It was only a month ago that the first thousands of doses of the COVID-19 vaccine arrived in the Centennial State. Since that “absolutely historic” day, more than 223,000 Coloradans have already received the Pfizer and Moderna vaccines—and many are already onto their second dose (or booster shot) of the vaccination.

While the vaccines have undoubtedly brought hope that the end of the pandemic and a return to normalcy is coming, there’s been confusion on how the distribution process will roll out locally. Some Coloradans are also still concerned about possible side effects. As Colorado moves into phase 1B of the distribution plan, we spoke to Dr. Richard Zane, chief innovation officer for UCHealth and chair of emergency medicine at the University of Colorado School of Medicine, to understand more about how the vaccines work and when Coloradans can expect to receive them.

Moderna or Pfizer: What’s the difference?

“The Pfizer and the Moderna vaccines are substantively similar to each other that nobody should really pick one or the other,” says Dr. Zane, whose research background is in mass casualty care and disaster response. Both vaccines require a booster shot, with the Pfizer vaccine requiring a second dose 21 days after the first dose and Moderna 28 days after the initial shot. According to experts, availability and location are the two main variables in determining which vaccine you will receive.

How the Vaccine Works

“I view this vaccine as one of the single most important achievements in our generation in medicine and science,” Dr. Zane says. Both the Moderna and the Pfizer vaccines are messenger RNA vaccines, or mRNA vaccines, which is different from any other vaccine ever made. Typical vaccines “put a weakened or inactivated germ into our bodies,” so the body can create antibodies to fight the virus, Zane says. MRNA vaccines, however, act as a communication device, telling the cells in the muscle how to create a protein that looks like COVID-19. “Your body becomes a vaccine factory,” Dr. Zane says. “And it makes its own antigen which then stimulates the body to make antibodies, which then transfers into immunity.”

Immunity, or resistance to COVID-19, is expected after both doses have been administered. “It’s thought that that level of immunity is somewhere in the 50 to 70 percent range after the single dose,” Dr. Zane says. “Then, a week to 10 days after the booster [shot], you have 95 percent or so immunity.” Experts hope to reach herd immunity, also known as community immunity, when most of the population has been vaccinated (or naturally infected).

(MORE: When Will  Colorado’s COVID-19 Epidemic Be Over?)

What Are the Side Effects?

Both the Moderna and Pfizer vaccines are shown to have similar side effects, many of which are also symptoms of COVID-19. Fever, chills, muscle aches, and headache are the most reported side effects, and are common after the second dose. Dr. Zane maintains that most of these side effects are normal and can be treated with an over-the-counter pain reliever and should go away within a few hours. “These side effects are due to interferon, or the immune response,” Dr. Zane says.

The Most Common Misconceptions About the Vaccine

Dr. Zane says he’s heard it all—from general concern and confusion to conspiracy theories—but the most common misconception about the vaccine, he says, is that it was somehow rushed and made too quickly. “That’s not even a little bit true,” Dr. Zane says. “The reality is that the vaccine was expedited,” which means that an enormous amount of resources (money and scientific research) went into developing the vaccine as the result of Operation Warp Speed—a collective effort spearheaded by the U.S. government to produce and deliver 300 million doses of COVID-19 vaccine to the public. (Each week, the federal government informs Colorado Department of Public Health and Environment (CDPHE) on the exact number of vaccines Colorado will receive for the following week.)

One oft-repeated concern about the vaccines is that they could cause infertility. “This is absolutely unequivocally baseless,” Dr. Zane says. “There is no evidence, anywhere, under any circumstances that it is in any way affiliated with or associated with infertility.” According to the CDPHE, researchers will continue to learn more about rare side effects over the next year.

Unlike typical vaccines like the flu shot, which delivers a small dose of the flu into the body to trigger an immune response, the mRNA vaccine doesn’t use the live virus that causes coronavirus. This means that the vaccine doesn’t actually give someone COVID-19. Dr. Zane, however, still encourages people to wear a mask and practice social distancing even after getting vaccinated. “What we don’t know is how much antibody you have circulating in different parts of your body,” he says. “We’re assuming that people can be infectious without being symptomatic and still be carriers and spreaders of COVID-19 despite vaccination…which is why there’s still the recommendation to wear a mask until such time as a significant proportion of the population have been vaccinated.” This is the biggest limitation to going back to having even semblance of normal life, he says.

When Will It Be My Turn?

Image courtesy of the Colorado Department of Public Health & Environment

Colorado’s COVID-19 vaccine distribution plan is broken up into four phases: 1A, 1B, 2, and 3. The Centennial State is currently in phase 1A and 1B of the plan, with the state aiming to vaccinate 70 percent of Coloradans 70 years and older by the end of February. Those who qualify can contact their local healthcare provider to find out how to get the vaccine or visit CDPHE to learn more. In phase 1B, an estimated 1,315,000 Coloradans will be eligible to receive the vaccine including: frontline essential workers, teachers, and government officials. Higher risk individuals will receive the vaccine during phase 2 of the plan, which will begin as early as March 1. The rest of Colorado’s population is expected to receive the vaccine by the summer. Additionally, the state is not requiring Coloradans to show government identification in order to receive the vaccine—ensuring that no one is excluded from getting vaccinated.

“I think Colorado is doing a pretty phenomenal job,” Dr. Zane says. Right now, Colorado is expecting to receive about 70,000 vaccines each week through the end of January. “Our single limitation, and it’s a big limitation, is supply of vaccines from the federal government.” While Colorado’s vaccine supply is at the mercy of the federal government, changes to the vaccine distribution and availability are expected to take place under the Biden Administration. According to his team, President-elect Joe Biden—who takes office next week—plans to build up the country’s vaccine supply by invoking the Defense Production Act, if needed. In his newly proposed $1.9 trillion spending package, Biden plans to get “100 million COVID vaccine shots into the arms of the American people” within his first 100 days in office.

Until the rest of the population is vaccinated, Coloradans are expected to keep sporting masks, practice social distancing, and look out for one another. “I want to tell people that the decision to get a vaccine is not just about your own health, but it’s also a societal responsibility,” Dr. Zane says. “It’s not just about you and your family; it’s about the rest of society.”

Victoria Carodine
Victoria Carodine
Victoria Carodine is a Denver-based writer and a former editor on 5280's digital team.