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COVID-19 vaccine FAQ: Answers to your most common questions

Dr. Jha on COVID vaccines for kids under 5
Dr. Jha on CDC recommendations of COVID vaccines for kids under 5 03:48

More than years into the coronavirus pandemic, life-saving vaccines are helping to turn the tide against the deadly illness.

But as the vaccines have rolled out, so have the questions: Who should get it? What's safe to do once you're vaccinated? What about breakthrough cases? 

Here are the answers to your most frequently asked questions about the vaccine, including its effectiveness, its risks, and what to expect when it comes to side effects.

How can I get the COVID vaccine?

Vaccines are now widely available across the U.S. and eligibility has expanded to include all adults and children ages 6 months and older.

More than 221 million people in the U.S. have been fully vaccinated as of mid June, the CDC reports.

Doses are available — at no cost — at thousands of vaccination sites and pharmacies across the country. 

To find a location near you, visit the website, text your ZIP code to 438829, or call 1-800-232-0233 (the CDC says the call center operates in 150+ languages).

Can children get the vaccine?

The CDC recommends children get vaccinated against the virus. Though children are generally at lower risk of severe COVID-19 compared to adults, thousands of kids have been hospitalized and hundreds have died of it — including some with no prior health conditions.

The Pfizer vaccine received authorization for adolescents age 12 to 15 in May 2021, after clinical trial results showed it is safe and effective in that age group. 

Lower-dose shots of the Pfizer vaccine for children ages 5 to 11 became available in November 2021 after the FDA authorized it and the CDC director recommended it for kids 5 and up.

Then in June 2022, Pfizer and Moderna vaccines were OK'd for kids starting as young as 6 months old.

CDC recommends COVID vaccines for children 5 years old and younger 04:24

Johnson & Johnson's vaccine is authorized only for ages 18 and up.

What are the differences between the COVID vaccines?

In December 2020, the FDA authorized emergency use of the first two coronavirus vaccines in the U.S., one made by Pfizer and BioNTech, and the other by Moderna. Both require two doses. A third vaccine, from Johnson & Johnson's Janssen Biotech division, got FDA authorization in late February 2021 and only requires one shot.

All three proved highly effective at preventing severe illness, hospitalizations and deaths from COVID-19. 

Pfizer's vaccine became the first to be granted full FDA approval, followed by Moderna's. The Pfizer and Moderna vaccines are both made using messenger RNA, or mRNA, technology.

Traditionally, vaccines have been made from a weakened or inactivated germ that trains the immune system to fight off infection if it encounters the virus in the future. But mRNA vaccines do something different: They teach human body cells how to make a harmless piece of a protein — a "spike protein" — that's also found on the surface of the coronavirus. After that protein piece emerges on the surface of a cell, the human immune system recognizes it and begins making antibodies for it — which offer protection if the person is exposed to the actual virus in the future.

One difference between the Pfizer and Moderna vaccines is the wait time between the two required doses: Pfizer's are given 21 days apart, while the Moderna shots are given 28 days apart. 

Johnson & Johnson took a different approach, developing what's called a viral vector vaccine — a type that has been used for years against other diseases. It uses an altered, harmless, non-replicating version of a common cold virus, called adenovirus type 26, to introduce genetic instructions for the "spike protein." The immune system responds by making antibodies which will protect the person if they're infected by SARS-CoV-2, the virus that causes COVID-19, in the future.

Johnson & Johnson's single-dose vaccine has the advantage of being stored in regular refrigerators, while the two others must be stored and transported at below-freezing temperatures. 

What are the side effects of the COVID vaccines? 

In general, side effects are not uncommon with vaccines, and the COVID-19 shot is no exception. Your body's immune reaction could include the same kinds of side effects often seen with other vaccines, including a sore arm, fatigue, fever, chills or headaches.

"This is expected," Dr. Neeta Ogden, an internal medicine specialist and immunologist, said in an interview on CBSN.

"People should maybe think about vaccinating on weekends, for example," she said. "You probably might need to take a day off from work. … This is predictable and I don't think that it is alarming."

Not everyone experiences side effects, but doctors stress that their occurrence is normal and should not discourage people from getting the shots. 

More severe side effects are extremely rare. There have been a small number of cases of a type of heart inflammation called myocarditis, mostly in younger men, after receiving the Moderna or Pfizer vaccine. (Health experts note there's a greater risk of developing myocarditis after a COVID-19 infection than after getting vaccinated.)

The Johnson & Johnson vaccine has been linked to rare cases of blood clots, including nine deaths, out of 16 million people who received the shot in the U.S. That risk led the CDC to recommend in December 2021 that people opt for the Pfizer or Moderna vaccines instead when possible. 

Can the side effects be minimized?

The CDC offers some advice on ways to combat vaccine side effects: After vaccination, use or lightly exercise the arm that got the shot. Take Tylenol or Motrin for any pain you may have, but only after you've gotten the shot, not before. The CDC also recommends drinking plenty of liquids after you get either the first or second dose. If redness or tenderness increases at the vaccination site in the days following the shot, the CDC recommends that you call your doctor.

Do the COVID vaccines protect against new variants? 

Health officials say the vaccines still offer protection against severe illness from the current variants.

Recent data from the Centers for Disease Control and Prevention show that adults who are unvaccinated are four times more likely to test positive for COVID and 15 times more likely to die of it than those who are fully vaccinated. Compared to those who received a booster dose, the unvaccinated are 13 times more likely to test positive and 68 times more likely to die.

But the Omicron variant, first identified around Thanksgiving 2021, appears to be able to cause more infections even in people who were vaccinated or had a previous case of COVID-19. Experts say getting a booster shot helps restore protection against severe illness and hospitalization.

Omicron is one of five current "variants of concern," identified by the Greek letters Alpha, Beta, Gamma, Delta and Omicron. Delta, which turned up in the U.S. in the spring of 2021, is more contagious than previous strains and quickly made up the overwhelming majority of U.S. cases — about 99%. 

Data from scientists in South Africa, where Omicron was first identified, and in the U.K. show Omicron spreads even more rapidly.

Experts have also kept an eye on the Mu variant, which emerged in Colombia in January 2021 and has mutations suggesting it may be able to bypass existing coronavirus antibodies. 

"But there isn't a lot of clinical data to suggest that. It is mostly laboratory in vitro data," Dr. Fauci said. "...We don't consider it an immediate threat right now." 

Who shouldn't get a COVID vaccine?

The CDC says people allergic to the ingredient polyethylene glycol (PEG) or polysorbate, which is similar, should not get an mRNA COVID vaccine, and anyone who has an immediate allergic reaction to the first dose should not get the second one.

A handful of people suffered adverse reactions, including anaphylaxis, after getting the vaccine, but all recovered.

People with a history of allergic reaction to a vaccine or injectable therapy for another disease should talk to their doctors, the CDC advises. It says people with food allergies do not need to avoid the vaccine.

Should you get a COVID vaccine during pregnancy?

The CDC updated its guidance to "strongly recommend" that people who are pregnant or planning to become pregnant should get vaccinated against COVID-19, citing a growing amount of data verifying the safety of the vaccines during pregnancy.

"I would say if you're pregnant, not only is it a good idea to get the vaccine on the basis of safety, but it's highly effective and important because you are at increased risk of bad outcomes if you get COVID," said Surgeon General Vivek Murthy. 

CDC recommends pregnant women get COVID-19 vaccine 07:46

Although pregnant people were not included in the initial clinical trials, tens of thousands of pregnant women have now gotten the shots safely. Additional research has found no safety issues, no increased risk of miscarriage and no impact on fertility.

Many doctors say the shots are especially important because of the higher risk of severe illness in women who contract COVID-19 during pregnancy. The virus also raises risks to the unborn baby, including stillbirth.

"I recommend highly that all pregnant women be immunized, from initial discovery of the pregnancy right up to term," Dr. Bob Lahita, professor of medicine New York Medical College and chairman of medicine St. Joseph University Hospital, said on CBSN. He said there is "no evidence" that the vaccine "has any effect on the placenta, on the fetus, on the mother. Except if one gets the infection, the COVID, and you are pregnant, you run the risk of becoming very, very sick."

How long will COVID vaccine protection last? 

Researchers and health experts say they don't yet know for sure. On its official web FAQ, the CDC says, "We won't know how long immunity lasts after vaccination until we have more data on how well COVID-19 vaccines work in real-world conditions."

Moderna CEO Stephane Bancel offered a rough window: "We believe there will be protection potentially for a couple of years."

But amid the spread of the more transmissible Delta variant and evidence that vaccine efficacy is waning somewhat, U.S. health officials began rolling out booster shots to increase protection.

What's a booster shot and when can I get one?

A "booster" refers to an extra dose for those whose immune systems responded well to the initial vaccines but might face waning efficacy as time goes on.

Pharmacies began offering third doses to fully vaccinated immunocompromised patients in August 2021. Over the following weeks, the FDA and CDC cleared the way for a much broader swath of Americans to receive boosters.

The latest CDC guidance recommends boosters for people ages 12 and up. People who got the Pfizer or Moderna vaccines are eligible for a booster five months after getting their second dose. People age 50 and up are also recommended to get a second booster four months later.

Boosters are also recommended for all recipients of the Johnson & Johnson vaccine who were vaccinated two or more months earlier. The FDA is also allowing adults to mix-and-match their booster shots with different brands from their original vaccine.

Those who are moderately or severely immunocompromised, such as those with an organ transplant or cancer patients, can also get a fourth dose

Research from the CDC indicates side effects from booster shots are generally "mild to moderate" and similar to the first two doses. 

Can you still spread COVID after getting the vaccine?

People who receive a vaccine dramatically lower their chance of getting sick from the virus, though in a relatively small number of cases, people may catch what's known as a breakthrough infection despite being vaccinated. Vaccinated people who contract the virus may have a high viral load for a period of time, even if they don't develop symptoms. But most research indicates the vaccines help reduce its spread.

What are my risks of a breakthrough infection?

With the spread of the Delta and Omicron variants, instances of breakthrough infections — catching COVID even after being vaccinated — became more common. However, vaccination, especially with a booster shot, remains extremely effective at protecting people from severe illness, hospitalization or death.

Do I still need to wear a mask after receiving a COVID vaccine? 

Once you've gotten vaccinated it takes about two weeks for the body to develop immunity, so you'll need to continue taking precautions like social distancing and wearing masks to reduce your risk of infection during that time.

After that, the CDC says it is safe for fully vaccinated people shed their masks in some situations, although it urged the continued use of masks indoors in areas of higher transmission. Masks are still required for everyone in certain venues like health care facilities.

Many states have since dropped their mask mandates.

What can I safely do after I am fully vaccinated?

Once people are fully vaccinated — meaning two weeks have passed after their final dose — the CDC is assuring Americans that they can can resume most activities and gather with other vaccinated people, indoors or outdoors.

Vaccinated people no longer need to self-quarantine after travel. The CDC has a more detailed list of do's and don'ts here

Can employers force you to get vaccinated?

Many large companies already do, and President Biden is following suit.

On September 9, 2021, Mr. Biden announced new COVID-19 vaccine requirements, which will affect roughly 100 million Americans. The new measures include a vaccine mandate for all federal workers and contractors, and a requirement that companies with over 100 employees mandate vaccines or regular testing. 

The Department of Labor's Occupational Safety and Health Administration (OSHA) is developing a rule requiring those employers to make sure their workforce is fully vaccinated or require unvaccinated workers to get a negative test at least once a week.

Biden targets workers with new COVID vaccine mandate 03:50

"Generally speaking, employers are free to require safety measures like vaccination with exceptions for certain employees," said Aaron Goldstein, a labor and employment partner at the international law firm Dorsey & Whitney. "So the answer is likely to be yes, with an asterisk." Many hospitals, for example,  have long required staff to get vaccines, with exemptions allowed for medical or religious reasons.

American workers largely back employers making that call. More than half of those in one recent poll say they favor requiring vaccination for their workplaces.

Do I need to get vaccinated if I've already had COVID?

Even after you've gotten sick from COVID-19 and recovered, you could still get it again. So-called natural immunity varies from person to person. The vaccines, on the other hand, provide a reliably high level of protection.

That said: If you were treated with monoclonal antibodies or convalescent plasma during your illness, you should wait 90 days before getting a COVID-19 vaccine. The CDC also recommends you should talk to your doctor before proceeding.

What are the ingredients in COVID vaccines?

The FDA has posted detailed information on its website, including a full list of ingredients for the Moderna, Pfizer and Johnson & Johnson vaccines.

Why are the Pfizer and Moderna vaccines two doses?

For these vaccines to reach maximum effectiveness, two doses are needed. The first injection starts building protection in the immune system. A second shot increases the amount of that protection to more than 90% against the virus.

In reporting on this issue, CBS MoneyWatch senior reporter Stephen Gandel uncovered concerns that getting only one of the two shots might actually make the pandemic worse over time.

"The concern is that if people get one shot, and not two shots, and those people get exposed to the coronavirus, the virus won't get killed off [from] them… and the virus will figure out a way to adapt itself, and then it could spread again. Then we could have a vaccine-resistant strain of the coronavirus out there," he explained.

Why was there a temporary "pause" on the Johnson & Johnson vaccine?  

On April 13, U.S. health officials recommended a temporary "pause" in use of the Johnson & Johnson vaccine after several instances of rare blood clots were reported. Health officials identified 16 cases, mostly among women under the age of 50, three of whom died, out of more than 6.8 million people who had received doses of the Johnson & Johnson vaccine. 

The pause was lifted 10 days later after a CDC panel of medical experts determined that the benefits of the vaccine outweigh the risks. A warning was added about an increased risk of rare but serious blood clots for women under 50.

The CDC and FDA said the blood clots, called cerebral venous sinus thrombosis, were seen alongside low levels of blood platelets — an unusual combination that requires specialized treatment. The agencies said the "adverse events" seem to be extremely rare, but that the pause was important so that health care providers could be made aware of how to recognize and manage such cases.

"One of the things you can take away from all of this is that when the surveillance system, the CDC and the FDA, say that something is safe, you can be sure that it's safe," Dr. Anthony Fauci, the nation's top infectious diseases expert, said.

As additional data emerged about the risk, the CDC began recommending a preference for people to receive the Pfizer or Moderna vaccine instead of Johnson & Johnson's, though all three options remain available.

How many people need to be vaccinated before we reach herd immunity?

Experts haven't reached a consensus on exactly what it will take for the world to achieve herd immunity — a level of widespread protection that leaves the virus few remaining targets, so outbreaks can no longer flourish. 

A large majority of the population will need to be vaccinated before it can happen.

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