The largest vaccination campaign in U.S. history is getting underway with health workers getting the first shots of the Pfizer-BioNTech vaccine.
On Friday, the FDA gave the green light on the world’s second rigorously studied COVID-19 vaccine, made by Moderna Inc. and the National Institutes of Health.
The hope is that vaccinations will eventually help beat back the pandemic - which has claimed nearly 300,000 lives in the United States.
Below are answers to some of the most common questions about the COVID-19 vaccine situation.
When will there be a COVID-19 vaccine?
The U.S. Food and Drug Administration gave emergency use authorization to Pfizer's two-dose vaccine and healthcare workers started getting the first shots on Monday, Dec. 14.
Moderna's two-dose vaccine received emergency use authorization on Dec. 18. Moderna has about 5.9 million doses ready for shipment set to begin over the weekend, according to Operation Warp Speed, the government’s vaccine development program.
Who gets the vaccine first?
The first doses are going to health care workers and long-term care residents, per the recommendation of the Advisory Committee on Immunization Practices. Current estimates project that no more than 20 million doses of each vaccine will be available by the end of 2020.
It's yet to be determined who will be next. Among the possibilities: teachers, police, firefighters and workers in other essential fields such as food production and transportation; the elderly; and people with underlying medical conditions.
Ultimately, it will be up to the states to decide who should receive the first vaccinations.
When will the general public get the vaccine?
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, and Health and Human Services Secretary Alex Azar have said average Americans are not likely to start getting the vaccine until March or April 2021.
Supply and worldwide demand will play a factor, but that supply will increase as more vaccines are approved. Canada and Britain had already approved the Pfizer vaccine before the U.S.
The Centers for Disease Control and Prevention says a COVID-19 vaccine may not be available for young children until more studies are completed.
Should pregnant women get the COVID-19 vaccine?
Pregnant women were excluded from participating in the Moderna and Pfizer studies, so it's still unknown how they could be impacted by the vaccines.
During Pfizer's study, 23 women did become pregnant during the study. Nine of them dropped out because of it. The rest are still being followed.
However, the American College of Obstetricians and Gynecologists said Sunday that vaccination should not be withheld from pregnant women who otherwise would qualify.
The bottom line is that it's up to you and your doctor to make that decision.
How many doses are needed?
The majority of the COVID-19 candidate vaccines require two doses. The number of days between the two doses varies based on the vaccine. The CDC says it’s between 21 and 28 days between doses, depending on the manufacturer.
The Johnson and Johnson/Janssen vaccine is the furthest along vaccine that requires only a single dose.
How effective are the vaccines?
Pfizer has reported its vaccine to be 94.5% effective in clinical trials. Moderna has said its vaccine is 95% effective.
The vaccine from AstraZeneca and Oxford University suggest the vaccine is about 70% safe. Still, experts say the AstraZeneca vaccine seems likely to be approved, despite some confusion in the results and lower levels of protection than what some other vaccine candidates have shown.
How long does protection last after taking the vaccine?
That's not clear, but it's something which could be answered by those taking part in Phase 3 of the clinical trials and the first people to get vaccinated, according to Johns Hopkins University. Fauci said he would be “surprised” if the vaccine gave lifelong immunity like the measles vaccine. Moncef Slaoui, head of the U.S. vaccine development effort, said he believes the vaccine’s effectiveness could last for “many, many years,” with older people and others who are more vulnerable requiring a booster every three to five years.
Will there be side effects?
Yes, says Dr. Matthew Woodruff, an immunologist at Emory University who studies the fundamentals of immune responses to vaccination.
He writes in The Conversation that vaccines work by training your immune system to recognize and remember a pathogen safely. Expected side effects include redness and swelling at the injection site and stiffness and soreness in the muscle.
A potent vaccine, he says, may even cause fever. Pfizer said during its trial 3.8% of vaccine recipients felt fatigued and 2% had a headache. Woodruff says this is normal.
"These are signs that the vaccine is doing what it was designed to do – train your immune system to respond against something it might otherwise ignore so that you’ll be protected later. It does not mean that the vaccine gave you COVID-19,” Woodruff says.
There were also some early questions from Britain after two people who received the vaccine suffered allergic reactions from the Pfizer vaccine. A similar occurrence happened to two health care workers in Alaska. Experts say such reactions are not unexpected and they are usually rare and short-lived.
If I’ve already had coronavirus, do I need the vaccine?
Fauci says it is necessary to get the vaccine because it isn’t certain how long natural immunity from the virus lasts. The CDC adds that early evidence suggests natural immunity, from those who’ve had the virus, may not last long. The agency also adds that immunity can vary from person to person.
When will there be “herd immunity” from COVID-19?
According to the World Health Organization, herd immunity is a term used to describe the point at which enough people are protected that the virus can be held in check. The percentage of the population required to develop herd immunity varies with each disease. Experts estimate at least 70% of the U.S. population needs to be vaccinated to achieve herd immunity.
Measles requires 95% of the population to be vaccinated, with the remaining 5% protected by those who are vaccinated and not spreading the virus.
Slaoui has estimated the country could reach herd immunity as early as May, based on the effectiveness of the Pfizer and Moderna vaccines.
Would you still be able to transmit coronavirus even after you’ve been immunized?
According to Dr. David Diemert, a vaccines expert from George Washington University, in the same way we don’t know if the vaccines stop the virus from coming into your body, we also don’t know about it leaving a vaccinated body.
“It doesn’t necessarily mean it wouldn’t stop someone from transmitting it to someone else,” he said.
Deborah Fuller, a vaccine expert at the University of Washington, says it's also not yet known whether the Pfizer and Moderna vaccines protect people from infection entirely, or just from symptoms. That means vaccinated people might still be able to get infected and pass the virus on, although it would likely be at a much lower rate.
RELATED: VERIFY: Will the COVID-19 vaccine stop you from spreading it to others? Experts don't know yet
Can I stop wearing a mask after I am vaccinated?
No. For a couple of reasons, masks and social distancing will still be recommended for some time after people are vaccinated.
To start, the first coronavirus vaccines require two shots; Pfizer’s second dose comes three weeks after the first, and Moderna’s comes after four weeks. And the effect of vaccinations generally isn’t immediate.
People are expected to get some level of protection within a couple of weeks after the first shot. But full protection may not happen until a couple of weeks after the second shot.
Can getting a vaccine make you sick with COVID-19?
"These leading vaccine trials don't have live virus in them," Dr. Linda Nabha, an infectious diseases specialist, said. "So you can't, for example, get COVID from these vaccines that don't have the live virus in them."
That fact was backed up by other experts.
"You cannot get COVID from the vaccine itself because the vaccine doesn't include the full COVID virus," Dr. David Diemert, an associate professor of medicine at the George Washington University said. "So it's not possible for the vaccine to suddenly make the virus in the person's body."
Can I still donate blood and plasma after getting vaccinated?
The latest update from the American Association of Blood Banks and FDA states that people who receive a vaccine can still donate blood but not plasma.
“You should not collect COVID-19 convalescent plasma from individuals who have received an investigational COVID-19 vaccine because of the uncertainty regarding the quality of the immune response produced by such investigational vaccines,” the document says.