The heavy snow that blanketed the Omaha area Tuesday morning was not enough to deter volunteers from traveling to the University of Nebraska Medical Center to enroll in a new clinical trial to test the safety and effectiveness of another vaccine candidate for COVID-19.

The university and its clinical partner, Nebraska Medicine, plan to enroll up to 1,000 people in the study of the vaccine developed by the Maryland biotech firm Novavax Inc. The trial, which began Monday in the United States and Mexico, seeks to enlist a total of 30,000 people.

Dr. Diana Florescu, who is leading the Phase 3 trial at UNMC, said there already has been a lot of interest in the trial — so much so that the university is adding appointments on the morning of Dec. 31.

The researchers are hearing from two groups of patients: Those who know they won’t otherwise get a vaccine for months and are willing to take the chance on receiving it early through the trial; and those who want to avoid the side effects they’ve heard may occur with the two vaccines already rolling out to health care workers and emergency responders.

She’s also heard another “amazing” reason for why volunteers are coming out in the snow: At a time when the pandemic is weighing heavy, people see new vaccines as a way to reduce illness and return to a more normal life.

“Everybody wants to help to bring more vaccines to the market so everybody can get vaccinated faster,” said Florescu, a professor and infectious diseases specialist in UNMC’s internal medicine department. “People want to help.”

UNMC is among about 115 trial sites for the Novavax vaccine. For this trial, the medical center is working with the COVID-19 Prevention Network formed by the National Institute of Allergy and Infectious Diseases and the National Institutes of Health to respond to the pandemic.

“Our hope is that this vaccine will prevent people from developing severe disease and decrease the chances of being hospitalized or dying,” Florescu said.

The trial launches as the two other vaccines — one made by Pfizer and BioNTech and the other by Moderna Inc. — already are being dispensed to Nebraska health care providers and emergency responders.

As of Monday morning, 21,419 first doses of the vaccines had been administered in the state, according to the Nebraska Department of Health and Human Services. A total of 49,390 doses had arrived and been distributed to Nebraska health care facilities.

Vaccination of staff and residents of long-term care facilities was slated to begin this week. As of Monday, facilities had scheduled more than 130 vaccination clinics for the coming weeks, state officials said.

Health officials say more vaccines from more vaccine-makers will be critical to producing enough shots to vaccinate as many in the United States and abroad as are willing to take them. While new coronavirus cases and hospitalizations in Nebraska and neighboring states have decreased in recent weeks, they have surged in other parts of the country.

“If you want to have enough vaccine to vaccinate all the people in the United States who you’d like to vaccinate — up to 85% or more of the population — you’re going to need more than two companies,” Dr. Anthony Fauci, the NIAID’s director, told the Associated Press on Monday.

The Novavax vaccine is the fifth to reach final-stage testing in the United States, the AP reported.

Omaha-based Meridian Clinical Research, which provided Nebraska research sites for the Pfizer and Moderna vaccines, also has been seeking volunteers for the Novavax trial and for a Phase 2/3 trial of a candidate by Medicago.

The Novavax vaccine is made differently from the Pfizer and Moderna vaccines, relying on injections of harmless copies of the spike protein found on the coronavirus’s surface to stimulate an immune response to the virus. The vaccine also includes a component, called an adjuvant, to boost the response and stimulate higher levels of antibodies.

The Pfizer and Moderna vaccines use a newer technology that involves injecting a piece of messenger RNA that codes for the spike protein. The mRNA induces the body to make enough of the protein to stimulate the immune system. The mRNA does not enter our cells’ nuclei, where our genetic material, DNA, resides.

Earlier studies of the Novavax vaccine, according to the company, demonstrated that the candidate “provoked a robust immune response.” And, it can be stored at refrigerator temperatures, unlike the vaccines now in use.

Like the other two vaccines, the candidate requires two shots given roughly three weeks apart. For the study, two of every three people who participate will get the vaccine and one of every three will get a dummy shot.

Florescu encouraged people who won’t get the Pfizer or Moderna vaccines in the next three to six months to consider enrolling in the trial. Participants in the Novavax trial can stay enrolled and also receive the Pfizer or Moderna vaccine when it becomes available to them.

However, she cautioned that people who get vaccinated or enroll in a trial still will have to take precautions, including wearing masks and socially distancing.

Those who get the vaccine might not develop symptoms but they could be asymptomatic carriers and spread it to others. And while the Pfizer and Moderna vaccines were more than 90% effective, no vaccine is 100% effective, meaning that they could still get the illness.

For the trial, researchers are looking for people who are:

Ages 19 and older, including those over 65 and those with chronic or long-term health conditions.

Have not had COVID-19.

Are not pregnant or breastfeeding or planning to become pregnant during the next four months.

Are at increased risk for exposure to infection with COVID-19, including those who work in essential jobs and those with underlying health conditions.

For more information or to enroll, visit unmc.edu/covidvaccinetrial and complete a questionnaire. A study team member will contact those who apply to discuss possible enrollment.

Our best Omaha staff photos of 2020