In the race to get people immunized in the U.S., pharmacists made a key discovery — that vials of Pfizer Inc.’s COVID-19 vaccine contain an extra dose. Extracting that extra bit of vaccine, however, hinges upon the availability of a specialized syringe that is in short supply.

When a medication or vaccine is injected, some amount of it can linger in the syringe in what’s known as the “dead space” between the plunger and needle. Low-dead space syringes are designed to minimize that, and with it, waste. That makes them a crucial tool in extracting six doses, instead of the five that were expected, from each Pfizer vial.

The pressing need for low-dead space syringes is relatively new. The specialized syringes are considered a niche product, used when dealing with drugs like fertility treatments, where medication waste can be especially costly.

In an early plan, the Biden administration described dead-space syringes and needles as one of 12 supply shortfalls it planned to address. Yet it is not as easy as flipping a switch and the vaccination campaign is trying to outpace faster-spreading Covid variants.

“If you’ve got fires burning, every drop of water matters so you have to use as much as you can as quickly as you can and strategically,” said Bruce Gellin, former director of the National Vaccine Program Office in the Department of Health and Human Services.

The syringe issue is one of several officials are addressing to ensure no drop of limited vaccine is wasted as states continue to criticize the government for a lack of supply. Since President Joe Biden took office Jan. 20, federal agencies have issued guidance that allows people to get follow-up shots a few weeks later than the recommended interval if needed, and says that in “exceptional circumstances” it’s okay to mix and match doses.

These steps provide a window into efforts to push along the country’s complex and high-stakes vaccine effort. It is occurring amid staggering logistical complexities and supply shortages as well as the threat of renewed spread from the variants.

Another approach to deploy shots in arms faster is to focus on first doses, as the U.K. is doing. However, that risks giving people less protection and could inadvertently promote the emergence of variants, Anthony Fauci, the nation’s top infectious diseases expert, said at a White House briefing Monday.

Supply Focus

Low-dead space syringes have gained the spotlight against a backdrop of shortages of COVID-19 vaccines, a key constraint throughout the U.S. immunization push to date.

“The biggest challenge I’m hearing from states right now is simply a lack of supply,” said Representative Diana DeGette, a Colorado Democrat who chairs the House Energy and Commerce Committee’s oversight panel, which held a hearing last week with state officials on boosting vaccine distribution. “They stand ready to vaccinate many more Americans if we just get them the doses they need.”

Andy Slavitt, a senior adviser to the White House’s COVID-19 effort, said at a briefing last week that about 80% of Pfizer kits contain low-dead space syringes, while the rest contain other syringe types that could be used to extract the sixth dose. Asked for comment on Monday, the White House referred to Slavitt’s remarks.

In reality, it’s unclear just how available those syringes are.

Hospitals and others that are part of Premier Inc., a group-purchasing organization, are looking to obtain more low-dead space syringes, “so we know they’re not getting everything that they need,” said Jessica Daley, a pharmacist and vice president of strategic supplier engagement at Premier. The group is collecting information about what’s included in Operation Warp Speed kits from the more than 4,100 acute care hospitals and facilities across the country that are its members.

Government Kits

About 85% of syringes in government-provided kits are low-dead space ones, said Mark Jarrett, chief quality officer for Northwell Health. The remainder are larger syringes with longer needles to vaccinate patients who are larger physicially, he said.

Yet Northwell is currently focused on vaccinating the elderly, who generally don’t require the larger syringes. Jarrett said he would prefer to have kits fully composed of low-dead space syringes, to extract more doses. Northwell is extracting six doses of 10-15% of vials, he said.

“Right now we get low-dead space syringes from the federal government, but not enough for everybody,” Jarrett said. “We have ordered the low volume ones but everyone else is ordering them at the same time. There is a national shortage.”

Most suppliers are limiting providers to an allocation based on their purchasing patterns, meaning securing extra supply of low-dead space syringes for COVID-19 vaccination efforts can be difficult, Premier’s Daley said.

Becton Dickinson and Co., the world’s largest needle and syringe manufacturer, contracted with the U.S. government to deliver 286 million needles and syringes for the vaccination push, including 40 million low-dead space syringes. Yet because demand for the devices has historically been much lower, “we have limited production capacity,” said Troy Kirkpatrick, senior director of public relations.

“Initially when we were having conversations with the government, low-dead space is not something that was talked about as needing to prioritize,” Kirkpatrick said. “This extra dose came up at the end of the discussion, not the beginning.”

The Biden administration has taken steps to ramp up vaccine distribution, saying Tuesday that it will boost weekly vaccine doses to states to 11 million Pfizer-Inc-BioNTech SE and Moderna Inc. shots. Both vaccines require two doses several weeks apart.

Follow-Up Doses

While extracting more doses per vial will help boost supply, the Biden administration also has been trying to sort out what advice to give about the second shot.

The day after Biden took office last month, the Centers for Disease Control and Prevention issued guidance saying the follow-up dose of the messenger RNA-based Pfizer and Moderna vaccines could be given up to six weeks after the initial shot and that the vaccines could be mixed if absolutely necessary. The recommended intervals that were studied in clinical trials are three weeks for Pfizer’s shot and four weeks for Moderna’s. The Food and Drug Administration also offered support for “modest delays.”

Just two weeks earlier FDA leadership had issued a statement saying extending the time between doses hadn’t been studied and could put “public health at risk.”

The FDA declined to provide data it may have consulted in issuing the guidance. Kristen Nordlund, a spokeswoman for the CDC, said Pfizer’s clinical trial on its vaccine included people who received their second dose up to 42 days after the first. Receiving a vaccine made by a different company for a second dose hasn’t been studied.

Jay Butler, deputy director for infectious diseases at the CDC, described the changes as pragmatic responses to real-world circumstances. Interchanging doses is better than restarting the vaccine series from the start, especially as “we really have no data at all on the safety of three doses,” Butler said, speaking at a briefing last month hosted by the Infectious Diseases Society of America.