COVID-19 Vaccine FAQs for Healthcare Professionals

Below are answers to commonly asked clinical questions that apply to all authorized COVID-19 vaccines.

For clinical questions on the following specific COVID-19 vaccines, see:

About Vaccines

All staff supporting COVID-19 vaccination efforts should receive ongoing training as new COVID-19 vaccines become available and recommendations evolve. Review and complete training and core competencies by professional qualification. Additionally, for healthcare professionals new to vaccination, the COVID-19 Vaccination Training Programs and Reference Materials for Healthcare Professionals provide a comprehensive list of suggested training and reference materials.

For more immunization training resources, see Resources for Health Care Providers and Immunization Education and Training.

Vaccination Schedule and Use

COVID-19 vaccines are not interchangeable. The safety and effectiveness of a mixed-product series have not been evaluated. Every effort should be made to determine which vaccine product was administered as the first dose to ensure completion of 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 two different mRNA COVID-19 vaccine products are administered, no additional doses of either product are recommended at this time.
  • 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.

Implement 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.

No. You may administer COVID-19 vaccine and other vaccines without regard to timing. This includes simultaneous administration of COVID-19 vaccine and other vaccines on the same day, as well as coadministration within 14 days. It is unknown whether reactogenicity of 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 another vaccine(s) with 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.

A patient is considered fully vaccinated ≥2 weeks after a 2-dose mRNA COVID-19 vaccine series or ≥2 weeks after a single dose of Janssen COVID-19 Vaccine. The need for and timing of COVID-19 booster doses have not been established. No additional doses are recommended at this time.

Vaccine Indications

Yes, you may administer any currently authorized 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
  • 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.

People with a history of an episode of immune-mediated syndrome characterized by thrombosis and thrombocytopenia (e.g., heparin-induced thrombocytopenia) should be offered Moderna COVID-19 Vaccine or Pfizer-BioNTech COVID-19 Vaccine if it has been 90 days or less since their illness resolved. After 90 days, patients may be vaccinated with any FDA-authorized COVID-19 vaccine.

More information is available at: Clinical Care Considerations for COVID-19 Vaccination

Immunocompromised patients can receive any currently authorized COVID-19 vaccine; however, you should consider counseling them and timing immunosuppressive therapies.

Counsel immunocompromised patients about the:

  • Unknown vaccine safety profile and effectiveness in immunocompromised populations
  • Potential for reduced immune responses
  • Need to continue to follow current guidance to protect themselves against COVID-19

Data are currently insufficient to inform optimal timing of COVID-19 vaccination and receipt of immunosuppressive therapies. However, based on general best practices for vaccination of immunocompromised people, ideally COVID-19 vaccination should be completed at least 2 weeks before initiation of immunosuppressive therapies. When it is not possible to administer a complete COVID-19 vaccine series (i.e., 2 doses of an mRNA vaccine or a single dose of Janssen COVID-19 Vaccine) in advance, you may still vaccinate patients receiving immunosuppressive therapy. Decisions to delay immunosuppressive therapy to complete COVID-19 vaccination should consider the patient’s risks related to their underlying condition.

At this time, revaccination is not recommended after patients regain immune competence. Recommendations on revaccination or additional doses of COVID-19 vaccines may be updated when more information is available.

Learn more about vaccinating patients with underlying medical conditions.

Yes. Pregnant or lactating people are eligible for and can receive any of the currently authorized COVID-19 vaccines; ACIP does not state a product preference.

However, you should talk to pregnant, lactating, 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 COVID-19 vaccines (i.e., mRNA vaccines)

When making a decision about vaccination, you and your pregnant patient should consider the:

  • Level of COVID-19 community transmission
  • Patient’s personal risk of contracting COVID-19
  • Risks of COVID-19 to the patient and potential risks to the fetus
  • Known and potential benefits of vaccination
  • Vaccine effectiveness
  • Vaccine side effects
  • Limited but growing evidence about the safety of COVID-19 vaccination during pregnancy

Encourage pregnant people who choose to be 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 lactating people and considerations for use of the Janssen COVID-19 Vaccine in certain populations.

Recommendations for vaccination depend on when a person has or had SARS-CoV-2 infection and when they received treatment.

People with a history of 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 children (MIS-C) or 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-C or 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.

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. 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.

As with other vaccines, a moderate or severe illness is a precaution to receiving any currently authorized 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 of reinfection is low in the months after initial infection, people with a precaution to vaccination and recent COVID-19 may choose to delay vaccination.

Vaccine Storage and Handling

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.

Note that not all DDLs can measure ultra-cold temperatures. For accurate ultra-cold temperature monitoring, it is essential to use an air-probe or a probe designed specifically for ultra-cold temperatures with the DDL.

For the Pfizer-BioNTech COVID-19 vaccine, there are additional considerations for using a TMD with the thermal shipping container. Refer to the Pfizer-BioNTech COVID-19 Vaccine Storage and Handling Summary and Pfizer-BioNTech COVID-19 Vaccine web page for more information.

If the vaccine experienced problems during shipment (for example, damage or temperature excursion), contact:

  • Directly distributed vaccine (Pfizer): Contact Pfizer at 800-666-7248 (option 8) or CVGovernment@Pfizer.com.
  • Centrally distributed vaccine (for example, Moderna): 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 (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 recalled for revaccination.
  • Document the event and action taken for record-keeping requirements.

Vaccine Administration

Intramuscular injection is the recommended route for all COVID-19 vaccines.

The recommended site to administer an intramuscular injection to adolescents and adults is the deltoid muscle. When coadministering vaccines, more than one vaccine may be injected into the deltoid muscle. Separate injection sites by 1 inch. If administering COVID-19 vaccine with vaccines that tend to be locally reactogenic (e.g., tetanus-toxoid–containing vaccines, vaccines with adjuvants), administer vaccine in separate limbs, if feasible. You may use the vastus lateralis muscle of the anterolateral thigh as an alternate site. Refer to the following job aids for identifying administration sites:

No. CDC recommends following these practices:

  • Never combine or “pool” partial doses from two or more vials to obtain a full dose of vaccine.
  • Withdraw only the number of doses authorizedexternal icon for the specific vaccine.
  • Discard the vaccine vial and remaining vaccine if the amount of vaccine left in the vial is not a full dose.

Although no one wants to waste vaccine, it is crucial for infection control and patient safety to administer vaccine properly. Combining vaccine doses from multiple vials can result in cross-contamination, potentially causing bacterial infection in patients.

The deltoid muscle of the arm is the preferred site for intramuscular injection. If the deltoid muscle cannot be used or accessed, the vastus lateralis muscle of the anterolateral thigh can be used.

The Z-track injection technique is more commonly used for irritating medication (e.g., iron preparation). It is not recommended for vaccine administration. CDC recommends expelling the air when drawing vaccine from a vial into a regular syringe because the amount of air drawn into the syringe may be larger than the amount in a manufacturer-filled syringe. Expelling the air is part of general medication guidelines for drawing medication into a syringe. To avoid loss of vaccine, leave the needle in the vial while expelling air.

Needle gauge and length recommendations vary for adolescents based on age, and for adults based on age, gender, and weight. Use CDC’s Vaccine Administration: Needle Gauge and Length job aid to help you determine the appropriate gauge and length. A discussion of vaccine administration best practices can be found in the “Vaccine Administration” chapter of Epidemiology and Prevention of Vaccine-Preventable Diseases (Pink Book).

COVID-19 vaccines are administered by intramuscular injection. For all intramuscular injections, the needle should be long enough to reach the muscle mass and prevent vaccine from seeping into subcutaneous tissue. Ensuring the vaccine is given in the muscle is important to optimize immunogenicity and minimize adverse reactions at the injection site. If vaccine is given subcutaneously with the incorrect needle length, patients may experience more pain, irritation, and redness at the injection site.

Needle gauge and length recommendations vary for adolescents based on age, and for adults based on age, gender, and weight. CDC’s needle gauge and length chart, included in the ancillary kits, outlines ACIP’s recommendations for needle length. Other vaccine administration and injection resources can be found in CDC’s Vaccine Administration Resource Library.

No. You should not aspirate before giving any vaccine, including COVID-19 vaccines. Aspiration can increase pain because of the combined effects of a longer needle-dwelling time in the tissues and shearing action (wiggling) of the needle. A discussion of vaccine administration best practices can be found in the “Vaccine Administration” chapter of Epidemiology and Prevention of Vaccine-Preventable Diseases (Pink Book).

No. These devices or a needle should not be left inserted into a medication vial septum for multiple uses. This provides a direct route for microorganisms to enter the vial and contaminate the fluid in these devices.

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.

For all vaccine administration errors:

To reduce the risk of fake or counterfeit vaccines, dispose of vials and packaging as medical waste by placing vials in a sharps container and packaging in a red medical waste bag. If medical waste containers are in short supply, deface or safely crush packaging materials so they cannot be reintroduced or reproduced. After the products are sufficiently defaced or destroyed, dispose with regular waste.

The disposal process for unused COVID-19 vaccine and diluent may be different. For guidance, contact your jurisdiction’s immunization program.

Vaccination Documentation

Vaccination providers enrolled in the COVID-19 Vaccination Program are required to:

  • Document vaccine administration in their medical record systems within 24 hours of administration.
  • Report administration data to the relevant system (i.e., IIS) for the jurisdiction as soon as practicable and no later than 72 hours after administration. See data reporting requirements.
  • Report inventory daily using Vaccines.gov. In some jurisdictions, providers may report vaccine inventory to the jurisdiction’s IIS for the jurisdiction to upload into Vaccines.gov. If you have questions about the process for your jurisdiction, please contact your jurisdiction’s immunization program.
  • Report the following to VAERSexternal icon:
    • Vaccine administration errors
    • Serious adverse events
    • Multisystem inflammatory syndrome
    • Cases of COVID-19 that result in hospitalization or death after the recipient has received COVID-19 vaccine

There are additional requirements for COVID-19 vaccination providers besides documentation (e.g., providing the Emergency Use Authorization (EUA) Fact Sheet for Recipients and Caregivers to vaccine recipients). Please refer to your COVID-19 vaccination provider agreement for all provider requirements.

Some people may have received a COVID-19 vaccine outside of the United States. Consider the following for these patients:

  • People who received an FDA-authorized COVID-19 vaccine and have received all the recommended doses do not need any additional doses. People who received the first dose of an FDA-authorized COVID-19 vaccine that requires two doses do not need to restart the vaccine series in the United States but should receive the second dose as close to the recommended time as possible.
  • People who have received all recommended doses of a COVID-19 vaccine listed for emergency use by the World Health Organization (WHO) do not need any additional doses with an FDA-authorized COVID-19 vaccine. See Interim Clinical Considerations for Use of COVID-19 Vaccines Currently Authorized in the United States for a list of WHO vaccines listed for emergency use.
  • People who have not received all the recommended doses of a COVID-19 vaccine listed for emergency use by WHO may be offered a complete FDA-authorized COVID-19 vaccine series. Wait at least 28 days after the last dose of the non-FDA-authorized vaccine before administering an FDA-authorized COVID-19 vaccine.

People who received all or some of the recommended doses of a COVID-19 vaccine not listed for emergency use by WHO and not authorized by FDA may be offered a complete FDA-authorized COVID-19 vaccine series. Wait at least 28 days after the last dose of the non-authorized vaccine before administering an FDA-authorized COVID-19 vaccine.

No. VISs are only available for certain licensed vaccines. Under an EUA, there is not a VIS for an authorized vaccine. Instead, providers are legally required to provide the FDA-authorized EUA Fact Sheet for Recipients and Caregivers to vaccine recipients or their guardians. The Fact Sheet for Recipients and Caregivers includes:

  • Basic information on COVID-19, symptoms, and what to discuss with a healthcare provider before vaccination
  • Who should and should not receive the vaccine
  • A statement that recipients have the choice to receive the vaccine
  • Vaccine series information
  • Potential and known risks and benefits of the vaccine, including common side effects
  • Information on reporting side effects to VAERS
  • An explanation of what an EUA is and why it is issued
  • Any approved available alternatives for preventing COVID-19
  • Additional resources

Although you are required to provide the vaccine-specific Fact Sheet for Recipients and Caregivers to vaccine recipients or their caregivers, you are not required to document that you did so. However, to help facilitate such documentation in electronic medical records/immunization information systems for vaccination providers who choose to do so, CDC is leveraging the existing vaccine information statement (VIS) Code Set infrastructure, barcoding, and URLs to provide the information needed for various systems. This is similar to the electronic system and workflow documentation of the VIS. The barcode at the bottom of the last page of the EUA Fact Sheet for Recipients and Caregivers may be scanned to capture in electronic medical records/immunization information systems that the fact sheet was provided to the vaccine recipient or caregiver.

Vaccine Safety and Efficacy

Adverse events that occur in a recipient following COVID-19 vaccination should be reported to the Vaccine Adverse Event Reporting System (VAERS)external icon. Vaccination providers are required by the FDA to report:

  • Vaccine administration errors
  • Serious adverse events
  • Cases of multisystem inflammatory syndrome
  • Cases of COVID-19 that result in hospitalization or death following COVID-19 vaccination under an EUA

Reporting is encouraged for any other clinically significant adverse event, even if it is uncertain whether the vaccine caused the event. Also, vaccine recipients can report adverse events that occur after vaccination. Information on how to submit a report to VAERS is available at https://vaers.hhs.govexternal icon or by calling 1-800-822-7967.

The VAERS reporting requirements for COVID-19 vaccines (under Emergency Use Authorization) are different from those for routine vaccines licensed in the United States. Healthcare providers are strongly encouraged to report vaccine administration errors involving any licensed vaccine. However, healthcare providers are required to report COVID-19 vaccine administration errors to VAERSexternal icon.

Before vaccination, counsel patients about expected local and systemic side effects.

Common side effects include:

Local reactions:

  • Pain
  • Redness
  • Swelling

Systemic reactions:

  • Tiredness
  • Headache
  • Muscle pain
  • Chills
  • Fever
  • Nausea

If receiving Janssen COVID-19 Vaccine, women younger than 50 years old should be made aware of the rare but increased risk of blood clots with low platelets following vaccination and the availability of other COVID-19 vaccines where this risk has not been observed. Provide recipients or caregivers (as applicable) the EUA Fact Sheet for Recipients and Caregiversexternal icon.

Recent studies show that the mRNA vaccines (Pfizer-BioNTech, Moderna) help keep people from spreading the virus that causes COVID-19, and studies are underway to learn more about the benefits of Johnson & Johnson’s Janssen vaccine. Guidance for fully vaccinated people is available and will continue to be updated as more information becomes available.

The potential for asymptomatic transmission of the virus that causes COVID-19 underscores the importance of applying infection prevention practices to encounters with all patients while in a healthcare facility. These include physical distancing, respiratory and hand hygiene, surface decontamination, and source control. Vaccination providers should refer to the guidance developed to prevent the spread of COVID-19 in healthcare settings, including outpatient and ambulatory care settings.

General practices for the safe delivery of vaccination services is available in the Interim Guidance for Routine and Influenza Immunization Services During the COVID-19 Pandemic.

People who have been fully vaccinated can resume activities they did prior to the pandemic without wearing a mask or physically distancing, except where required by federal, state, local, tribal, or territorial laws, rules, and regulations, including local business and workplace guidance. People are considered fully vaccinated

  • 2 weeks after their second dose in a 2-dose series, such as the Pfizer-BioNTech or Moderna vaccines, or
  • 2 weeks after a single-dose vaccine, such as Johnson & Johnson’s Janssen vaccine

If patients have been fully vaccinated

  1. They can resume activities that they did prior to the pandemic.
  2. They can resume activities without wearing a mask or staying 6 feet apart, except where required by federal, state, local, tribal, or territorial laws, rules, and regulations, including local business and workplace guidance (e.g., healthcare facilities, homeless shelters, correctional facilities).
  3. If they travel in the United States, they do not need to get tested before or after travel or self-quarantine after travel.
  4. They need to pay close attention to the situation at their international destination before traveling outside the United States.
  5. If they’ve been around someone who has COVID-19, they do not need to stay away from others or get tested unless they have symptoms.

However, they should continue to

You may need to further discuss activities with people who have a condition or are taking medications that weaken the immune system. They may need to keep taking precautions to prevent COVID-19.

For more information, visit CDC’s When You’ve Been Fully Vaccinated webpage.

Off-Site Clinics

CDC does not recommend predrawing vaccine. If vaccine must be predrawn:

  • Set up a separate administration station for each vaccine type to prevent medication errors.
  • Draw up vaccines only after arriving at the clinic site or mass vaccination event.
  • Each person administering vaccines should draw up no more than one multidose vial or 10 doses* at one time.
  • Monitor patient flow to avoid drawing up unnecessary doses.
  • Predraw reconstituted vaccine into a syringe only when ready for administration.
  • If predrawn vaccine is not used within 30 minutes of being reconstituted, follow manufacturer guidance for storage conditions and time limits.

*You may withdraw a total of 12 doses (2 multidose vials) of Pfizer-BioNTech COVID-19 Vaccine. This applies only to Pfizer-BioNTech COVID-19 Vaccine.

See CDC’s Vaccine Storage and Handling Toolkit for more information.

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.

Page last reviewed: June 2, 2021