#61 ·
Steven Castillo78 said:Hey there.
I've been wondering about that thing they do when you enter 7th grade—you know, that test where they prick your arm with a needle, inject some liquid, and then you have to wait a couple of days before they check the results.
I've got two quick questions regarding this.
1. What’s the actual name of that test?
2. How does the process work if you actually need the vaccination versus if you don't?
Cheers, hope I made sense and clearly explained what I'm looking for.
The answer is already covered in this thread, so I won't repeat it unnecessarily. Here it is:
granitebadger25 said:James Wilson15
Kids get their tuberculosis vaccinations right in the maternity ward... if the vaccine triggers an appropriate response, you'll just see a small scar left behind (check your right upper arm and you'll see the little vaccination scar).
In a vaccinated population like ours, the PPD test is relatively non-specific. For me personally, it doesn't always indicate actual exposure to infection, nor does it necessarily prove whether the vaccination was effective, even though people often interpret it that way. However, if PPD testing is performed regularly in such a population—as is standard for school-aged children—then a significant increase in the PPD reaction can be an indicator of exposure, though still not definitive proof of active infection.
The test is read by checking for swelling (not redness) at the injection site (on the inner side of the right forearm) 72 hours after the PPD is administered.
0-4 mm = negative reaction
5-15 mm = positive reaction
> 15 mm = hyper-reactor
A negative reaction, even with a visible BCG scar on the arm, does not mean the vaccination failed, although pediatricians frequently re-vaccinate those kids just to be safe. A negative reaction often occurs following a minor viral infection and might simply reflect an individual's cytokine profile.
A positive reaction is most common in a vaccinated population like ours, and it is considered normal (which is the case with your children).
For hyper-reactors—especially those who have transitioned into this category since their last PPD test—additional testing is required. This shift suggests the possibility that these children were exposed to the tuberculosis bacillus in the interim.
One quick addition: the protocol generally calls for vaccinating "non-reactors" (those students with a negative reaction, specifically under 5 mm) during the 7th grade.
