Moderna COVID-19 Vaccine Questions
Below are answers to commonly asked clinical questions about Moderna COVID-19 Vaccine. Get answers to other frequently asked questions:
Moderna COVID-19 Vaccine is authorized and recommended for people 18 years of age and older.
All people for whom vaccination is indicated should receive 2 doses 28 days apart. Do not schedule vaccine recipients to receive the second dose earlier than the recommended interval.
Second doses of Moderna COVID-19 Vaccine administered up to 4 days before the recommended date (4-day grace period) are considered valid. This means that when reviewing records, a second dose of Moderna COVID-19 Vaccine administered 24 or more days after the first dose is considered valid.
You should schedule the second dose of Moderna COVID-19 Vaccine 28 days after the first dose (the recommended interval). Do not use the 4-day grace period when scheduling appointments. Appointments for a second dose should be scheduled to meet the recommended interval.
If a dose is inadvertently administered before the 4-day grace period, it does not need to be repeated. This means that when reviewing records, a second dose of Moderna COVID-19 Vaccine administered 23 or less days after the first dose does not need to be repeated. This is considered a vaccine administration error. Determine how the error occurred and implement strategies to prevent it from happening again. Additionally, you are required to report COVID-19 vaccine administration errors to the Vaccine Adverse Event Reporting System (VAERSexternal icon).
No, the grace period cannot be used to schedule second doses. Administer doses as close to the 28-day interval as possible, but not earlier than recommended. The grace period should be used only for retrospectively reviewing records. If it is discovered a dose has been inadvertently administered within a grace period of ≤4 days from the recommended date for the second dose (i.e., 24–27 days after dose 1), the dose is considered valid.
You should administer the second dose as close as possible to the recommended interval of 28 days after dose 1. However, if it is not possible to follow the recommended interval, you may schedule the second dose of the Moderna COVID-19 Vaccine for administration up to 6 weeks (42 days) after the first dose. There are currently limited data on effectiveness of mRNA COVID-19 vaccines administered beyond this window. If the second dose is administered after these intervals, there is no need to restart the series.
CDC does not recommend that providers hold back stock for a second dose after administering a patient’s first dose. You should inform the patient that they need to return for the second dose.
COVID-19 vaccines are not interchangeable. The safety and effectiveness of a mixed-product series have not been evaluated. Therefore, make every effort to determine which vaccine product was administered as the first dose to ensure your patient completes the vaccine series with the same product. In exceptional situations:
- When the vaccine product given for the first dose cannot be determined or is no longer available, you may administer any available mRNA COVID-19 vaccine, with a minimum of 28 days between doses.
If a patient received the first dose of an mRNA COVID-19 vaccine but is unable to complete the series with either the same or a different mRNA COVID-19 vaccine (e.g., due to contraindication), you may consider administering a single dose of Janssen COVID-19 Vaccine, with a minimum of 28 days between doses. See contraindications and precautions for more information on use of Janssen COVID-19 Vaccine and additional precautions in people with a contraindication to mRNA COVID-19 vaccines.
Use the following strategies to help ensure patients receive the second dose with the appropriate product and interval between doses:
- Provide a COVID-19 vaccination record card to every vaccine recipient. Ask recipients to bring their card to their appointment for the second dose. Encourage them to make a backup copy (e.g., by taking a picture of the card with their phone).
- Encourage vaccine recipients to enroll in v-safe, a free smartphone-based tool that uses text messaging and web surveys to provide personalized health check-ins as well as second-dose reminders.
- Encourage vaccine recipients to enroll in VaxTextSM, a free text-message-based platform, to receive reminders to get their second dose of COVID-19 vaccine.
- Record each recipient’s vaccination in the immunization information system (IIS).
- Record vaccine administration information in the patient’s medical record.
- Make an appointment for the second dose before the vaccine recipient leaves to increase the likelihood that patients will return to the same vaccination provider site for the second dose. Make sure that the recipient has a reminder for the second appointment.
No. When the same mRNA vaccine product is temporarily unavailable, it is preferable to delay the second dose up to 6 weeks following the first dose to administer the same product rather than administer a mixed series using a different product.
Learn more about interchangeability of COVID-19 vaccine products.
No. You may administer a COVID-19 vaccine and other vaccines without regard to timing. This includes simultaneous administration of a COVID-19 vaccine and other vaccines (including live, attenuated vaccines such as the measles-mumps-rubella [MMR] vaccine) on the same day, as well as coadministration at any time interval. It is unknown whether reactogenicity of a COVID-19 vaccine is increased with coadministration, including with other vaccines known to be more reactogenic, such as adjuvanted vaccines or live vaccines.
When deciding whether to coadminister other vaccines with a COVID-19 vaccine, consider:
- Whether the patient is behind or at risk of becoming behind on recommended vaccines
- The patient’s risk of vaccine-preventable disease (e.g., during an outbreak or occupational exposures)
- The reactogenicity profile of the vaccines
Learn more about coadministration with other vaccines.
Yes. CDC recommends COVID-19 vaccination for all people with prior COVID-19 infection. However, the timing of the vaccination depends on when a person had SARS-CoV-2 infection and/or when they received treatment.
People with a prior infection: Offer vaccination regardless of history of prior symptomatic or asymptomatic SARS-CoV-2 infection, including to people with prolonged post–COVID-19 symptoms.
While there is no recommended minimum interval between infection and vaccination, current evidence suggests that the risk of SARS-CoV-2 reinfection is low in the months after initial infection but may increase with time due to waning immunity.
People with a history of multisystem inflammatory syndrome in adults (MIS-A): These people may choose to be vaccinated, but should consider delaying vaccination until they have recovered from their illness and for 90 days after the date of diagnosis. Considerations for vaccination may include:
- Clinical recovery from MIS-A, including return to normal cardiac function
- Personal risk of severe acute COVID-19 (e.g., age, underlying conditions)
- Level of COVID-19 community transmission and personal risk of reinfection
- Lack of safety data of COVID-19 vaccines following these illnesses
- Timing of any immunomodulatory therapies
People with a current infection: Defer vaccination of people with known current SARS-CoV-2 infection until the person has recovered from acute illness (if the person has symptoms) and until criteria have been met for them to discontinue isolation. This recommendation applies to any vaccine, including the first and second doses of COVID-19 vaccine.
For people who previously received passive antibody therapy as part of COVID-19 treatment, defer vaccination for at least 90 days after receipt of passive antibody therapy (monoclonal antibodies or convalescent plasma). This recommendation applies to people who receive passive antibody therapy before receiving any COVID-19 vaccine dose and to those who receive passive antibody therapy after the first dose of an mRNA COVID-19 vaccine but before the second dose, in which case the second dose should be deferred for at least 90 days following receipt of the antibody therapy.
Learn more about COVID-19 vaccination and SARS-CoV-2 infection.
No. Your patient may be vaccinated without waiting 90 days. Although people who have received passive antibody therapy as treatment for COVID-19 should wait at least 90 days before vaccination, there is no minimum interval between antibody therapies not specific to COVID-19 treatment and COVID-19 vaccination.
Yes. You may administer any currently authorized or approved COVID-19 vaccine to people with underlying medical conditions; the Advisory Committee on Immunization Practices (ACIP) does not state a product preference. This includes people with:
- Immunocompromising conditions or people who take immunosuppressive medication or therapies (For guidance on additional dose recommendations of an mRNA COVID-19 vaccine for immunocompromised persons, please visit https://www.cdc.gov/vaccines/covid-19/hcp/immunocompromised-patients.html and https://www.cdc.gov/vaccines/covid-19/clinical-considerations/immunocompromised.html.)
- Autoimmune conditions
- A history of Guillain-Barré syndrome
- A history of Bell’s palsy
- A history of dermal filler use
Learn more about vaccinating patients with underlying medical conditions.
As with other vaccines, a moderate or severe illness is a precaution to receiving any currently authorized or approved COVID-19 vaccine. It is not considered a contraindication. Generally, vaccination should be delayed until the acute illness has improved. However, if you and your patient feel the potential benefits of vaccination outweigh the potential risks, they may receive COVID-19 vaccine.
The following considerations can be used to help the provider conduct a risk assessment for COVID-19 vaccination:
- Risk of exposure to SARS-CoV-2 (e.g., living in a congregate setting, such as a long-term care facility; occupation)
- Risk of severe disease or death due to COVID-19 (e.g., because of age or underlying medical conditions)
- Whether the patient has previously been infected with SARS-CoV-2 and, if so, how long ago
- Note: Vaccination is recommended for people with a history of COVID-19; however, because the risk for reinfection is low in the months after initial infection, people with a precaution to vaccination and who have had a recent SARS-CoV-2 infection may choose to delay vaccination.
Yes. CDC recommends COVID-19 vaccination for all people who are pregnant, breastfeeding, trying to get pregnant now, or who might become pregnant in the future. Pregnant or breastfeeding people are eligible for and can receive any of the currently FDA-authorized or FDA-approved COVID-19 vaccines; ACIP does not state a product preference.
However, you should talk to pregnant, breastfeeding, and postpartum people younger than 50 years old who choose to receive Janssen COVID-19 Vaccine about:
- The rare but increased risk of thrombosis with thrombocytopenia syndrome (TTS) after receipt of this vaccine
- The availability of other FDA-authorized or approved COVID-19 vaccines (i.e., mRNA vaccines) for which the risk of TTS has not been observed
Pregnant people with COVID-19 are at increased risk for preterm birth and might be at increased risk for other adverse pregnancy complications and outcomes, such as preeclampsia, coagulopathy, and stillbirth. Additionally, pregnant people with COVID-19 are at increased risk for severe illness when compared with non-pregnant people, including illness that requires hospitalization, intensive care unit admission, mechanical ventilation, or extracorporeal membrane oxygenation.
A growing body of evidence on the safety and effectiveness of COVID-19 vaccination – in both animal and human studies – indicates that the benefits of vaccination outweigh any known or potential risks of COVID-19 vaccination during pregnancy, including:
- No safety signals in animal studies
- No adverse outcomes in previous trials of the adenovirus platform that included pregnant people
- No evidence of COVID-19 vaccines causing infection in the pregnant person or the fetus
If a person becomes pregnant following the first dose of a COVID-19 vaccine that requires two doses (i.e., Pfizer-BioNTech COVID-19 Vaccine or Moderna COVID-19 Vaccine), the second dose should be administered as indicated for the person to have maximum protection.
Encourage pregnant people who get vaccinated to enroll in v-safe, a smartphone-based tool that uses text messaging and web surveys to provide personalized health check-ins after COVID-19 vaccination. A v-safe pregnancy registry has been established to follow outcomes among pregnant people who are vaccinated.
Learn more about vaccination of pregnant or breastfeeding people.
Administer the second dose of Moderna COVID-19 vaccine 28 days after the first dose. The second dose may be administered up to 6 weeks (42 days) after the first dose, even though it may not be at least 90 days since the passive antibody therapy.
Myocarditis is inflammation of the heart muscle, and pericarditis is inflammation of the outer lining of the heart. In both cases, the body’s immune system causes inflammation in response to an infection or some other trigger. Symptoms can include chest pain, shortness of breath, or palpitations.
The severity of cases of myocarditis and pericarditis can vary. For the cases reported after mRNA COVID-19 vaccination, most who presented to medical care have responded well to medications and rest.
The ACIP COVID-19 Vaccines Work Group reviewed:
- Clinical trial and post-authorization safety data for myocarditis/pericarditis after receipt of mRNA COVID-19 vaccines
- A risk-benefit assessment of myocarditis after receipt of mRNA COVID-19 vaccines
On June 23, 2021, after reviewing available evidence, ACIP determined that the benefits of using mRNA COVID-19 vaccines under the FDA’s Emergency Use Authorization (EUA) clearly outweigh the risks of myocarditis/pericarditis in all populations, including adolescents and young adults.
Yes. People who have a history of myocarditis or pericarditis unrelated to mRNA COVID-19 vaccination may receive any FDA-authorized or approved COVID-19 vaccine after the episode of myocarditis or pericarditis has completely resolved. This includes resolution of symptoms attributed to myocarditis or pericarditis, as well as no evidence of ongoing heart inflammation or sequelae as determined by the person’s clinical team, which may include a cardiologist, and special testing to assess cardiac recovery.
No. A person is considered fully vaccinated against COVID-19 2 or more weeks after receipt of the second dose in a 2-dose series (Pfizer-BioNTech and Moderna) or 2 or more weeks after receipt of the single dose of the Janssen vaccine. A person who only receives one dose of a 2-dose mRNA COVID-19 vaccine series is not considered fully vaccinated.
It is unclear if people who developed myocarditis or pericarditis after a first dose of an mRNA COVID-19 vaccine may be at increased risk of further adverse cardiac effects following a second dose of the vaccine. Until additional safety data are available, experts recommend that people who develop myocarditis or pericarditis after a first dose of an mRNA COVID-19 vaccine defer receiving the second dose. People with a history of myocarditis or pericarditis who choose to receive the second dose of an mRNA COVID-19 vaccine should wait at least until their initial episode of myocarditis or pericarditis has completely resolved. Decisions about proceeding with the second dose of an mRNA vaccine should include a conversation between the patient, their parent, guardian, or caregiver (when relevant), and their clinical team.
Although myocarditis/pericarditis after mRNA COVID-19 vaccination can occur in both men and women, more cases have been reported in men in younger age groups. Consider myocarditis and pericarditis in adolescents or young adults with acute chest pain, shortness of breath, or palpitations. Ask about prior COVID-19 vaccination if you identify these symptoms, as well as relevant other medical, travel, and social history. For more information, please refer to Myocarditis and Pericarditis Following mRNA COVID-19 Vaccination.
Based on data from VAERS, confirmed cases have typically occurred within several days after COVID-19 vaccination.
Contraindications to vaccination with Moderna COVID-19 Vaccine include
- Severe allergic reaction (e.g., anaphylaxis) after a previous dose or to a component of an mRNA COVID-19 vaccine (Moderna or Pfizer-BioNTech)
- Immediate allergic reaction of any severity to a previous dose or known (diagnosed) allergy to a component of the vaccine (see Appendix C for a list of vaccine components)
Do not vaccinate people with a contraindication. Consider referral to an allergist-immunologist or administering a different COVID-19 vaccine. You may consider Janssen COVID-19 Vaccine for people with a contraindication to mRNA COVID-19 vaccines (including a contraindication due to a known polyethylene glycol [PEG] allergy). People with a contraindication to mRNA COVID-19 vaccines have a precaution to Janssen COVID-19 Vaccine. In these cases, consider consultation with an allergist-immunologist to help determine if the patient can safely receive vaccination. Healthcare providers and health departments may also request a consultation from the Clinical Immunization Safety Assessment COVIDvax Project. Vaccination of these people should only be done in an appropriate setting under the supervision of a healthcare provider experienced in the management of severe allergic reactions. People who have received one mRNA COVID-19 vaccine dose but for whom the second dose is contraindicated should wait at least 28 days after the mRNA vaccine dose to receive the Janssen COVID-19 Vaccine.
Learn more about COVID-19 vaccine contraindications and precautions.
Precautions to Moderna COVID-19 Vaccine include:
- History of an immediate allergic reaction to any other vaccine or injectable therapy (i.e., intramuscular, intravenous, or subcutaneous vaccines or therapies)
- Contraindication to Janssen COVID-19 Vaccine
- Moderate or severe acute illness
The following considerations can be used to help the provider conduct a risk assessment for vaccination of patients with a precaution to vaccination:
- Risk of exposure to SARS-CoV-2
- Risk of severe disease or death due to COVID-19
- Unknown risk of anaphylaxis (including fatal anaphylaxis) following COVID-19 vaccination in a person with a history of an immediate allergic reaction to other vaccines or injectable therapies
- Ability of the patient to be vaccinated in a setting where appropriate medical care is immediately available for anaphylaxis. For people with a contraindication to another type of COVID-19 vaccine (i.e., Janssen viral vector vaccine), vaccination with another type (i.e., mRNA vaccines) should only be done in an appropriate setting under the supervision of a healthcare provider experienced in the management of severe allergic reactions.
Learn more about COVID-19 vaccine contraindications and precautions.
PEG can be found in:
- Osmotic laxatives and oral bowel preparations for colonoscopy procedures
- Many medications as an inactive ingredient or excipient (e.g., certain injectable contraceptives, steroids)
- Some therapeutic medications (e.g., some chemotherapeutics)
Additionally, cross-reactive hypersensitivity can occur between PEG and polysorbates.
Screen patients for contraindications and precautions prior to vaccination. If a patient identifies a history of allergic reaction to a medication with which you are unfamiliar, you may consider using the following resources to determine if a specific medication contains PEG, a PEG derivative, or polysorbates:
- FDA package insert for the specific medication
- National Institutes of Health DailyMed databaseexternal icon
- CDC’s vaccine excipient summarypdf icon
Yes. A side effect is not a contraindication to a second dose of mRNA COVID-19 vaccine. Common side effects to vaccination may include:
- Injection site pain, redness, or swelling
- Muscle pain
For most people, side effects last no longer than 1–2 days. Encourage patients to enroll in v-safe to tell CDC about any side effects after getting a COVID-19 vaccine and to receive reminders for a second dose.
People with an immediate allergic reaction to the first dose of an mRNA COVID-19 vaccine should not receive additional doses of either of the mRNA COVID-19 vaccines. An immediate allergic reaction to a vaccine or medication is defined as any hypersensitivity-related signs or symptoms consistent with urticaria, angioedema, respiratory distress (e.g., wheezing, stridor), or anaphylaxis that occur within 4 hours following administration. Attempt to determine whether reactions reported following vaccination are consistent with immediate allergic reactions versus other types of reactions commonly observed following vaccination, such as a vasovagal reaction or post-vaccination side effects (which are not contraindications to receiving the second vaccine dose).
People with a contraindication to mRNA COVID-19 vaccines may be able to receive Janssen COVID-19 Vaccine at least 28 days after the mRNA vaccine, but it is considered a precaution. In these cases, consider consultation with an allergist-immunologist to help determine if the patient can safely receive vaccination. Healthcare providers and health departments may also request a consultation from the Clinical Immunization Safety Assessment COVIDvax Project. Vaccination of these people should only be done in an appropriate setting under the supervision of a healthcare provider experienced in the management of severe allergic reactions.
See more information on:
There are two options for storing Moderna COVID-19 Vaccine. It may be stored in:
- Freezer between -50°C and -15°C (-58°F and 5°F) up to the expiration or beyond-use date (BUD). Keep vaccine vials in their box, and place in the storage unit.
- Refrigerator between 2°C and 8°C (36°F and 46°F) for up to 30 days prior to its first use. Do not refreeze.
Refer to the Moderna COVID-19 Vaccine product information or Moderna COVID-19 Vaccine Storage and Handling Summarypdf icon for more detailed information on storage.
Yes. You should immediately examine shipments for signs of damage and to guarantee receipt of the appropriate vaccine types and quantities.
- Examine the shipping container and vaccines for signs of physical damage.
- Check the contents against the packing list to be sure they match.
- Immediately check vaccine expiration dates to ensure you have not received any expired or soon-to-expire products.
- Immediately check the cold chain monitor (CCM), a device used to monitor vaccine temperatures during transport (if one was included), for any indication of a temperature excursion during transit.
Yes. Before puncturing the vial stopper, vaccine may be stored in the refrigerator between 2°C and 8°C (36°F and 46°F) for up to 30 days. After 30 days, contact the manufacturer for guidance before discarding any vials.
After the first dose has been withdrawn, the vial should be held between 2°C and 25°C (36°F and 77°F). Discard after 12 hours. Do not refreeze.
CDC requires vaccination providers participating in the COVID-19 Vaccination Program to use a specific type of TMD called a “digital data logger” (DDL) to monitor temperatures. A DDL provides the most accurate storage unit temperature information, including details on how long a unit has been operating outside the recommended temperature range (referred to as a “temperature excursion”). DDLs using a buffered temperature probe provide the most accurate way to measure actual vaccine temperatures. Always use DDLs with a current and valid Certificate of Calibration Testing.
For more storage and handling information, see:
No. After the first dose has been withdrawn, vials must be stored between 2°C and 25°C (46°F and 77°F) and used within 12 hours.
If the vaccine experienced problems during shipment (for example, damage or temperature excursion), contact
McKesson Specialty Customer Service at (833) 343-2703, Monday–Friday, 8 AM–8 PM Eastern Time.
If the vaccine experienced problems after it was received and placed into storage, contact the vaccine manufacturer for guidance on improper storage and handling. For temperature excursions affecting Moderna COVID-19 Vaccine, see Moderna’s temperature excursion toolexternal icon.
For temperature excursions (out-of-range temperatures), take immediate action:
- Label the vaccine “Do Not Use” and store at the recommended temperature range until you receive manufacturer guidance.
- Document the date and length of time of the excursion, storage unit temperature, room temperature, and inventory affected.
- Record any other relevant information.
- Contact the manufacturer for guidance on whether to use affected vaccines and whether patients need to be called for revaccination.
- Document the event and action taken for record-keeping requirements.
CDC recommends transporting vaccine in vials. However, there may be instances when the only option is to transport predrawn vaccine in a syringe. U.S. Pharmacopeia includes guidance for transporting predrawn vaccine in syringes in the USP COVID-19 Vaccine Toolkit: Operational Considerations for Healthcare Practitionersexternal icon.
Unpunctured vials can be transported for up to 12 hours. This time is cumulative, including the amount of transport time to and from clinics. All transport time is also included in the 30-day time frame. For example, if your transport time to and from a clinic is a total of 2 hours, any unpunctured vials have 10 hours of transport time left. If there is a clinic the following day, you may transport the vaccine again for up to 10 hours. Use Moderna COVID-19 Vaccine beyond-use date/time (BUD) tracking labelspdf icon to track and record transport time. This only applies to unpunctured vials. Punctured vials must be discarded if not used within 12 hours.
CDC recommends healthcare providers follow the dosing guidance from the manufacturer as outlined in the Emergency Use Authorization (EUA)external icon. CDC will update its guidance if the EUA and ancillary supply kits support obtaining additional doses per vial in the future.
No. While it is important to try to use every dose of vaccine possible, that should not be at the expense of missing an opportunity to vaccinate every eligible person when they are ready to get vaccinated. Strategies to ensure providers do not miss an opportunity to vaccinate every eligible person and limit wastage can be found online: Identification, Disposal, and Reporting of COVID-19 Vaccine Wastagepdf icon.
Contact the manufacturer. mRNA vaccine is very fragile and should not be shaken. Vials should only be gently swirled while held upright.
For all vaccine administration errors, inform the recipient of the vaccine administration error. Consult with the state immunization program or immunization information system (IIS) to determine how the dose should be entered into the IIS, both as an administered dose and to account for inventory.
Additionally, adverse events that occur after receipt of any COVID-19 vaccine should be reported to VAERS. Information on how to submit a report to VAERS is available at https://vaers.hhs.govexternal icon or 1-800-822-7967. Healthcare providers are required to report:
- Any vaccine administration error, even those not associated with an adverse event. Such errors include but are not limited to:
- Administering the vaccine subcutaneously instead of intramuscularly
- If administered subcutaneously, do not repeat the dose
- Administering the vaccine to a patient who is outside of the authorized age range
- If administered to a patient who is less than 12 years of age, do not give any additional dose at this time.
- If administered to a patient who is 12 through 17 years of age, you may administer Moderna COVID-19 Vaccine as the second dose. This is an off-label use, because Moderna COVID-19 Vaccine is not authorized in this age group.
- Administering the vaccine subcutaneously instead of intramuscularly
- Any serious adverse event
- Cases of multisystem inflammatory syndrome
- Any potential or diagnosed cases of myocarditis or pericarditis after vaccine receipt
- Cases of COVID-19 that result in hospitalization or death following COVID-19 vaccination under an EUA
Determine how the error occurred and implement strategiespdf icon to prevent it from happening again. A discussion on strategies to prevent errors can be found in the “Vaccine Administration” chapter of Epidemiology and Prevention of Vaccine-Preventable Diseases (Pink Book). Additional resources can be found on CDC’s vaccine administration web page, including a job aid for preventing errors.
Please note that interim recommendations for COVID-19 vaccine administration errors differ from ACIP’s general best practice guidelines. Review vaccine administration errors and deviations for COVID-19 vaccines to learn about the interim recommendation for each type of error.
If a lower-than-authorized dose volume is administered for any of the currently authorized vaccines, adhere to the following interim recommendation:
- If more than half of the dose was administered, do not repeat the dose. If the dose given in error is the first dose, administer the second dose at the recommended interval of 28 days. If this dose is the second dose, the series is complete, and no additional doses are needed.
- If less than half of the dose was administered or the proportion of the dose cannot be estimated, administer the authorized dose immediately in the opposite arm. If the dose given in error is the first dose, administer the second dose at the recommended interval of 28 days from the date of receipt of the valid dose (not the date of receipt of the erroneous dose).
Before vaccination, counsel patients about expected local and systemic side effects.
Common side effects include:
- Muscle pain
Clinical trial data demonstrated vaccine efficacy was 94.1% against symptomatic, laboratory-confirmed COVID-19 following receipt of 2 doses of Moderna COVID-19 Vaccine.
Both doses are necessary for developing the most protection; effectiveness of a single dose has not been systematically evaluated.