Vaccines are here, and there's no shortage of questions amid the rollout. New questions arise daily, but this is what we're hearing now, and the answers based on what we know today.
Do you need to get the vaccine if you've already had COVID-19?
There isn't enough information about how long a person remains protected through natural immunity from prior infection. The CDC found early evidence that suggested natural immunity might not last long.
However, the CDC has no comment on whether people with prior COVID-19 infections should get the vaccine until the Advisory Committee on Immunization Practices makes recommendations. The CDC hasn't stated if the committee will make any such recommendation.
If you get the vaccine, do you still need to wear a mask?
Yes. Banner Health's Dr. Josh Lee told Pima County says the vaccine is just one part of a broad toolkit in mitigating the effects of COVID-19.
He said that while the vaccines reduce the disease, it'll take more time to figure out if it reduces transmission. Lee said mitigation efforts like masks and physical distancing remain important for those who do get the shot because it would take time to vaccinate the bulk of the population.
Who is paying for the vaccines, and do you have to be an Arizona resident to get it here?
The vaccine doses are free thanks to the taxpayers. But vaccine providers can charge a fee for giving the shot to someone. Best answer is to ask your vaccine provider before if there is a fee.
Providers can get reimbursement from a recipient's insurance or through the Health Resources and Services Administration's Provider Relief Fund.
Pima County plans to make the vaccine available to anybody regardless of residency or citizenship.
The vaccine requires two doses. What if you can't get the second dose on schedule?
Vaccine providers will give a vaccination card with the first dose. The card will indicate when to receive the second shot. You need both doses to be considered fully vaccinated.
Moderna and Pfizer say their vaccines are 95 percent effective based on a two-shot regimen. If you don't get the second shot or get it late, the vaccine's effectiveness would not be 95 percent against a COVID-19 infection.
Crystal Rambaud, the county's Manager for Vaccine Preventable Diseases, said there's no need to start the two-shot regimen over if someone misses their second dose in the recommended time frame, and people should still get it, even if it's late.
Are Pfizer and Moderna's vaccines interchangeable or should your second dose be the same brand as the first?
Pfizer-BioNTech's fact sheet for providers said people who receive the manufacturer's vaccine should have a second dose from the same company. Pfizer said there are no data about whether the company's vaccine is interchangeable with any other COVID-19 vaccine.
Are there vaccine side effects?
Pfizer reported several possible side effects:
•Injection site pain, swelling or redness.
•Swollen lymph nodes
The company said trials show the vaccine prevents COVID-19 after two doses, three weeks apart. But how long the protection lasts remains unknown.
Pfizer's authorization allows the vaccine for those 16 years and older.
Moderna reported several possible side effects:
•Injection site pain
•Swollen lymph nodes
The public would receive Moderna's larger two-dose regimen four weeks apart. Moderna tested its vaccine on those 18 and older.
Neither vaccine would infect someone with COVID-19.
Should you feel anything after receiving the vaccine?
Yes. The CDC said some side effects like pain or swelling in the shot arm are normal, as are fever, chills, headache and tiredness throughout the rest of the body.
That's a good thing. Those side effects are signs that your body is building protection against COVID-19. The CDC said the side effects should go away in a few days, but they could affect daily activities until then.
The CDC warned that recipients might experience flu-like effects after the first shot, but people should still get the second when required unless a healthcare provider advises otherwise.
The two-shot vaccines might not protect recipients until one to two weeks after the second shot.
Side effects should concern recipients if redness or tenderness at the shot site increases after 24 hours or they don't go away after a few days.
What is herd immunity and why are we talking about it?
The World Health Organization defines herd immunity as a concept where an achieved vaccination threshold would protect an entire population from a given virus. The WHO doesn't include infection as a means to herd immunity.
The vaccinated percentage to achieve herd immunity varies by the virus. Measles requires 95 percent vaccination, polio is 80 percent.
Vaccinating a population to receive herd immunity would lower a virus' ability to spread.
The CDC takes a different view of herd immunity — it's when enough people are protected from a virus or bacteria through vaccination or previous infection. The CDC doesn't have an estimate of the vaccinated population percentage needed to achieve herd immunity for COVID-19.
The nation's senior infectious disease official Dr. Anthony Fauci said the U.S. could start seeing an impact after 50 percent of the population receives the vaccine. However, he said 75-85 percent would need vaccinations for herd immunity.
Are there different COVID strains?
Yes. There are seven human coronaviruses, including novel coronavirus (SARS-CoV-2), or COVID-19. Human coronaviruses were first discovered in the mid-1960s.
Four strains are common, but SARS, MERS and COVID-19 are not among them.
Manufacturers have been working on vaccines for COVID-19, which is the cause of the pandemic. There's been no discussion on their effectiveness for other coronaviruses.
Are Pfizer and Moderna's vaccines the only two that will be available in the United States?
Pfizer's vaccine already received Emergency Use Authorization from the FDA and administered throughout the country, including Arizona.
Moderna received approval Friday.
The CDC said there were five vaccines in progress or planned for phase 3 trials in the United States as of Nov. 24.
The WHO reported there were more than 50 vaccines in trials worldwide.
On Thursday, Johnson & Johnson announced it enrolled about 45,000 people in a multi-country Phase 3 trial for a single-dose COVID-19 vaccine.
Does the speed of the vaccine's approval make it less safe than other vaccines?
The Food and Drug Administration can issue an Emergency Use Authorization during public health emergencies to make medical countermeasures available. The speed at which COVID-19 vaccines are making their way to the public is due to the FDA issuing EUAs.
EUA vaccines for COVID-19 go through three phases before the FDA authorized their use.
In phase 1, a small group of healthy people received the vaccine to gauge its safety with increasing doses and learn how well it induced an immune response.
Phase 2 expanded the group to hundreds of people with varying health statuses and demographic groups using randomized-controlled studies. The second phase also varied the doses.
Phase 3 tested the vaccine on thousands of people and provided more information about the immune response in people who received the vaccine compared to those given a placebo.
The FDA expects the vaccine's manufacturer to continue clinical trials and pursue license approval. The FDA and CDC also conduct post-authorization monitoring for safety.
Pfizer's clinical trials included about 20,000 people, 16 years and older, who received at least one dose.
Moderna administered 15,000 placebos and 15,000 vaccines to people 18 years and older.
Why are there different storage temperature requirements between Pfizer and Moderna's vaccines?
Moderna's vaccine requires cold storage temperatures of minus-13 to 5 degrees Fahrenheit. Pfizer's vaccine requires a much more frigid minus-112 to minus-76 degrees.
In an interview with National Public Radio, vaccine researcher Margaret Liu said the vaccines need such temperatures because of the makers' approach using mRNA, or messenger RNA, which gets the body to produce a protein that fights COVID-19.
Because mRNA is destroyed easily, vaccine makers stabilize the mRNA and add a coating for added protection. But that's still not enough. And in comes the cold temperatures.
The chemical reactions that break down the mRNA slow down as the temperature drops.
Moderna spokesperson Colleen Hussey said they uses a different structure and lipid nanoparticle properties to stabilize and coat their vaccine. The result is Moderna's vaccine doesn't require temperatures as low as Pfizer's.