Understanding COVID-19 Vaccines
As of October 2021, one COVID-19 vaccine has been approved by the U.S. Food and Drug Administration (FDA), and two have been authorized for emergency use.
Pfizer, Inc., and BioNTech BNT162b2: On August 23, 2021, the FDA approved the Pfizer-BioNTech vaccine — called Comirnaty — for people age 16 and older. The vaccine is still available under emergency use authorization for children and teens 5 to 15 years old. View the infographic to see what is in the Pfizer COVID-19 vaccine.
ModernaTX, Inc., mRNA-1273: On December 18, 2020, the FDA authorized emergency use of this NIH-funded COVID-19 vaccine in the United States for people age 18 and older. View the infographic to see what is in the Moderna COVID-19 vaccine.
Janssen Pharmaceutical Companies of Johnson & Johnson: On February 27, 2021, the FDA authorized emergency use of this single-shot vaccine for people age 18 and older. Developed with support from NIH, this vaccine does not require special refrigeration. Women younger than 50 years old should be aware of the rare risk of blood clots after vaccination.
Studies show that protection against SARS-CoV-2 begins to decrease over time after initial vaccine doses. Additional vaccine doses (booster vaccinations) provide longer-lasting protection against COVID-19.
The FDA has authorized booster vaccinations of all three COVID-19 vaccines available in the United States. The eligibility period for a booster dose is based on several factors, including which vaccine you originally received and how long it has been since you were fully vaccinated.
Eligible people can choose which vaccine they receive as a booster dose — this is known as heterologous or “mix and match” dosing. Based on data from the National Institute of Allergy and Infectious Diseases, the FDA has determined that the benefits of mixing doses outweighs any known or potential risks.
Vaccines have very high safety standards, and COVID-19 vaccines are no exception. COVID-19 vaccines have undergone and will continue to undergo the most intensive safety monitoring in U.S. history.
The timeline for creating COVID-19 vaccines was shorter than for other vaccines for many reasons, including:
NIH scientists have been studying mRNA vaccines and coronaviruses for decades. They had a head start because they already knew a lot about how mRNA vaccines work and how to make them.
Researchers, the federal government, and drug companies came together like never before to cooperate and share resources, making the vaccine testing process more efficient.
NIH set up the COVID-19 Prevention Network (COVPN) to coordinate existing research networks and carry out large clinical trials in tens of thousands of people efficiently. Many Americans from diverse communities volunteered to participate in the studies.
The FDA analyzed data from the clinical trials right away.
The safety of the authorized COVID-19 vaccines is being tracked through the Vaccine Adverse Event Reporting System, a unique safety system called v-safe that was established specifically for COVID-19 vaccines, and other systems. Vaccine manufacturers submit monthly safety updates to the FDA. The FDA also inspects vaccine production facilities and checks the quality of vaccine batches.
Studies show that COVID-19 vaccines are very effective in preventing COVID-19, even for people at high risk for the disease.
Sometimes people who are fully vaccinated get a breakthrough infection, meaning that they test positive for SARS-CoV-2 or become ill with COVID-19. Fully vaccinated people are less likely to become seriously ill, even from COVID-19 variants.
All vaccines may cause some side effects, which are normal signs that your body is making antibodies. These side effects go away in a few days. Many people have no side effects.
Serious side effects that could cause long-term health problems are extremely unlikely following any vaccination, including COVID-19 vaccination. These rare side effects usually appear within six weeks of receiving a vaccine dose. If you have any health problems after vaccination, report them to the Vaccine Adverse Event Reporting System (VAERS).
Rare cases of heart inflammation have been reported after mRNA COVID-19 vaccination, mainly in male adolescents and young adults.
The CDC continues to recommend vaccination for everyone 12 years of age and older, given the greater risk of serious complications related to COVID-19.
The federal government is providing FDA-authorized COVID-19 vaccines free to all people living in the United States, regardless of their immigration or health insurance status. Search vaccines.gov, text your ZIP code to 438829, or call 1-800-232-0233 to find COVID-19 vaccine locations near you. Contact your state health department to find additional vaccination locations in your area.
If you have difficulty reaching a vaccination site, you may be able to get an in-home vaccination. Check a list of services that may offer in-home COVID-19 vaccinations in your area.
Studies and current data show that the antibodies our bodies make after vaccination recognize and protect against COVID-19 variants. This is being closely investigated, and more studies are underway.
The rise of these variants is a reminder that as long as SARS-CoV-2 continues to spread, it has the potential to evolve into new variants. Widespread vaccination will help reduce the rise of additional variants.
Children and teens age 5 and older can now get the Pfizer COVID-19 vaccine. It is currently the only COVID-19 vaccine authorized for people younger than 18. However, clinical trials are underway to test the safety and effectiveness of all currently available vaccines in younger children. Experts how that vaccines for these age groups will be authorized by late 2021.
Studies indicate that vaccination produces a stronger immune response than the one produced by COVID-19 infection. The benefits of vaccination after infection far outweigh any known or potential risks.
To ensure that people who recover from COVID-19 are protected from getting the disease again, the CDC recommends that they get vaccinated. The timing of vaccination depends on when a person had COVID-19 and whether and when they received treatment. If you have had COVID-19 and want to be vaccinated, talk to your doctor about when you should get the vaccine.
New and ongoing studies on vaccines are underway. NIH Institutes and Centers, in partnership with private businesses, continue to study different types of vaccines.
Some current research aims to determine whether approved vaccines will grant immunity against emerging COVID-19 variants and whether new vaccines will be needed. Other vaccine studies continue to monitor the health of people who have already had a vaccine to determine their effectiveness over a longer period of time.
NIH has begun a clinical trial to assess the antibody response to an extra dose of an authorized or approved COVID-19 vaccine in people with autoimmune disease who did not respond to an original COVID-19 vaccine regimen. The trial also will investigate whether pausing immunosuppressive therapy for autoimmune disease could improve the antibody response for people who are receiving that additional vaccine dose.
COVID-19 Vaccine Resources
HHS shares information about the vaccine distribution process.
The CDC shares information to answer common questions about vaccine safety.
Learn what to expect when you volunteer for a vaccine clinical trial.
Get the facts about COVID-19 vaccine studies.