BALLABGARH, India — In late November, an urgent email popped up in the inbox of Hindustan Syringes & Medical Devices, one of the world’s largest syringe makers.

It was from UNICEF, the United Nations agency for children, and it was desperately seeking syringes. Not just any would do. These syringes must be smaller than usual. They had to break if used a second time, to prevent spreading disease through accidental recycling.

Most important, UNICEF needed them in vast quantities. Now.

“I thought, ‘No issues,’” said Rajiv Nath, the company’s managing director, who has sunk millions of dollars into preparing his syringe factories for the vaccination onslaught. “We could deliver it possibly faster than anybody else.”

As countries jostle to secure enough vaccine doses to put an end to the Covid-19 outbreak, a second scramble is unfolding for syringes. Vaccines aren’t all that useful if health care professionals lack a way to inject them into people.

will spend $1.2 billion over four years to expand capacity in part to deal with pandemics.

The United States is the world’s largest syringe supplier by sales, according to Fitch Solutions, a research firm. The United States and China are neck and neck in exports, with combined annual shipments worth $1.7 billion. While India is a small player globally, with only $32 million in exports in 2019, Mr. Nath of Hindustan Syringes sees a big opportunity.

Each of his syringes sells for only three cents, but his total investment is considerable. He invested nearly $15 million to mass-produce specialty syringes, equal to roughly one-sixth of his annual sales, before purchase orders were even in sight. In May, he ordered new molds from suppliers in Italy, Germany and Japan to make a variety of barrels and plungers for his syringes.

cleared Pfizer’s vaccine for emergency use, Robert Matthews, a UNICEF contract manager in Copenhagen, and his team needed to find a manufacturer that could produce millions of syringes.

“We went, ‘Oh, dear!’” said Mr. Matthews, as they looked for a syringe that would meet W.H.O. specifications and was compact for shipping. Hindustan Syringes’ product, he said, was the first.

The company is set to begin shipping 3.2 million of those syringes soon, UNICEF said, provided they clear another quality check.

Mr. Nath has sold 15 million syringes to the Japanese government, he said, and over 400 million to India for its Covid-19 inoculation drive, one of the largest in the world. More are in line, including UNICEF, for which he has offered to produce about 240 million more, and Brazil, he said.

Marc Koska, a British inventor of safety injections, and its ability to produce all of the components in-house. Hindustan Syringes makes its needles from stainless steel strips imported from Japan. The strips are curled into cylinders and welded at the seam, then stretched and cut into fine capillary tubes, which machines glue to plastic hubs. To make the jabs less painful, they are dipped in a silicone solution.

The syringe business is a “bloodsucker,” Mr. Nath said, where upfront costs are astronomical and profits marginal. If demand for his syringes drop by even half in the next few years, he will lose almost all of the $15 million he invested.

It’s clearly a frugal operation. The blue carpet in Mr. Nath’s office looks just as old as his desk or the glass chandelier by the stairs, fixtures his father put in place in 1984, before he handed over the company to Mr. Nath and his family.

A family business is exactly how he likes it. No shareholders, no interference, no worries. In 1995, when Mr. Nath needed money to increase production and buy lots of new machines, he sought private capital for the first time. Had that been the case today, he said, he wouldn’t be able to follow his gut and produce his syringes at this enormous scale.

“You have a good night’s sleep,” Mr. Nath said. “It’s better to be a big fish in a small pond.”