Finnish nurse Sari Roos is teaching her colleagues a vaccination technique that enables her to squeeze more doses out of Covid-19 vaccine vials, helping to stretch scarce supplies and ensure more people can be inoculated.
Her air-bubble trick makes it possible to extract an elusive seventh dose from vials of the vaccine from Pfizer - one more than the six approved by Europe's health regulator that can normally only be drawn with a special needle and syringe.
Such "low-dead-space" shot utensils are in short supply, making Roos' trick all the more valuable as countries seek to protect people against new, more infectious coronavirus strains that are spreading a third wave of infection.
Roos' technique, similar to one used in Denmark, begins by drawing some vaccine liquid and then pushing it back into the bottle to get rid of air in the syringe. She then draws the exact dose and completes it with sterile air from the bottle.
The dose is then injected with minimal waste.
"The purpose of the air is to push all the liquid into the patient from the needle and close the injection channel so it won't bleed," Roos told Reuters at Helsinki's Laakso hospital where she works as a training nurse.
Her success has drawn the attention of colleagues at home and abroad who are keen to get more shots from each vial.
Tuija Kumpulainen, head of the health and safety unit at the Finnish Health Ministry, says drawing extra doses is safe when performed with precision.
"Skilled experts can get more doses but even they have to make sure no liquid is left in the equipment meaning the dose would be too small," Kumpulainen told Reuters.
While the technique is not easy and doesn't work every time, it also makes it possible to draw 12 doses from the 10-dose vials from AstraZeneca and Moderna - the other two shots approved for use in the European Union.
"The number of extra doses is significant," says Jutta Peltoniemi, an infectious diseases doctor in the city of Turku in southwest Finland.
"Imagine that you were among the extra people we vaccinated today in Helsinki who, without this technique, would have had to wait? These extra doses do save lives," Roos says.