The gun in that video shot vaccine through the skin at over 200 miles an hour, with no needle. One person could vaccinate up to a thousand people an hour. It was gentle enough to use on a sleeping baby without waking them.
It was called the jet injector. In a lot of countries it got a nickname: the peace gun.
Inside, a piston pushed liquid through a tiny hole at huge pressure, opening a pinprick in the skin and dropping the dose just underneath. An American engineer named Aaron Ismach built a foot-pump version so it could work in villages with no electricity, and he added a special tip that placed the smallpox vaccine in exactly the right layer of skin. Brazil ran one of the first big tests in 1965, which is probably why a Brazilian posted this clip.
Smallpox is the deadliest disease people have ever faced. It killed about 300 million people in the 20th century, and roughly one in three people who caught it died. In 1967, the year of this video, it was still infecting around 15 million people a year and killing two million of them.
The World Health Organization set out to wipe it out, and the jet injector was what made mass vaccination fast enough to win. Teams moved through whole countries, a thousand arms an hour. The last natural case was a hospital cook in Somalia, 1977. By 1980 smallpox was gone for good, the only human disease ever wiped off the planet, and over the years these guns had given out billions of shots against smallpox, measles, polio, and meningitis.
Then the same thing that made it work is what ended it. Firing liquid that hard flicked a thin film of blood back onto the tip, and that tip went straight into the next arm. Hepatitis B spreads on almost nothing, far less than a single drop of blood. At one California clinic in the mid-1980s, 31 people caught hepatitis B from a single shared injector. That was enough. The most common model was pulled from the market in 1997, and the US military, its biggest user, stopped using them on recruits that same year.
A cheap two-pronged needle, dipped and reused, finished the smallpox job the gun had started. The peace gun won the one war it was built for, then quietly retired.