Don't worry, it's normal for the test to be in 2 steps. Usually, you are given a very small injection of te vaccination under the skin on your arm. If it leaves a mark (other than the possible bruising some people get from the needle) then you have natural immunity and don't need to have the actual vaccination. If like me, you're not immune already you then have to have the second part. We had to have it done when I started my nursing degree
You misunderstood. It is not a vaccine. It is a test to see if the person was ever infected with TB.
I've probably given about one thousand of them in my career as a nurse.
The test is called a Mantoux skin test for TB (Tuberculosis). It is also called a PPD test. PPD stands for purified protein derivative and the protein is a protein from the TB organism. It is not the whole TB Mycobacterium and can't cause or prevent TB. It is enough to cause a reaction if someone has been infected with TB in the past.
A small amount of the PPD solution is injected just under the top layers of skin. If it is given correctly, it will form a small bubble underneath the skin. This bubble will be absorbed in the next few hours and the bubble will go away. Occasionally, there will be some bruising if the needle nicked a small blood vessel.
If the person has had TB in the past, their immune system should react to the PPD and cause a reaction in the area 48 to 72 hours later at the area where the test was given. The area may have some redness, but the redness is ignored in reading the test. A positive test is shown by some 'thickening' under the skin, called induration, which would be measured to see if it is large enough to meet the definition of a positive test.
A positive test means that the person has been infected with TB at some time in the past. It doesn't tell when or whether the person had disease caused by TB. Most people who are infected with TB will not have TB disease (so will not become ill).
So, what is a 2 step TB test and why is it done?
Sometimes the immune system does not react to the TB skin test, even though the person had been infected with TB in the past. Reasons for this happening can include currently taking immunosuppressive drugs, having a condition that causes their immune system to not work correctly or having been infected with TB many years ago.
So, when the first test is given, there is no reaction, because the immune system doesn't 'remember' it has fought TB before.
But, the first test may 'remind' the immune system that it had previously reacted to TB and it reacts to the TB test by preparing to react the next time TB proteins show up in the body. This is called 'boosting'.
The 2nd step TB test takes advantage of this boosting. When someone has been infected with TB in the past, the second TB test will cause a reaction in most cases. If the second test is negative ( no significant reaction), there is very little chance that person has ever had TB.
Health care facilities give 2 step TB tests to people who either never had a TB test in the past or had their last TB test many years ago. This helps make sure that any infected people can be identified and evaluated to see if they need medication to prevent ever becoming ill with TB.
Why do they give TB tests to Health Care Workers?
There are 2 reasons.
The first reason is to make sure that the Health Care Workers are not infected to start with. if they are, they can be given preventative medicine to keep them from becoming ill.
The second reason would be to have a 'baseline' or beginning point. If the Health Care Worker cares for someone with TB illness, they can be tested again to see if they have become infected. If they have, they can be treated to prevent becoming ill.
So, is there a TB vaccine?
Yes. It is called BCG vaccine (Bacillus Calmette-Guérin). It is used in many areas of the world where TB is common because the risk of becoming infected and ill with TB is high in those areas.
It is NOT used in the US because TB is not very common and the risk of becoming infected with TB is generally low.
