene therapy landscape.Sig Transduct Target Ther. 2021;6(1):53. doi:10.1038/s41392-021-00487-6Centers for Disease Control and Prevention.Altered immunocompetence.Pambudi NA, Sarifudin A, Gandidi IM, Romadhon R.Vaccine cold chain management and cold storage technology to address the challenges of vaccination programs.Energy Reports. 2022;8:955-972. doi:10.1016/j.egyr.2021.12.039Centers for Disease Control and Prevention.Contraindications and precautions.Centers for Disease Control and Prevention.Special situations.Lee Ventola C.Immunization in the United States: recommendations, barriers, and measures to improve compliance.P T.2016;41(7):426-36.
16 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Centers for Disease Control and Prevention.About the vaccine.Minor PD.Live attenuated vaccines: historical successes and current challenges.Virology. 2015;479-480:379-92. doi:10.1016/j.virol.2015.03.032World Health Organization.Vaccines and immunization: impact.Centers for Disease Control and Prevention.Explaining how vaccines work.Centers for Disease Control and Prevention.COVID-19 vaccine basics.U.S. Department of Health and Human Services.Vaccine types.World Health Organization.Inactivated whole-cell (killed antigen) vaccines.World Health Organization.Subunit vaccines.Centers for Disease Control and Prevention.About Hib vaccines.Zhang L.Hepatitis A vaccination.Hum Vaccin Immunother.2020;16(7):1565-73. doi:10.1080/21645515.2020.1769389Bulcha JT, Wang Y, Ma H, Tai PW, Gao G.Viral vector platforms within the gene therapy landscape.Sig Transduct Target Ther. 2021;6(1):53. doi:10.1038/s41392-021-00487-6Centers for Disease Control and Prevention.Altered immunocompetence.Pambudi NA, Sarifudin A, Gandidi IM, Romadhon R.Vaccine cold chain management and cold storage technology to address the challenges of vaccination programs.Energy Reports. 2022;8:955-972. doi:10.1016/j.egyr.2021.12.039Centers for Disease Control and Prevention.Contraindications and precautions.Centers for Disease Control and Prevention.Special situations.Lee Ventola C.Immunization in the United States: recommendations, barriers, and measures to improve compliance.P T.2016;41(7):426-36.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Centers for Disease Control and Prevention.About the vaccine.Minor PD.Live attenuated vaccines: historical successes and current challenges.Virology. 2015;479-480:379-92. doi:10.1016/j.virol.2015.03.032World Health Organization.Vaccines and immunization: impact.Centers for Disease Control and Prevention.Explaining how vaccines work.Centers for Disease Control and Prevention.COVID-19 vaccine basics.U.S. Department of Health and Human Services.Vaccine types.World Health Organization.Inactivated whole-cell (killed antigen) vaccines.World Health Organization.Subunit vaccines.Centers for Disease Control and Prevention.About Hib vaccines.Zhang L.Hepatitis A vaccination.Hum Vaccin Immunother.2020;16(7):1565-73. doi:10.1080/21645515.2020.1769389Bulcha JT, Wang Y, Ma H, Tai PW, Gao G.Viral vector platforms within the gene therapy landscape.Sig Transduct Target Ther. 2021;6(1):53. doi:10.1038/s41392-021-00487-6Centers for Disease Control and Prevention.Altered immunocompetence.Pambudi NA, Sarifudin A, Gandidi IM, Romadhon R.Vaccine cold chain management and cold storage technology to address the challenges of vaccination programs.Energy Reports. 2022;8:955-972. doi:10.1016/j.egyr.2021.12.039Centers for Disease Control and Prevention.Contraindications and precautions.Centers for Disease Control and Prevention.Special situations.Lee Ventola C.Immunization in the United States: recommendations, barriers, and measures to improve compliance.P T.2016;41(7):426-36.
Centers for Disease Control and Prevention.About the vaccine.
Minor PD.Live attenuated vaccines: historical successes and current challenges.Virology. 2015;479-480:379-92. doi:10.1016/j.virol.2015.03.032
World Health Organization.Vaccines and immunization: impact.
Centers for Disease Control and Prevention.Explaining how vaccines work.
Centers for Disease Control and Prevention.COVID-19 vaccine basics.
U.S. Department of Health and Human Services.Vaccine types.
World Health Organization.Inactivated whole-cell (killed antigen) vaccines.
World Health Organization.Subunit vaccines.
Centers for Disease Control and Prevention.About Hib vaccines.
Zhang L.Hepatitis A vaccination.Hum Vaccin Immunother.2020;16(7):1565-73. doi:10.1080/21645515.2020.1769389
Bulcha JT, Wang Y, Ma H, Tai PW, Gao G.Viral vector platforms within the gene therapy landscape.Sig Transduct Target Ther. 2021;6(1):53. doi:10.1038/s41392-021-00487-6
Centers for Disease Control and Prevention.Altered immunocompetence.
Pambudi NA, Sarifudin A, Gandidi IM, Romadhon R.Vaccine cold chain management and cold storage technology to address the challenges of vaccination programs.Energy Reports. 2022;8:955-972. doi:10.1016/j.egyr.2021.12.039
Centers for Disease Control and Prevention.Contraindications and precautions.
Centers for Disease Control and Prevention.Special situations.
Lee Ventola C.Immunization in the United States: recommendations, barriers, and measures to improve compliance.P T.2016;41(7):426-36.
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