Vaccinesstimulate your body to produce immunity against an infection.
This is done to spur animmune systemresponse, typically without causing illness.
This article explains what that means and why there is little evidence to support this view.
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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.
Get our printable guide for your next doctor’s appointment to help you ask the right questions.
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.
This leads a healthy body’s immune system to respond as intended.
Some people oppose their use due to a risk of infection from viral shedding.
This risk exists in theory but there is little evidence that it poses a real public health threat.
The live vaccines stand in contrast to vaccines that use dead bacteria or viruses.
These inactivated, or killed, vaccines are still recognized by the immune system as harmful.
So they lead to the same antibody response.
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.
All others are used to prevent viral infections.
The BCG vaccine is also sometimes used as a treatment forbladder cancer.
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.
They say the shedding is resulting from a vaccine that puts the virus itself into public circulation.
Thus, the use of vaccinesespecially live attenuated vaccineswould promote the spread of infection.
It is true that viral shedding is one way of spreading a virus.
Certain vaccines can, in fact, lead to such shedding.
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.
It is no longer used in the U.S.
Moreover, the viral shedding from OPV was concentrated in the stool (feces).
There are few other documented cases of a virus that’s spread because of a vaccine.
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.
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.
Contraindications
Live vaccines don’t cause disease.
This is whyorgan transplant recipientstypically avoid live vaccines.
The benefits and risks must be weighed on a case-by-case basis.
But this depends on their immune status, measured by theCD4 T-cell count.
This is to spur the body to mount its own immune response in defense.
Some people oppose the use of live vaccines.
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.
The return of measles, once eliminated in the U.S., makes the risk clear.
Get our printable guide for your next doctor’s appointment to help you ask the right questions.
However, people who are vaccinated can still become infected with coronavirus.
Once infected, its estimated that you would shed the virus for six to nine days after symptoms begin.
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