Table of ContentsView AllTable of ContentsLive Vaccines and Viral SheddingLive vs. Killed VaccinesVaccine SheddingContraindicationsPrecautionsFrequently Asked Questions
Table of ContentsView All
View All
Table of Contents
Live Vaccines and Viral Shedding
Live vs. Killed Vaccines
Vaccine Shedding
Contraindications
Precautions
Frequently Asked Questions
Vaccinesstimulate your body to produce immunity against an infection. Those known as liveattenuatedvaccines use a very weak form of a virus (occasionally, bacteria) to achieve this.
Using them means that a modified form of the threat, which the vaccine is meant to target, does enter the body. This is done to spur animmune systemresponse, typically without causing illness.
Some people oppose live vaccine use because they think it can cause a virus to spread through a process called shedding. This article explains what that means and why there is little evidence to support this view.
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When a live vaccine is used to build immunity against a specific virus or otherpathogen, the body’s response is “virtually identical” to what you would see if you were naturally infected.
Live vaccines have saved lives. The process works against many threats, from chickenpox to cholera. But some people say that live vaccines can causeviral shedding.
Shedding is what happens when cells in a person’s body release viral particles. For example, the virus can go into the air. This may increase the risk of spreading the infection to others.
The risk of viral shedding is a top reason why some people holdanti-vaccination views. They say that the use of vaccines, especially live ones, is unsafe.
Recap
Live vs. Inactivated Vaccines
Live attenuated vaccines contain a weakened, mild form of a virus or bacteria. The vaccine is meant to stimulate an immune response in the form ofantibodies, a type of protein that fights off infection.
Live vaccines are meant to simulate a natural infection. They are thought to be better in doing so than the killed vaccines. Usually, they providelifelong protection with one or two doses.
Most killed vaccines need to be given with more than one dose for a complete vaccination. People also tend to needboostersyears later to keep the same level of immune protection. Yourtetanusvaccine, which uses inactivated tetanus toxin, is one common example.
Live attenuated vaccines have a long history of being safe and effective. People who areimmunocompromisedoften avoid live vaccines, though. This is due to a lower level of immune function that means they may get ill if one is given.
Live attenuated vaccines currently licensed in the United States include:
Two live attenuated vaccines commonly used in the past—a previous smallpox vaccine and the oralpoliovaccine (OPV)—are no longer used in the U.S.
Bacille Calmette-Guérin(BCG) for tuberculosis is a live vaccine rarely used in the U.S.BCG and Vivotif are used to prevent a bacterial infection. All others are used to prevent viral infections. The BCG vaccine is also sometimes used as a treatment forbladder cancer.
RecapBoth live vaccines and inactivated, or killed, vaccines are effective in causing the body’s immune system to respond to a target virus or bacteria. Live vaccines may be better at doing so because they are more like a natural infection. This makes the need for more than one dose, and boosters that come later, less likely.
Both live vaccines and inactivated, or killed, vaccines are effective in causing the body’s immune system to respond to a target virus or bacteria. Live vaccines may be better at doing so because they are more like a natural infection. This makes the need for more than one dose, and boosters that come later, less likely.
Top 20 Vaccines You Should Know About
It is true that viral shedding is one way of spreading a virus. Certain vaccines can, in fact, lead to such shedding. However, there is little evidence that viral or bacterial vaccines can lead to the level of shedding that would cause a vaccinated person to transmit the infection to others.
Viral shedding in and of itself does not translate to a higher risk of viral spread. It is only when the level of shed viruses is high that transmission can occur.
To date, the only vaccine with the potential to raise the risk of infection is the oral polio vaccine (OPV). It is no longer used in the U.S.
Moreover, the viral shedding from OPV was concentrated in the stool (feces). This makes any contact with them, such as thefecal-oralroute common with poor hygiene and hand washing, the primary way to cause such an infection.
There are few other documented cases of a virus that’s spread because of a vaccine. These are some highlights and takeaways from medical research:
Even so, viral shedding may pose risks to immunocompromised people when they have not been vaccinated against that specific virus. To this end, good hygiene may be the best defense. So is the routine practice of getting all the recommended vaccinations for adults and children.
RecapVaccine shedding is what those who hold anti-vaccination views are talking about when they say that a virus can be spread because a person got the vaccine for it. The theory is that this is due to the weak live virus in the vaccine. It’s true that this is possible, but it’s unlikely. A vaccine doesn’t cause enough viral shedding to reach a threshold for spreading the virus.
Vaccine shedding is what those who hold anti-vaccination views are talking about when they say that a virus can be spread because a person got the vaccine for it. The theory is that this is due to the weak live virus in the vaccine. It’s true that this is possible, but it’s unlikely. A vaccine doesn’t cause enough viral shedding to reach a threshold for spreading the virus.
Vaccines for Children: A Caregiver’s Guide
Live vaccines don’t cause disease. But they are made with weak forms of a virus or bacteria, and this means there is the risk that a person with a severely weakened immune system could get sick after getting one.
This is whyorgan transplant recipientstypically avoid live vaccines. Among others, this also is true for people who have chemotherapy treatments and for those living with an advanced stage of HIV.
Vaccines offer benefits that almost always outweigh the potential risks.With that said, there are several precautions to consider if you are scheduled to receive a live attenuated vaccine.
Among them:
Summary
A live attenuated vaccine contains a weak form of the live virus that it’s meant to protect against. This is to spur the body to mount its own immune response in defense. Both live vaccines and inactivated, or killed, vaccines work this way, but the live vaccines may be better because they behave more like a natural infection.
Some people oppose the use of live vaccines. They base part of their anti-vaccination stance on vaccine shedding, or the belief that the vaccines will actually spread the virus rather than control it. This is because the weak, live virus enters the body through the vaccine. Some of those who oppose vaccinations say the virus can then be shed and passed to others.
This may be true in theory but not in practice. Live vaccines don’t lead to shedding that causes high enough levels of the virus for it to spread, and therefore can’t really cause other infections.
A Word From Verywell
When it comes to approved vaccines, the greater health risk likely comes from not getting your recommended vaccinations at all. The return of measles, once eliminated in the U.S., makes the risk clear. Avoiding a vaccine can place you or your child at greater risk of infection and lead to outbreaks of vaccine-preventable diseases.
How to Discuss Vaccines With Vaccine Skeptics
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Frequently Asked QuestionsThe vaccine for COVID-19 is not a live virus, so it isn’t possible to shed the live coronavirus after getting the COVID shot. However, people who are vaccinated can still become infected with coronavirus. Once infected, it’s estimated that you would shed the virus for six to nine days after symptoms begin.Learn MoreGuide to COVID-19You should avoid close contact with immunocompromised people if you receive the oral polio vaccine (which is no longer administered in the United States).It’s believed that other vaccines, even those with live viruses, pose little risk. However, if you develop a rash with blisters after receiving the chickenpox vaccine, you should talk to a healthcare provider and may need to isolate yourself temporarily.Learn MoreUnderstanding Severe Combined ImmunodeficienciesVaccine shedding is when your body releases the components of a live vaccine after you were given the shot or oral dose.In theory, this could make a person who was vaccinated able to infect others. This is a concern for the oral polio vaccine that was discontinued in the United States, but it’s not believed to be a problem for other types of vaccines.Learn MoreGuide to Vaccines
The vaccine for COVID-19 is not a live virus, so it isn’t possible to shed the live coronavirus after getting the COVID shot. However, people who are vaccinated can still become infected with coronavirus. Once infected, it’s estimated that you would shed the virus for six to nine days after symptoms begin.Learn MoreGuide to COVID-19
The vaccine for COVID-19 is not a live virus, so it isn’t possible to shed the live coronavirus after getting the COVID shot. However, people who are vaccinated can still become infected with coronavirus. Once infected, it’s estimated that you would shed the virus for six to nine days after symptoms begin.
Learn MoreGuide to COVID-19
You should avoid close contact with immunocompromised people if you receive the oral polio vaccine (which is no longer administered in the United States).It’s believed that other vaccines, even those with live viruses, pose little risk. However, if you develop a rash with blisters after receiving the chickenpox vaccine, you should talk to a healthcare provider and may need to isolate yourself temporarily.Learn MoreUnderstanding Severe Combined Immunodeficiencies
You should avoid close contact with immunocompromised people if you receive the oral polio vaccine (which is no longer administered in the United States).It’s believed that other vaccines, even those with live viruses, pose little risk. However, if you develop a rash with blisters after receiving the chickenpox vaccine, you should talk to a healthcare provider and may need to isolate yourself temporarily.
Learn MoreUnderstanding Severe Combined Immunodeficiencies
Vaccine shedding is when your body releases the components of a live vaccine after you were given the shot or oral dose.In theory, this could make a person who was vaccinated able to infect others. This is a concern for the oral polio vaccine that was discontinued in the United States, but it’s not believed to be a problem for other types of vaccines.Learn MoreGuide to Vaccines
Vaccine shedding is when your body releases the components of a live vaccine after you were given the shot or oral dose.In theory, this could make a person who was vaccinated able to infect others. This is a concern for the oral polio vaccine that was discontinued in the United States, but it’s not believed to be a problem for other types of vaccines.
Learn MoreGuide to Vaccines
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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.
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