Frequently Asked Questions

All approved COVID-19 vaccines (J&J, Moderna, Pfizer and Novavax) went through all the required stages of clinical testing needed to prove two things: that they’re safe and work to protect against COVID-19.

Real-world data supports this. Hundreds of millions of doses have been administered in the United States and billions have been administered around the world. Very few serious reactions have been reported.

Four conditions have occurred in vaccinated people. Some individuals developed anaphylaxis (a strong allergic reaction). Others developed myocarditis (inflammation of the heart muscle). Some people who received the J&J vaccine have reported a certain type of blood clot called thrombosis with thrombocytopenia syndrome (TTS) or Guillain Barré Syndrome, a condition in which the immune system attacks the nerves.

You can keep up with the latest data on these events on the CDC’s website. But keep in mind that of the millions of people who were vaccinated, only a small percentage have developed any of these conditions. Out of every one million vaccinated people, about five people went into anaphylaxis. The CDC continues to monitor cases of myocarditis, and most people responded well to treatment and felt better quickly, per the CDC. For each one million doses of the J&J vaccines administered, four developed TTS. Rare cases of Guillain Barré Syndrome have also been reported following the J&J vaccine largely among men over 50 years of age.

The risk of experiencing these complications is extremely low. Meanwhile, there are serious risks associated with COVID-19, including severe illness or hospitalization.

The CDC takes safety very seriously and continues to monitor these vaccines calling the effort “the most intense safety monitoring” in U.S. history.

Yes! One especially notable study was released in September 2021 by the CDC. The study followed 3,689 people between March and August 2021. The results showed that the Moderna vaccine was 93% effective against hospitalization, the Pfizer vaccine was 88% effective against hospitalization and the J&J vaccine was 71% effective against hospitalization. This study evaluated the efficacy against the original coronavirus variant.

The Novavax COVID-19 Vaccine, Adjuvanted, was evaluated in a randomized, blinded, placebo-controlled study conducted in the United States and Mexico. The study evaluated the efficacy of the Novavax vaccine against the original coronavirus variant. It found that Novavax was 90.4% effective in preventing mild, moderate or severe COVID-19 among people 18 years and older. The vaccine was 78.6% effective in the subgroup of individuals 65 years of age and older.

Vaccines are still protective against severe COVID-19 caused by the Omicron variant and its subvariants, now dominant in the United States, but a booster shot is needed to ensure protection. One study released in March 2022 followed patients from 21 U.S. medical centers between March 2021 and January 2022. During the Omicron surge, the study found that people who received three mRNA shots (a course of Pfizer or Moderna, plus a booster) were 94% less likely to die from COVID-19.

The original coronavirus vaccines still protect against severe illness and death, but the CDC has now authorized booster shots for everyone over the age of five. Given the contagious nature of Omicron and its subvariants, now dominant in the U.S., boosters are essential to provide sufficient protection.

A CDC study released in January 2022 shows just how important this is. One study looked at the rate of severe and hospital-grade COVID cases in eight states, across over 300,000 people. Getting a third mRNA vaccine was 90% effective in preventing hospitalizations from COVID-19 caused by Omicron. Data from 21 U.S. medical centers collected between March 2021 and January 2022 found that people who had received three mRNA shots were 94% less likely to die when infected with Omicron.

CDC research has shown that booster shots are safe. It’s normal to feel fatigue or head and muscle aches after a booster, but these symptoms are less common after a booster than after a second mRNA shot, a February 2022 CDC study suggests.

As of late May, the CDC recommends immunocompromised individuals 12 years of age and older and everyone 50 and older to receive the second booster shots at least 4 months after their first booster. Adults of any age who received a J&J primary vaccine and booster may receive a booster shot. In that case, the CDC recommends opting for an mRNA booster shot.

If you are older than 18 and received the second Pfizer or Moderna shot 5 or more months ago you can now receive a booster shot according to the latest CDC guidance. You can receive a booster shot made by J&J, Moderna, or Pfizer regardless of which shot you had already received.

Children over age 5 may also receive a booster made by Pfizer.

If you are 18 and older and received the J&J shot 2 or more months ago, you are eligible to receive a booster shot made by J&J, Moderna, or Pfizer. The CDC recommends that people who received a J&J original shot opt for mRNA booster shots in the future, based on research suggesting that mRNA shots provide more robust protection.

No, a booster shot is not yet recommended at this time.

If you are 18 and older and received the first Novavax shot, you should get your second dose 3 to 8 weeks after receiving the first. You are fully vaccinated and up to date 2 weeks after your second dose in the primary series. The Novavax vaccine is not authorized for use as a booster dose at this time.

Adults 18 and older may receive a booster shot made by Pfizer, Moderna, or J&J. The Novavax vaccine is not authorized for use as a booster dose at this time. Children over age 5 are only eligible for booster shots made by Pfizer. Boosters are not yet available for children 6 months to 5 years of age.

For example, if you first received a Moderna vaccine and are eligible for a booster, you can receive a booster shot made by Pfizer or J&J. You would receive that booster at least 5 months after getting your second dose. That said, the CDC recommends that you opt for an mRNA vaccine as a booster shot, as opposed to the J&J.

Here’s another example. If you received a J&J vaccine and are eligible for a booster, you can receive one made by either Pfizer or Moderna. You would receive your booster 2 months after your first shot.

The CDC has been studying the safety of booster shots. A February 2022 study evaluating 721,562 adult booster shot recipients found that the most common side effects were fever and pain–both common reactions to vaccination. Those who got booster shots different from their original shots were more likely to report side effects compared to people who stuck with the same brand. But the CDC still notes that mixing and matching boosters is safe.

Several studies speak to the safety of booster shots. The first followed over 700,000 people 18 and older who had received a booster shot between September 2021 and February 2022 and reported their side effects to the CDC. Ninety-two percent of those reports were not deemed serious. Medical care was rarely sought after receiving a booster shot.

The most common side effects were headache, fever, and pain. These symptoms were slightly more common among people who received a different booster shot from the shot they already received. But side effects are more likely to occur after the second dose of a vaccine compared to after administration of the booster.

That said, the CDC recommends that you opt for an mRNA vaccine as a booster shot, as opposed to the J&J.

If you have confirmed with a PCR test that you have contracted COVID-19, you should wait until your symptoms resolve and you’ve ended your isolation period to get a booster shot. You may consider delaying your next vaccine dose by 3 months from symptom onset or a first positive test, as reinfection is less likely in the first weeks or months following a COVID-19 infection. You should consider your personal risk of developing severe disease and the infection rates in your community when making the decision.

After that, though, it is critical to restore protection with a booster shot as vaccines offer added defenses to your immune system. The CDC reports that people who had a COVID-19 infection and did not get vaccinated after recovery are more likely to get reinfected than those who were vaccinated.

The CDC also recommends that adults and children who have multisystem inflammatory syndrome (MIS) should wait to get vaccinated until they recover from being sick or after 90 days after their diagnosis with MIS-A or MIS-C.

The Omicron variant and its various subtypes are the dominant forms of SARS-CoV-2 in the U.S. as of August 2022.

Protection Against Omicron

There is evidence that existing two-dose vaccine regimens are less effective against Omicron than they were against Delta and the original coronavirus. However, booster shots can help restore protection. A January 2022 study of over 300,000 people showed that an mRNA booster shot was 90% effective against hospitalization with Omicron.

More recent research contains more good news. A March 2022 study from 21 U.S. medical centers found that a three-dose mRNA vaccine regimen could reduce both the chances of ventilation (an extreme form of care) and of death from Omicron by 94%.

While protection is still high, it can wane over time. A CDC study published in February 2022 showed that 2 months after the first shot vaccines were 90% protective against hospitalization. Four months after the third shot, that protection dropped to 78%. (This data was collected during the Omicron wave in early 2022.) The best course of action, per the CDC, is to get vaccinated and get your booster if you are eligible.

Protection Against BA.5 (Omicron subvariant)

The Omicron subvariant BA.5 is the dominant form of the SARS-CoV-2 virus in the United States and is potentially the most contagious strain of the virus to date. (The latest breakdown of variant proportions is available on the CDC website).

Symptoms for BA.5 are similar to the earlier version of Omicron including cough, runny nose, sore throat, fatigue, headaches or muscle pains. Patients are more likely to present with upper respiratory infections and less likely to lose their senses of taste and smell or experience shortness of breath.

Vaccines provide durable protection against severe illness including hospitalizations and deaths and limited protection against symptomatic disease caused by Omicron and its variants. Boosters help restore protection against symptomatic disease, although it wanes within months of receiving them.

The short answer is yes.

While you may have COVID-19 antibodies (proteins that bind to the virus and tell the body to vanquish it) in your body after you recover, we don’t know how long immunity gained from natural infection lasts.

If you had COVID-19 recently, you may consider delaying your next vaccine dose by 3 months from symptom onset or a first positive test, as reinfection is less likely in the first weeks or months. You should consider your personal risk of developing severe disease and the infection rates in your community when making the decision.

Some studies suggest as many as one-third of mild COVID-19 cases don’t leave behind protective antibodies. One CDC study from September 2021 followed 72 people, most of whom had mild cases. About 36% of them did not develop antibodies.

It’s possible more severe cases of COVID-19 may leave behind more antibodies, but these cases are very risky. Even if the case doesn’t lead to hospitalization or death, there could be long-term consequences from the condition.

The most reliable way to train your immune system to fight COVID-19 is to get vaccinated, rather than risking a so-called “natural infection.” You don’t need to risk short-term or long-term consequences of the virus to protect yourself.

Getting sick with one variant also doesn’t guarantee protection from another. Some early research suggests that Omicron is more likely to cause re-infection than Delta is.

There’s one more reason to get vaccinated: You can help protect others by reducing your chances of being hospitalized. The Omicron variant and its subtypes are more contagious than the original coronavirus. This means it is even more critical to get vaccinated and boosted to keep hospitals from becoming overwhelmed.

Real-world research has shown that immunity is improved after two shots. For instance, the effectiveness of one Pfizer or Moderna vaccine against the original coronavirus was 64% in a study of U.S. health care workers done by the CDC. But two shots raised the efficacy to around 94% in that study.

In light of new variants such as Omicron, it’s even more important to get both doses of your COVID-19 shot and stay up to date on the boosters.

You should talk to your doctor if you are pregnant and are worried about getting a COVID-19 vaccine. However, the CDC now strongly recommends pregnant people (or those who want to become pregnant) get the COVID-19 vaccine.

One study published in the New England Journal of Medicine followed over 35,000 pregnant women who got vaccinated. The study found no signs that the vaccine was linked to any complications. Studies from Norway, Israel and the U.S. showed that mRNA vaccines were also not linked to an increased risk of miscarriage, preterm birth or other adverse outcomes.

Getting vaccinated while pregnant can even help protect newborn children from COVID-19. A CDC study released in February 2022 analyzed data from 20 pediatric hospitals in the U.S. Vaccination among pregnant mothers was linked with a 60% reduction in the risk of infants (younger than 6 months old) being hospitalized with COVID-19.

Meanwhile, evidence also shows that pregnant women who get COVID-19 are at higher risk of getting very sick from the virus itself compared to non-pregnant women of the same age. This means protecting against the virus with a vaccine is even more important.

You may have heard some misinformation suggesting that the vaccines might impair a woman’s ability to get pregnant. Scientists have debunked this claim.

In a joint statement, the American Society for Reproductive Medicine, the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine said there is no evidence the vaccine impacts women’s fertility. The idea that there could be fertility loss due to vaccination was “scientifically unlikely,” the statement read.

Another major study released in 2022 confirms that the COVID vaccines are not linked to fertility issues. The study followed over 2,000 females who provided information on their efforts to conceive and the vaccination status of their partners. Fertility rates among women who had received at least one vaccine didn’t differ from unvaccinated women. The pattern held for men as well. The Mayo Clinic also notes that there is “no evidence” that COVID-19 vaccines can cause fertility problems.

On June 19, the CDC recommended that everyone over 6 months old gets vaccinated against COVID-19. Children get a smaller dose of the vaccine compared to adults and the coronavirus vaccine may be given to children at the same time as other vaccinations.

Children between 6 months and 5 years of age may receive the primary vaccine series made by either Pfizer or Moderna. For children between 6 months and 4 years old, the Pfizer primary series has three doses of the vaccine and the Moderna primary series has two doses. Five-year-old children are eligible to receive a two-dose primary vaccine series produced by either Pfizer or Moderna.

Children aged 6 and older are eligible for Pfizer’s two-dose coronavirus vaccine. If your child is 12 or older, they will receive the same version of the vaccine given to adults. If they are between 5 and 11, they receive a slightly lower dosage.

As of May 2022  children aged 5 and over are eligible for booster shots made by Pfizer. They may receive boosters 5 months after they complete their primary vaccine series.

The CDC currently recommends that children aged 6 months or older get a coronavirus vaccine. These recommendations were made after studies specifically evaluated the safety of the coronavirus vaccines in children and the data was reviewed by outside experts.

For example, a clinical trial on 2,260 adolescents aged 12 to 15 found no serious adverse effects linked to the Pfizer vaccine. By December 2021, about 8.7 million children aged 5 through 11 had received a vaccine with very few serious side effects reported. Most reactions were mild and included pain in the injection site, fatigue and headache.

The most common side effects reported for children 6 months to 3 years old are pain at the injection site, swollen lymph nodes, irritability or crying, sleepiness and loss of appetite. For kids 4 to 17 years of age, side effects are more common after the second dose and include pain and swelling at the injection site, fatigue, headache, muscle pain, chills and swollen lymph nodes.

Data from the CDC’s vaccine safety monitoring between December 2020 and August 2021 has shown a small but increased risk of myocarditis—inflammation of the heart muscle—in male adolescents and young adults after receiving Pfizer or Moderna vaccines. Rates of myocarditis were highest following the second dose of an mRNA vaccine among males 12 to 24. As of August 11, 2022, 1020 cases have been reported in over 58 million doses of vaccine administered in children and teens under 18, and 667 have been verified as myocarditis.

Side effects for booster shots were mild as well, per a March CDC study. The most common side effects were injection site pain, fatigue, headache and muscle pain, which usually manifested the day after getting a booster.

Children 6 months and older are eligible to receive coronavirus vaccines. The FDA evaluated data provided by Pfizer and Moderna for vaccine safety and efficacy. Data from 5,400 children under 5 years old showed that Moderna’s regimen was 50.6% effective in preventing COVID-19 in children 6 to 23 months and 36.8% effective for kids between ages 2 and 5.

A small vaccine efficacy study of 220 kids by Pfizer evaluated by the FDA found that in children aged between 6 months and 4 years old that the immune response in kids was similar to participants aged 16 to 25. For kids 5 through 11, the CDC estimates that the Pfizer vaccine is 90% effective against COVID-19. That figure was also echoed in Pfizer’s study of the vaccine.

Real-world data has shown that vaccines have already been protecting adolescents, who became eligible to receive their shots earlier than children younger than 12. A study published in the New England Journal of Medicine in January 2022 found that the Pfizer vaccine was 94% effective in preventing hospitalizations among adolescents aged 12 to 18.

A CDC study released in March on the effectiveness of the vaccines in protecting against infections found that two doses of the Pfizer vaccine reduced the risk of infection from Omicron by 31% in children 5 to 11 years old and 59% in teens 12 to 15 years of age. Another CDC study released in March found that the vaccine was 51% effective against emergency visits in children 5 to 11 years old, between 2 weeks and 2 months post-second shot. Over that time, it was 45% effective in adolescents aged 12 to 15, and 34% effective in teens aged 16 and 17.

However, a booster shot, which is now available for children over 5 years old, restored protection to 81% in teens 16 and older.