Johnson & Johnson’s (NYSE:JNJ) chief scientific officer said today that the first doses of his company’s COVID-19 vaccine could be available for frontline healthcare workers in January or February, but added the company isn’t rushing it.

If granted an emergency use authorization by the FDA, that’s the earliest Dr. Paul Stoffels said the single-dose vaccine developed by J&J’s Janssen Pharmaceuticals could become available. After frontline workers, the elderly and those with comorbidities would be the next recipients, followed by the general population, Stoffels said during the virtual MedTech Conference by AdvaMed.

“It will be a massive logistic challenge to get vaccines to everyone in the world,” he said. “It will not be at once available for everyone.”

Stoffels echoed the Trump administration plan, unveiled in September, to distribute an eventual COVID-19 vaccine initially to targeted groups and more broadly as supply increases.

J&J’s work on developing vaccines for SARS, MERS, the Zika virus and HIV have all helped prepare it for the crush of developing, testing, producing and distributing a vaccine for COVID-19, according to Stoffels, who added that the company is not rushing its scientists.

“I have no pressure from anybody to get speed on a vaccine,” Stoffels said. “We do it because we can, but not because anybody tells us to go fast. We, the people of Johnson & Johnson, will never give a vaccine which we are not prepared to give to our own children, to our own families. That is how I look at it. We will not produce a vaccine which is not safe. That is not worth it.”

The Janssen vaccine candidate uses a human adenovirus called Adeno 26, to carry a small piece of DNA into a human to start producing a protein that generates antibodies to SARS-CoV-2, the virus that causes COVID-19 infection.

The phase 1 and 2 clinical trials for the vaccine each lasted six weeks, Stoffels noted. J&J sent the findings from those phases to the FDA incrementally so the agency could be prepared to act once it received each phase’s full report. J&J recently began enrolling 60,000 people in its phase 3 trial and plans to enroll 30,000 more.

“With 60,000 to 90,000 people experiencing that, we can study safety very well,” Stoffels said. “We’ll follow them long enough to make sure we know it, we’ll know what the benefits and the risks are, and then be very transparent. We’re going to show the population — from the moment we have the data, we’ll provide them and make sure people can join us in learning what we learn.”

Evaluating the vaccine candidate’s safety in such large numbers of people will take at least two to three months and investigators will follow some trial participants for five to six months. “It will give us a very good insight,” Stoffels said.

J&J started scaling up its production capabilities in May and already has the first batches of the vaccine candidate ready for filling vials. “Before the year end, we will start to have vaccines available in case… the study ends early, but most probably it will be January, February, and then we’ll have products available for distribution,” Stoffels said.

Each batch can generate up to 15 million doses, and the company estimates needing more than 300 million vials in the first year of distribution.

“There’s just not enough glass to put so many vaccines in vials,” Stoffels said. “That’s where a big part of the work is going to — fill and finish — getting the glass and then releasing that. We are ready to fulfill on our commitment of 1 billion vaccines next year.”

The company can keep the vaccine stable -20°C during shipment around the world, and healthcare providers can safely store it at normal refrigeration temperatures once it reaches its destinations, he added.

The U.S. government committed in August to pay J&J more than $1 billion for 100 million doses of the vaccine should it be authorized or approved by the FDA. The federal government agencies’ cooperation with drug companies during the vaccine development process has been unprecedented, according to Stoffels.

“We are just all normal human beings who want to solve this,” he said. “And we work together as teams across industry, the government and nongovernmental organizations to help out the world, because this needs to get to an end.”