After months of trials, the first coronavirus vaccines are expected to be approved by the federal government in the coming days. Gov. Tim Walz on Tuesday laid out the initial steps in Minnesota’s vaccination plan, with the earliest doses likely to arrive as soon as next week. Here are answers to questions you may have about vaccines and the state’s strategy to vaccinate millions of Minnesotans. 

Which are the most promising coronavirus vaccine candidates right now?

While more than 50 vaccine candidates have progressed to clinical trials with humans, two front-runners have emerged. A vaccine developed by Pfizer and BioNTech is first in line for review by the U.S. Food and Drug Administration this month, and another produced by Moderna will be considered a week later. A third vaccine developed by the University of Oxford and AstraZeneca could be ready for review in early 2021.

How will they work?

The Pfizer/BioNTech and Moderna vaccines use messenger RNA to instruct cells to create a harmless piece of the virus that causes COVID-19. This piece of “spike protein” is a key feature of the virus (you’ve likely seen COVID-19 depicted as a spiky ball). The body recognizes this spike protein as foreign and triggers an immune response to fend off future infection.

AstraZeneca’s is a viral vector vaccine and uses the adenovirus — a strain of the common cold found in chimpanzees — to deliver a piece of that spike protein into cells. This prompts an immune response to inoculate the recipient against infection.

What are some of the differences between the vaccines?

Both the Pfizer and Moderna vaccines must be frozen for transportation and storage. Pfizer’s vaccine is the most demanding, needing a storage temperature of -70 degrees Fahrenheit, which requires specialized freezers. Moderna has said its vaccine can be kept stable at around -20 degrees Fahrenheit for up to six months, closer to the temperature of a standard freezer.

AstraZeneca’s vaccine only needs to be refrigerated at between 2 and 8 degrees Fahrenheit, making its distribution less complicated and less expensive. AstraZeneca’s vaccine is also significantly cheaper to manufacture, at roughly $3-$4 per dose.

How safe are they?

The first phase in any clinical trial is dedicated to making sure a drug is safe. Vaccines cannot be approved without passing this crucial step. According to the CDC, a clinical trial is paused whenever an “unexpected health event” is detected so that researchers can investigate any potential safety concerns. Minnesota health officials have said that they have confidence in the clinical trials conducted and the regulatory approval process so far.

The vaccines have been tested in tens of thousands of volunteers so far, and serious side effects have not been reported. Health officials will be monitoring for side effects as more people get vaccinated, as well as for any potential longer-term issues.

Dr. Anthony Fauci, the nation’s top infectious disease expert, has noted that people might feel achy or feverish right after the shot, or some soreness in the arm. Other temporary side effects reported by study participants included fatigue, headache and chills.

How effective are the vaccines?

Pfizer and Moderna have both reported that their vaccines reached 95% efficacy in clinical trials, far exceeding scientists’ expectations. According to Fauci, the goal was to reach 75% efficacy with any COVID-19 vaccine, and the FDA said it would approve a vaccine with just 50% efficacy.

AstraZeneca has reported 62% efficacy with its vaccine, though that rate appears to jump to 90% when administered with a stair-step dosage. Participants were given a half-dose for the first round of immunization followed by a full dose, and researchers noted the vaccine was more effective.

When could vaccines become available?

No vaccine has been officially approved yet. The FDA is set to review the Pfizer vaccine on Dec. 10 and the Moderna vaccine on Dec. 17. Once a vaccine is approved for emergency use, the first doses are expected to begin shipping within days. States were required to place orders for the initial round of vaccines by Dec. 4.

The vaccines could begin arriving in Minnesota the week of Dec. 14, according to health officials. They will be shipped to 25 “hub” medical facilities around the state. From there, they will be distributed to 118 smaller clinics, or “spokes,” that will make doses available to providers.

Officials currently expect 183,400 doses — 46,800 from Pfizer and 136,600 from Moderna — to arrive in the first month. Vaccinations could begin the week of Dec. 21. Additional vaccines are expected to be approved in the coming months.  Minnesota Health Commissioner Jan Malcolm cautioned that it could be six months before vaccines become widely available.

On Dec. 2, Britain approved the Pfizer vaccine for emergency use, becoming the first nation in the world to authorize a coronavirus vaccine. The U.K. began dispensing the first vaccines to patients on Dec. 7.

Who will have first access to vaccines?

A CDC advisory panel voted Dec. 1 to recommend that health care workers and nursing home patients — about 24 million Americans, or roughly 7% of the U.S. population — should be prioritized for access to the first vaccine doses. The panel will meet again in the future to decide which groups should be next in line.

In Minnesota, first priority will be given to front-line health care workers in COVID-19 hospital units, emergency departments and nursing homes along with paramedics, COVID-19 testing personnel and some public health workers. Residents in nursing homes will also be in the highest priority group.

In later phases, essential workers and adults with high-risk medical conditions and those 65 or older are expected to be prioritized for vaccination.

How will the vaccines be administered?

All three vaccines will require two doses, delivered via injection. The Pfizer vaccine will require a booster shot three weeks after the first dose, while the Moderna vaccine’s booster shot will be administered four weeks later. It’s unclear what dosage schedule AstraZeneca will submit to regulators.

Will the vaccine be effective right away?

The Pfizer vaccine provides strong protection against COVID-19 within 10 days after the first dose, according to documents published by the FDA. Minnesota state epidemiologist Kris Ehresmann cautioned that it could take up to six weeks after the first dose for vaccines to provide full protection against COVID-19.

How long will the vaccines protect against infection?

We don’t know yet. It’s possible that these vaccines could provide long-lasting protection against the virus, or the protection could fade over time and require additional booster shots. The FDA said the Pfizer vaccine seems to provide protection for at least two months after the second and final dose.

Will I still need to wear a mask after vaccination?

Because it could take weeks for vaccines to provide full protection, state health officials stressed that it will be important that people continue to wear masks, maintain social distancing and quarantine after exposure to slow the spread of the virus.

Can children be vaccinated?

The initial rounds of vaccines will only be available to adults, according to state officials. Children may be eligible later.

Are the vaccines safe for pregnant or nursing women?

We don’t know yet. The first clinical trials did not study the safety of vaccines for women who are pregnant or breastfeeding. Vaccine manufacturers “have likely started expanding to pregnant people and some children as they get more data from the first part of their studies,” according to the Minnesota Department of Health. 

If I’ve already had COVID-19, should I get vaccinated?

Because re-infection is possible and may bring additional health risks, the U.S. Centers for Disease Control and Prevention (CDC) says vaccinations may be advisedfor those who have already been infected and recovered from COVID-19.

How much will it cost to get the vaccine?

Under Operation Warp Speed, the U.S. government contributed billions of dollars for the development of vaccines, and ordered hundreds of millions of doses. Federal health officials have pledged that vaccinations will be made available free of charge to all Americans. 

Will vaccinations be mandatory?

Health officials encourage people to get vaccinated and expect vaccinations to be available to everyone who wants one, but it will not be required by law. However, some employers may require their employees to be vaccinated.

The Associated Press contributed to this report.