Vaccines protect people from specific diseases by training the immune system to recognize and attack a virus before it can make them sick.

Watch this series of videos from Health Action Alliance to better understand how vaccines work.

Vaccines also protect the community. When most of a population is immune to an infectious disease, people who are not immune are also protected because it is harder for the disease to spread. This also makes it harder for the virus to mutate.

Diseases that were once common in the U.S. – like measles, mumps and polio – are now very rare because most Americans have immunity through vaccines.

Vaccines must go through many tests and approval processes to make sure they are effective and safe before they are distributed to the public.

Vaccines usually go through six stages of development. During these stages, the vaccines being studied are called “candidates.”

1. Exploratory Stage
2. Pre-Clinical Stage
3. Clinical Trials – Phase 1, Phase 2, Phase 3
4. Manufacturing
5. Regulatory Review and Approval
6. Quality Control

To speed up the process for COVID-19 vaccines, some of these stages took place at the same time. For example, drug companies may begin making a vaccine while it is still in Phase 3 clinical trials so that the vaccine is ready to distribute immediately if it is approved.

Emergency use authorization (EUA) allows the FDA to authorize the use of yet-to-be-approved drugs, or unapproved uses of approved drugs, often in emergency situations when there are no other prevention or treatment options. The FDA issued EUAs for the Pfizer, Moderna, and Johnson & Johnson vaccines, and has now issued full approval for the Pfizer COVID-19 vaccine.

In an emergency when lives are at risk, like a pandemic, it may not be possible to gather all the evidence that the FDA would usually require before approving a vaccine or drug. If evidence strongly suggests patients have benefited from a treatment, the FDA can issue an EUA to make it available to the public. For the COVID-19 vaccines, the FDA required two months of safety and efficacy data before the EUA was granted, including clinical trials with tens of thousands of people and rigorous testing and review. Compared to EUA, full FDA approval of vaccines requires even more data on safety, manufacturing, and effectiveness over longer periods of time. All the vaccines continue to be closely monitored.

The Pfizer COVID-19 vaccine was the first vaccine to have the necessary data to receive EUA, and it was the first to have enough data to receive full approval. Moderna has also submitted an application for full approval of its COVID-19 vaccine, and the FDA is currently reviewing those data. For the time being, the Moderna and Johnson & Johnson vaccines will continue to be safely administered through emergency use authorization.

All Missourians five years old or older can get a free COVID vaccine. There are multiple options for where you can get vaccinated, including local public health departments, hospitals, health care clinics and pharmacies. Find a vaccine

There are multiple agencies responsible for making sure new vaccines are safe. Before a vaccine becomes available, it must go through several rounds of tests with human volunteers. The FDA reviews the results of these studies before authorizing vaccines. The FDA also inspects the factories where vaccines are produced to ensure quality and safety.

Once a vaccine is released, agencies in the national vaccine monitoring system continue to oversee the safety of vaccines. These agencies monitor the safety of hundreds of millions of vaccines every year and include:

• Vaccine Adverse Events Reporting System (VAERS)
• The Vaccine Safety Datalink (VSD)
• Post-licensure Rapid Immunization Safety Monitoring System (PRISM)
• Clinical Immunization Safety Assessment Project (CISA)
• The Department of Defense (DoD)
• U.S. Department of Veterans Affairs (VA)
• National Institutes of Health (NIH)
• Office of Infectious Disease and HIV/AIDS Policy (OIDP)

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The Pfizer vaccine is available and recommended for everyone five years old and older. The Moderna and Johnson & Johnson vaccine are authorized for people 18 and older. Research on COVID vaccines for younger children is ongoing.

The Pfizer and Moderna vaccines both require two shots. The Johnson & Johnson vaccine requires a single dose.

Booster doses are recommended for some groups of people:

• Some Pfizer and Moderna recipients should get a booster at least six months after their second shot – people age 65 and older, and adults at high risk due to medical conditions or exposure at their jobs.
• All Johnson & Johnson recipients age 18 and older should get a booster at least two months after their initial shot.
• Immunocompromised people who received the Pfizer or Moderna vaccine should get an additional dose at least 28 days after their second dose.

The CDC’s clinical guidance advises people to get the same booster as their initial vaccine, but allows people to mix and match vaccines. This means they can choose to get a different brand of COVID-19 vaccine for their booster than they receieved for their initial dose.

As the science and the virus evolve, so do policies and recommendations.

Booster doses are common for many vaccines. The scientists and medical experts who developed the COVID-19 vaccines continue to closely watch for signs of weakening immunity, how well the vaccines protect against new strains of the virus, and how data differ across age groups and risk factors.

Side effects are a normal part of vaccination. After getting a vaccine, the body launches an immune response that can produce short-term symptoms. These symptoms are a positive sign that the body is building immunity. During clinical trials for COVID-19 vaccines, some participants reported side effects including exhaustion or tiredness, muscle pain, chills, and fever. These symptoms were more common after the second dose of the vaccine and usually last for one or two days. These side effects do not mean that you are sick with COVID-19.

The potential side effects of a vaccine are much less serious than the long-term, life-threatening symptoms of COVID-19. Talk with your healthcare provider about any worries you may have about the vaccine and how you will handle potential side effects. Source 1, Source 2, Source 3, Source 4

While COVID-19 vaccines are highly effective, no vaccine provides 100% immunity. Because COVID-19 is a new virus, scientists and medical experts continue to monitor how long immunity lasts, whether some groups may need additional doses, and how well the vaccines protect against new variants of the virus.

Data continue to show that the COVID-19 vaccines are extremely effective in protecting fully vaccinated people from catching and spreading the virus, including the delta variant. A small percentage of vaccinated people experience breakthrough cases, but they are much more likely to have milder symptoms than unvaccinated people with COVID-19.

Unvaccinated people continue to account for the vast majority of severe cases, hospitalizations, and deaths from COVID-19. CDC data show that in August 2021, the risk of dying from COVID-19 in the U.S. was more than 11 times greater for unvaccinated people compared to fully vaccinated people.

The risk of severe illness from COVID-19 is increased for some groups — including older adults, people with underlying medical conditions, immunocompromised people, and pregnant or recently pregnant people. If you have questions about your risk of COVID-19, how to protect yourself from COVID-19, or about the vaccines, speak to your health provider.

Source 1, Source 2

Johnson & Johnson clinical trials showed their vaccine protected against several emerging variants. Research shows Pfizer’s COVID-19 vaccine offers protection against 2021 strains of coronavirus. Ongoing testing will be done to gauge the vaccines’ protection against developing srains of the virus.

COVID-19 is a relatively new virus in humans. We don’t know yet know long immunity from infection or vaccination will last. Some people have been infected with COVID-19 more than once, which shows that immunity from natural infection may not last very long. Immunity from the vaccine is expected to last longer, but researchers will need to continue studying this question. Source 1, Source 2

Vaccines are an important tool in ending the pandemic and allowing vaccinated individuals safely return to normal activities. While a growing number of people are getting vaccinated, it could take while for enough people to get vaccinated so that we achieve “herd immunity” and can stop the spread of the virus. In the meantime, we need to continue taking safety steps like frequent handwashing, wearing face masks, and physical distancing to prevent to protect ourselves, our families and people in our communities. Source 1, Source 2

Technically, yes. States have the legal and constitutional power to introduce a vaccination mandate requiring people who live in the state to be vaccinated. Upon full approval from the FDA, states could make COVID-19 vaccination a requirement before returning or accessing workplaces, schools and colleges. Missouri Governor Mike Parson has said he will not require vaccinations in Missouri. Source 1, Source 2

Yes. According to the U.S. Equal Employment Opportunity Commission (EEOC), workplaces can require that employees get the COVID-19 vaccine. Employees may request an exemption due to a disability or religious reason. Employers may put in place requirements such as frequent testing, as an alternative to vaccination.

The Pfizer-BioNTech vaccine is approved for children 5 years old and older, and the Moderna and AstraZeneca vaccines are authorized for those 18 and older. Trials for children under the age of 5 are underway.

There is a lot of new information – and sometimes untrue information – about the vaccines, and it can be hard to know who to turn to for advice.

It is best to talk with a healthcare professional, like your doctor, who has the scientific knowledge to answer your questions and who has your family’s best interests in mind. Download a discussion guide to help with this conversation here.

Other sources of reliable information about the vaccines include your local public health department, the CDC, the FDA, and professional associations like the American Academy of Pediatrics.