CHICAGO — Public health officials have been debating whether it may be more effective to get more people their first dose of the COVID-19 vaccine and delaying the second round of shots that are needed for the highest immunity.

Last month, social media was flooded with images of frontline health care workers proudly rolling up their sleeves to get their first dose of the COVID-19 vaccine.

But a slow rollout, a surge in cases, and the emergence a of a new, more contagious strain of the coronavirus have increased the urgency of the vaccination campaign.

“I think there is an urgency to getting people vaccinated in the best way possible quickly,” said Dr. Benjamin Singer, an assistant professor pulmonary and critical care at Northwestern University’s Feinberg School of Medicine

In the UK, public health officials say prioritizing first doses will delay the interval of the second dose up to 12 weeks.

Pfizer, which is set to deliver 200 million doses of its vaccine to the U.S. by August of 2021, says it has tested their vaccine’s efficacy only when the two doses were administered 21 days apart. Moderna’s two-shot vaccine must be administered 28 days apart.

“Ninety, 95 percent efficacy, I mean, that's an amazing number, but the only way that we know with certainty to get to that level is with that two doses, three to four-week schedule,” said Singer.

Delays in administering the vaccine are already being reported across the U.S. There are now looming questions about what to do if a second dose has to be postponed.

“It could seem premature to begin discussing some of these contingency plans,” said Singer. “But I think it's an appropriate time to at least begin having the discussions.”

According to the Centers for Disease Control and Prevention (CDC), as of Monday morning, of the 15.4 million doses distributed, only 4.6 million people got their first dose.

“Right now, our problem isn't so much having the right number of doses, it's getting those doses into the arms of people,” said Singer.

In recent days, some health experts have suggested delaying the second dose could actually be a strategy to inoculate more people. In a Washington Post op-ed this weekend, Drs. Robert Wachter and Ashish Jha write: “Giving 100 million people — particularly those at high risk — a single shot that is 80 to 90 percent effective will save far more lives than giving 50 million people two shots that are 95 percent effective.”

“There's also some discussion about whether you could stay on the two-shot schedule but give a half dose inject you know half the volume and achieve somewhat of a similar response.”

But late Monday, in a strongly-worded statement, the FDA dismissed the idea of altering dosages and the timeline saying, “…making such changes that are not supported by adequate scientific evidence may ultimately be counterproductive to public health.”

The first doses of the vaccines in the U.S. were administered in mid-December, which means many are due for their booster shot this week.

DENVER, Colo. — Doctors are advising people to wait for U.S. government approval before attempting to receive a COVID-19 booster shot. But some are not waiting around and have managed to get a third shot.

Gina Welch lives in Maine. She said she has asthma as well as a liver condition and didn’t want to risk getting COVID-19.

"I felt I had to go take this extra step to protect myself. I don’t want to be one of the 15% of symptomatic cases and get a severe case of long COVID, and then have them say in six months, 'OK, we’re now going to do booster shots,'" Welch said.

Welch decided to go to a different clinic from where she got her first two vaccines and got a third dose.

"I was fully prepared for them to have a system with the CDC and then look me up when they entered my information and say, 'You already had your doses.' But there was nothing, and they gave me my first dose," Welch said.

Welch’s decision is similar to a trend being seen in multiple states.

Dr. Michelle Barron with UCHealth said if you don’t have a compromised immune system, getting a booster might not be necessary. For other groups, it’s important to speak with your doctor before making this decision.

"If you do end up doing this, that you are doing it under the right circumstances so you get the full benefit of the protection," Dr. Barron said.

Barron said studies have shown people with compromised immune systems could benefit from a booster, but until recommendations come out, it could be best to wait.

"There will always be those who say, 'You know, I am willing to take a risk' or 'I really want to do this anyway,' and know that this is not what we would recommend," Barron said.

For Welch, who received her third dose in June, it’s a decision she stands by.

"I feel much safer now in the situation, knowing that I am as protected as I can be," Welch said.

The Colorado Department of Public Health and Safety said, in part, “experts are trying to learn more about both natural immunity and vaccine-induced immunity of COVID-19 to determine if/when third doses are needed.”

As of Tuesday, booster shots aren’t officially recommended by the Advisory Committee of Immunization Practices.

This story was originally published by Ivan Rodriguez at KMGH.

The packing and shipping of a third COVID-19 vaccine approved for use in the U.S. is underway. Johnson & Johnson’s single-dose shot will start going into Americans’ arms in a matter of days.

Nearly 4 million doses are going out just this week. That's all of the current supply.

The number of doses states are getting is proportional to population, like with the Pfizer and Moderna vaccines.

Johnson & Johnson’s CEO says he's confident the company will be able to deliver on its promise of 100 million doses by June, and up to 1 billion by the end of the year.

“Johnson &Johnson built its vaccine from a virus that causes the common cold, known as adenovirus,” said Dr. Leo Nissola, a COVID Act Now medical advisor.

The science behind Johnson & Johnson's single-dose COVID-19 vaccine and the Moderna and Pfizer two-shot vaccines is different, but not new.

Johnson & Johnson’s vaccine takes a small amount of genetic material from the coronavirus and combines it with a weakened version of a common cold virus called adenovirus. That combination doesn't make us sick.

Adenovirus technology was also used to make Ebola and tuberculosis vaccines.

Pfizer and moderna use mRNA technology, which uses a genetic code to make the antigen protein specific to COVID-19. This code tells our body to make the antigen itself, prompting an immune response.

“The messenger RNA platform allows for scientists and drug makers to update the coding on these vaccines sooner, faster and at a different pace than adenovirus vectored vaccine, so in that sense, should we need a boost, our immune shot very likely will come from those mRNA based platforms,” said Dr. Nissola.

Pfizer and Moderna are already testing a third, booster shot to protect against COVID-19 variants.

Meanwhile, Johnson & Johnson may have the advantage of one and done for now, since it only requires a single dose. It can be stored for months in a refrigerator.

All three were found to be highly effective in preventing severe disease and death.

“It makes me hopeful that by summer, we will be able to vaccinate millions and millions of people and have a little bit more normalcy back,” said Dr. Nissola.

The J&J vaccine is also expected to boost vaccination equity since it's only one dose and is easier to store.