Vaccinations could be made less painful by treating skin with a vaccine-laden liquid and using ultrasound to push it into the body
Vaccines can be delivered through the skin using ultrasound. This method doesn’t damage the skin and eliminates the need for painful needles. To create a needle-free vaccine, Darcy Dunn-Lawless at the University of Oxford and his colleagues mixed vaccine molecules with tiny, cup-shaped proteins. They then applied liquid mixture to the skin of mice and exposed it to ultrasound – like that used for sonograms – for about a minute and a half.
This is what I was thinking when reading the title. That one supposedly was cool, because there was no needle, never seen one in action but I presume there also was no bleeding.
Yet we don't see them used today, apparently the biggest reason was that there was a splashback and retrograde follow and then patient's blood could end up contaminating the nozzle, so basically it was like using the same needle on multiple patients.
They're not cool. They're fast and good for giving lots of shots in a situation where you need to get a lot of people in a hurry - especially if you're giving multiple vaccinations at the same time.
I got one of those used on me in basic training - a place where you need to vaccinate a few thousand people in about 30 minutes. Each one could do 4 shots at a time, and they had them in multiple configurations so you could get up to 4 in each arm for each "injection" station. We stepped through the line, and you got whatever shots you were missing in your records.
It hurts, like you could imagine a high pressure power washer with a needle-point burst with 4 heads blasting vaccines in your arms. It works, in the machine-like way the military works, and it is highly effective for mass vaccinations. So, I guess it makes it cool, but also it sucks like you'd expect 4-30 vaccines at once would suck.