Millions of Americans have received a both doses of the Pfizer and Moderna mRNA vaccines, with the vast majority experiencing minor, temporary side effects. As an additional layer of checks and balances, an external advisory board made up of medical and research professionals using additional public health data have reviewed final COVID-19 vaccine data and recommended the Pfizer, Moderna and Janssen vaccines be made available for emergency use.

America’s best medical and research professionals have been working for years on coronavirus vaccines for SARS and MERS. SARS and MERS are different than COVID-19 but belong to the coronavirus family. The lessons learned through those developments are being applied today. Specifically, the effort to develop a COVID-19 vaccine began more than one year ago.

Clinical trials are an important part of determining vaccine safety and efficacy. Pfizer, Moderna and Janssen have completed Phase 3 clinical trials involving tens of thousands of participants. The purpose of clinical trials is to generate scientific data and other information for the Food and Drug Administration to review and base their recommendations on.

Vaccine safety monitoring systems are in place to collect side effect data. If an unexpected adverse event is seen, experts quickly study it further to assess whether it is a true safety concern. Experts then decide whether changes are needed in U.S. vaccine recommendations. This monitoring is critical to help ensure that the benefits continue to outweigh the risks for people who receive vaccines.

Although the timeline has been accelerated, it doesn’t mean we skipped the integrity of the trial and approval processes. Scientists have had a jump on developing the COVID-19 vaccine, using their experience from previous coronavirus vaccine efforts. Another way scientists preserved safety and saved time was by working on efforts simultaneously, rather than one after another like the traditional process. For example, COVID-19 vaccines were in Phase III clinical trials at the same time they were being manufactured. When it was proven safe and effective, the manufactured vaccines were deployed. If the vaccines don’t pass the approval process, which is verified by an independent committee of health experts, the unproven vaccines won’t be used.

You should delay your vaccination if you have had a known SARS-CoV-2 (virus that causes COVID-19) exposure until your quarantine period has ended, unless residing in a congregate setting (health care/long-term care facility, correctional facility, homeless shelter, etc.).

Routine testing for pregnancy or antibody tests is not recommended in relation to vaccine use.

There is no information on co-administration of this COVID-19 vaccine with other vaccines. The COVID-19 vaccines should be spaced at least 14 days from any other vaccine.

Yes, patients must receive the same vaccine for both the first and second doses of Pfizer or Moderna. Your vaccination provider will give you a vaccine card stating the manufacturer name and other critical information you will need for a second dose.

While vaccine supply is still very limited, it is also important to return to the same provider/location for your second dose.

Pfizer’s vaccine was approved for those age 16 and older. Moderna and Janssen's vaccines have been approved for those 18 and older.

The Pfizer and Moderna vaccines are not recommended for individuals who have experienced a serious reaction (e.g., anaphylaxis) to a prior dose of a COVID-19 vaccine or to any of its components. Those who have had a severe allergic reaction to any ingredient of the Janssen vaccine should not receive the Janssen vaccine. For information on vaccine components, refer to the manufacturers’ package inserts from Pfizer, Moderna, and Janssen.

The ingredients used in the mRNA vaccines developed by Pfizer and Moderna are simple. They contain mRNA, as well as lipids to ensure safe delivery of the mRNA that will initiate an immune response.

Ingredients of the Janssen COVID-19 vaccine include: recombinant, replication-incompetent adenovirus type 26 expressing the SARS-CoV-2 spike protein, citric acid monohydrate, trisodium citrate dihydrate, ethanol, 2-hydroxypropyl-β-cyclodextrin (HBCD), polysorbate-80, sodium chloride.

Although FDA approved adjuvants (aluminum salts) and preservatives (ethlymercury) have a history of safe use in vaccines, they were not used by Pfizer, Moderna or Janssen.

After getting vaccinated, you might have some side effects, which are normal signs that your body is building protection. Common side effects are pain, redness, and swelling in the arm where you received the shot, as well as tiredness, headache, muscle pain, chills, fever, and nausea throughout the rest of the body. These side effects could affect your ability to do daily activities, but they should go away in a few days. Learn more about what to expect after getting a COVID-19 vaccine.

No. Every day, a healthy immune system successfully fights off thousands of germs. Antigens are parts of germs that cause the body’s immune system to go to work to build antibodies, which fight off diseases. The antigens in vaccines come from the germs themselves, but the germs are weakened or killed so they cannot cause serious illness. Even if people receive several vaccinations in one day, vaccines contain only a tiny fraction of the antigens they encounter every day in their environment. Vaccines stimulate the immune system to produce antibodies to fight off serious vaccine-preventable diseases.

Pfizer’s clinical trial enrolled 44,000+ participants with 42% globally having racially and ethnically diverse backgrounds. Of Moderna’s 30,000 trial participants, 37% were from minority communities, including 6,000 Hispanic and 3,000 Black participants. Janssen’s trial included 43,783 participants in the United States, Latin America and South Africa. AstraZeneca’s initial trial data included participants from Brazil and the United Kingdom while the company continues to conduct trials in South Africa, Kenya, Latin America, Japan, Russia and the United States.

According to the CDC, people are considered fully vaccinated for COVID-19 ≥2 weeks after they have received the second dose in a 2-dose series (Pfizer-BioNTech or Moderna), or ≥2 weeks after they have received a single-dose vaccine (Johnson and Johnson (J&J)/Janssen ).†

The following recommendations apply to non-healthcare settings. For related information for healthcare settings, visit Updated Healthcare Infection Prevention and Control Recommendations in Response to COVID-19 Vaccination.

Fully vaccinated people can:

• Visit with other fully vaccinated people indoors without wearing masks or physical distancing
• Visit with unvaccinated people from a single household who are at low risk for severe COVID-19 disease indoors without wearing masks or physical distancing
• Refrain from quarantine and testing following a known exposure if asymptomatic
• Resume domestic travel and refrain from testing before or after travel or self-quarantine after travel.
• Refrain from testing before leaving the United States for international travel (unless required by the destination) and refrain from self-quarantine after arriving back in the United States.

For now, fully vaccinated people should continue to:

• Take precautions in public like wearing a well-fitted mask and physical distancing
• Wear masks, practice physical distancing, and adhere to other prevention measures when visiting with unvaccinated people who are at increased risk for severe COVID-19 disease or who have an unvaccinated household member who is at increased risk for severe COVID-19 disease
• Wear masks, maintain physical distance, and practice other prevention measures when visiting with unvaccinated people from multiple households
• Avoid medium- and large-sized in-person gatherings
• Get tested if experiencing COVID-19 symptoms
• Follow guidance issued by individual employers
• Follow CDC and health department travel requirements and recommendations

Updated on April 2, 2021. To ensure you are viewing the latest federal guidance, please click here. The CDC guidance will be updated and expanded based on the level of community spread of SARS-CoV-2, the proportion of the population that is fully vaccinated, and the rapidly evolving science on COVID-19 vaccines.

According to the CDC, people are considered fully vaccinated for COVID-19 ≥2 weeks after they have received the second dose in a 2-dose series (Pfizer-BioNTech or Moderna), or ≥2 weeks after they have received a single-dose vaccine (Johnson and Johnson (J&J)/Janssen ).†

The following recommendations apply to non-healthcare settings. For related information for healthcare settings, visit Updated Healthcare Infection Prevention and Control Recommendations in Response to COVID-19 Vaccination.

Fully vaccinated people can:

• Visit with other fully vaccinated people indoors without wearing masks or physical distancing
• Visit with unvaccinated people from a single household who are at low risk for severe COVID-19 disease indoors without wearing masks or physical distancing
• Refrain from quarantine and testing following a known exposure if asymptomatic
• Resume domestic travel and refrain from testing before or after travel or self-quarantine after travel.
• Refrain from testing before leaving the United States for international travel (unless required by the destination) and refrain from self-quarantine after arriving back in the United States.

For now, fully vaccinated people should continue to:

• Take precautions in public like wearing a well-fitted mask and physical distancing
• Wear masks, practice physical distancing, and adhere to other prevention measures when visiting with unvaccinated people who are at increased risk for severe COVID-19 disease or who have an unvaccinated household member who is at increased risk for severe COVID-19 disease
• Wear masks, maintain physical distance, and practice other prevention measures when visiting with unvaccinated people from multiple households
• Avoid medium- and large-sized in-person gatherings
• Get tested if experiencing COVID-19 symptoms
• Follow guidance issued by individual employers
• Follow CDC and health department travel requirements and recommendations

Updated on April 2, 2021. To ensure you are viewing the latest federal guidance, please click here. The CDC guidance will be updated and expanded based on the level of community spread of SARS-CoV-2, the proportion of the population that is fully vaccinated, and the rapidly evolving science on COVID-19 vaccines.

The initial clinical trials did not include children. Pfizer’s vaccine has been authorized for emergency use to vaccinate those aged 16 and up. Moderna and Janssen's vaccines have been authorized for emergency use to vaccinate those ages 18 and up.

Yes, if you are pregnant, you might choose to be vaccinated. Based on how COVID-19 vaccines work, experts think they are unlikely to pose a specific risk for people who are pregnant. However, there are currently limited data on the safety of COVID-19 vaccines in pregnant people because these vaccines have not been widely studied in pregnant people. Systems are in place to continue to monitor vaccine safety, and so far, they have not identified any specific safety concerns for pregnant people. Clinical trials to evaluate the safety and efficacy of COVID-19 vaccines in pregnant people are underway or planned.

You might want to have a conversation with your healthcare provider to help you decide whether to get vaccinated. While a conversation with your healthcare provider might be helpful, it is not required before to vaccination. Learn more about vaccination considerations for people who are pregnant or breastfeeding.

If you are pregnant and have received a COVID-19 vaccine, we encourage you to enroll in v-safe, CDC’s smartphone-based tool that provides personalized health check-ins after vaccination. A v-safe pregnancy registry has been established to gather information on the health of pregnant people who have received a COVID-19 vaccine.

States are required to verify that the vaccinators have licenses for the states they will be vaccinating in and that they are in good standing. The Bureau of Immunizations within DHSS will verify licenses utilizing professional boards of registration.

According to Dr. Anthony Fauci, the overwhelming majority of people who are infected by SARS-CoV-2, the virus that causes COVID-19, recover. That means most patients’ immune response that’s adequate to suppress the virus and eliminate it from their body. That gives medical professionals confidence that a vaccine could initiate a similar response.

We also had a jumpstart on the development of this vaccine. America’s best medical and research professionals have been working for years on coronavirus vaccines for SARS and MERS. SARS and MERS are different than SARS-CoV-2 but belong to the coronavirus family. The lessons learned through those developments are being applied today. Specifically, the effort to develop a COVID-19 vaccine began months ago.

At this time, the CDC does not recommend taking pain relievers before a COVID-19 vaccination appointment because there is not enough information to determine the impact the medications may have on the immune response. However, they may be used post-vaccination to ease discomfort.

No. While experts learn more about the protection that COVID-19 vaccines provide under real-life conditions, it will be important for everyone to continue using all the tools available to us to help stop this pandemic, like covering your mouth and nose with a mask, washing hands often, and staying at least 6 feet away from others. Together, COVID-19 vaccination and following CDC’s recommendations for how to protect yourself and others will offer the best protection from getting and spreading COVID-19.

COVID-19 is a deadly disease that causes severe illness – and in some cases, long term symptoms that we have yet to fully understand. The COVID-19 vaccine candidates have been created to decrease death and severe illness.

Although a high percentage of people recover from COVID-19, some are hospitalized and experience severe illness. It is also somewhat common to have the virus but never experience symptoms, and it is possible to spread the virus to others even when symptoms are not present. When you make the choice to be vaccinated, you are protecting not only you but also those around you from the chance of death and severe illness caused by COVID-19.

Both the Pfizer and Moderna vaccines have an approximate 95% efficacy rate and are highly effective in preventing severe disease. In December, the CDC published that the Pfizer and Moderna vaccines had a constant efficacy rate across age, sex and ethnicity categories, as well as among individuals with underlying medical conditions and those who have been previously infected by SARS-CoV-2. Additionally, initial clinical data showed protection is achieved 28 days after the initiation of the Pfizer vaccine, which consists of a 2-dose schedule.

According to Moderna's website, initial trial data was used to estimate a vaccine efficacy of 94.5%. Initial data from Moderna also shows the vaccine may provide some protection against asymptomatic SARS-CoV-2 infection.

AstraZeneca estimates a 90% efficacy rate from a specific 2-dose schedule.

Janssen’s clinical trials showed an 85% efficacy rate in preventing hospitalization and complete protection against death caused by SARS-CoV-2.

All authorized vaccines are highly effective. The different types of vaccines were not studied in head-to-head comparisons or trials; therefore, they should not be compared to each other.

Initial data from Moderna shows the vaccine may provide some protection against asymptomatic SARS-CoV-2 infection.

There is no definitive data on how long immunity will last with a vaccine. A COVID-19 vaccine will trigger an immune system response to develop active immunity. Active immunity results when exposure to a disease organism triggers the immune system to produce antibodies to that disease. If an immune person comes into contact with that disease in the future, their immune system will recognize it and immediately produce the antibodies needed to fight it. Although we don't know exactly how long immunity will last for the specific vaccines in trial, active immunity can be long-lasting.

Two of the three COVID-19 vaccines approved for use require two doses. Janssen’s vaccine requires one dose.

It is important that patients return for the second dose to develop the highest level of protection from SARS-CoV-2. Patients who do not receive the second Pfizer vaccination dose at 21 days or the Moderna vaccination at 28 days should still receive that second dose as soon as possible thereafter.

A vaccine is necessary to help you and your community shape a new normal. Stopping a pandemic requires using all the tools available. Vaccines boost your immune system so it will be ready to fight the virus if you are exposed. Other steps, like masks and social distancing, help reduce your chance of being exposed to or spreading the virus.

Yes. We are seeing evidence of reinfection in patients. Early evidence suggests natural immunity from SARS-CoV-2 may not last very long, but more studies are needed to better understand this. Vaccination should not occur until the patient has met criteria to discontinue isolation.

Patients who do not receive the second vaccination dose at 21 days for Pfizer or 28 days for Moderna should still receive that second dose as soon as possible thereafter. However, if it is not feasible to adhere to the recommended interval and a delay in vaccination is unavoidable, the second dose of Pfizer-BioNTech and Moderna COVID-19 vaccines may be administered up to 6 weeks (42 days) after the first dose. There are currently limited data on efficacy of mRNA COVID-19 vaccines administered beyond this window. If the second dose is administered beyond these intervals, there is no need to restart the series.

Scientists are working to learn more about these variants to better understand how easily they might be transmitted and whether currently authorized vaccines will protect people against them; however, early evidence suggests the vaccines remain effective against the variant. Currently, there is no evidence that these variants cause more severe illness or increased risk of death. New information about the virologic, epidemiologic, and clinical characteristics of these variants is rapidly emerging. The Missouri State Public Health Laboratory, in collaboration with the CDC, is monitoring the situation closely.

Antibody testing is not currently recommended to assess for immunity to COVID-19 following COVID-19 vaccination or to assess the need for vaccination in an unvaccinated person. Since vaccines induce antibodies to specific viral protein targets, post-vaccination serologic test results will be negative in persons without history of previous natural infection if the test used does not detect antibodies induced by the vaccine.