Another analogy is, NSA has find vaccine for Zika virus, but they haven't released it to public because as if now only they have weaponized it. If some rogue group manages to weaponize Zika, they release the vaccine. Though vaccinating whole world will take few years, US can do so in a matter of months. May cost millions of people in poor countries and 1000s in first world, that's just cost of business.
Unfortunately, for all 3 letter agencies of the world, the analogy may not be far fetched.
Bad analogy if you consider reality of Zika vaccine:
"Army is planning to grant exclusive rights to this potentially groundbreaking medicine–along with as much as $173 million in funding from the Department of Health and Human Services—to the French pharmaceutical corporation Sanofi Pasteur. "
A better analogy might be, the NSA knows that every other country in the world has weaponized a wide variety of viruses. The NSA has also weaponized and created vaccines for a wide variety of viruses. They know that they can't vaccinate the US population without tipping off the enemy to what they have. If they tip off the enemy to what they have, all their weaponized viruses become ineffective, and all of the sudden, the enemy is the only one with effective weaponized viruses.
Unfortunately, for all 3 letter agencies of the world, the analogy may not be far fetched.