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Employees at PoongLim Pharmatech in Gunsan, North Jeolla Province, produce low dead space (LDS) syringes on Feb. 18. (Yonhap News)

The South Korean government plans to allow an additional one or two people to receive COVID-19 inoculations per vial of vaccine — all thanks to special syringes developed by South Korean companies, which reduce the amount of vaccine discarded and allow for the use of leftover quantities.

At a Feb. 27 briefing, the government’s COVID-19 vaccination response team sent copies of an announcement to long-term care hospitals, public health centers and other vaccine administration sites nationwide informing them of its plans for using the residual vaccine.

Currently, COVID-19 vaccine vials contain enough for another person to receive an inoculation even after administration to the number of people recommended per vial. With the use of “low dead space” (LDS) syringes, this remaining vaccine can be given to other people instead of being thrown out.

In the cases of the AstraZeneca and Pfizer vaccines currently being given in South Korea, an ordinary syringe allows for 10 and five inoculations per vial, respectively. But with the special LDS syringes, the AstraZeneca vaccine can be administered to 11 or 12 people per vial, while the Pfizer vaccine can be given to six or seven.

LDS syringes are designed to leave almost no space between the piston and needle. For ordinary syringes, the standard residual volume in this space amounts to 0.07㎖ or less; for the LDS syringes, it is 0.035㎖ or less. This means the amount discarded can be cut in half.

The LDS syringes currently in use for vaccinations in South Korea are produced by Doowon Meditec, the Shina Corporation and PoongLim Pharmatech.

“Typically, a single vial [of vaccine] includes a certain extra amount in consideration of the losses that arise during administration,” explained Jung Gyeong-sil, director of the government team managing vaccination.

“In the case of the AstraZeneca vaccine, the rule is to have 5㎖ per vial, but it actually has a little extra, which means there could be a larger amount left over when you use a low dead space syringe,” she said.

To administer the Pfizer vaccine, a quantity of 0.45㎖ from the vial is mixed with 1.8㎖ of saline solution, for a total of 2.25㎖. The amount of vaccine administered per person is 0.3㎖.

But Jung stressed that the administration of residual vaccine is not an obligation, and that combining leftover vaccine from multiple vials was out of the question. Residual quantities may differ according to the type of syringe used and the nurse’s level of skill. For this reason, the government does not intend to alter its standard vaccination approach.

Experts shared a mixture of concern and anticipation.

“Dispensing beyond the set number of dispensations could increase the risk of contamination,” warned Eom Joong-sik, a professor of infectious disease at Gachon University Gil Medical Center.

“It’s important to administer a lot of vaccine, but it’s also crucial to do it safely,” he stressed.

In contrast, Ki Mo-ran, a professor of preventive medicine at the National Cancer Center, said, “We can’t afford to waste a single drop right now.”

“I don’t think we really need to worry much about infection, since the dispensations are taking place at a Clean Bench and the vials are cleaned with alcohol swabs,” she added.

Some observers predicted a key question would be how vaccine developers interpret the volumes obtained with the LDS syringes.

“Vaccine contracts are based on ‘dose’ units, and there’s a concern that the vaccine makers will look at those one to two extra doses and claim that those are included in the [contracted] volume that they supplied,” said Choi Won-seok, a professor of infectious disease at Korea University Ansan Hospital.

By Suh Hye-mi, staff reporter

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