Adam’s Journal, Part I
A few weeks ago, we wrote about a positive test for latent tuberculosis and treating that infection with antibiotics. On the heels of that column, we received some follow-up questions from readers. Here’s the first:
Once someone with a latent TB infection is treated, will they continue to test positive? For how long?
Susie Barry
Dr. Scofield Prescribes
Even following successful treatment for latent TB, most people will continue to test positive throughout their lives. But it’s nothing to worry about.
Both the skin and blood tests for TB don’t actually detect the bacteria that causes TB. Instead, they are looking for the body’s response to the infection.
So, even once the bacteria are vanquished, a person most likely will continue to test positive, as the immune system will still bear the hallmarks of the response that rid the body of TB. And that treatment will make the person less prone to developing active TB in the future.
Adam’s Journal, Part II
The second question:
People my age (nearing 80) were immunized against TB as children. Does that mean we are latent, home free, or something else?
Syd Logsdon
Dr. Scofield Further Prescribes
There is, indeed, a vaccine for TB. However, in the U.S., we have never had used it widely. I’ll explain why.
The vaccine, known as BCG, is what’s called a live vaccine. Rather than using deactivated bits of the virus, it uses weakened live bacteria found in cattle to stimulate the immune system.
Because the virus, though weakened, is still live, it can cause serious complications in people who are immunocompromised. For that reason, it’s almost never used in the U.S., and when it is, it’s only in children who are in continuous contact with someone who has untreated or drug-resistant TB.
Even if for some reason you did receive the BCG vaccine as a child, any immunity you had has almost certainly waned. Studies have shown this typically happens within 10 to 15 years of vaccination.
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Dr. Hal Scofield is a physician-scientist at the Oklahoma Medical Research Foundation, and he also serves as Associate Chief of Staff for Research at the Oklahoma City VA Medical Center. Adam Cohen is OMRF’s senior vice president and general counsel. Send your health questions to contact@omrf.org.
