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What is COVID-19 vaccine?

Updated October 06, 2023


There are two COVID-19 vaccines licensed and recommended in the U.S. by the U.S. Food and Drug Administration (FDA) and the U.S. Centers for Disease Control and Prevention (CDC). Comirnaty,  an mRNA vaccine developed and produced by Pfizer- BioNTech and SPIKEVAX,  an mRNA vaccine developed and manufactured by Moderna with the National Institutes of Allergy and Infectious Disease (NIAID). Both vaccines are approved for use in persons 12 years of age and older.

Messenger RNA (mRNA) vaccines are gene based vaccines that involve injecting lipid nanoparticles containing mRNA (genetic code) that enable the vaccine to get past the cell wall, into the intracellular space, then causes the cell’s ribosome to make viral proteins (antigen that stimulate the immune system.)  In essence, an mRNA vaccine tricks the body into producing the viral proteins to trigger an immune response.  Messenger RNA vaccines can be produced in the lab using faster and less expensive processes than traditional vaccines. 

Additional COVID-19 Vaccines are available for use through Emergency Use Authorization (EUA) by the FDA. These vaccines include two mRNA COVID-19 vaccines produced by Pfizer-BioNTech for use in infants and children aged 6 months through 4 years and for children five through 11 years of age  and one mRNA COVID-19 vaccine produced by Moderna for use in infants aged 6 months through 11 years.  There is one protein subunit vaccine, Novavax, authorized for use in individuals 12 years of age and older. 

According to the FDA, vaccine makers may submit an application to have their products approved under an Emergency Use Authorization (EUA). Under EUA authority, the FDA Commissioner may permit “unapproved medical products or unapproved uses of approved medical products to be used in an emergency to diagnose, treat, or prevent serious or life-threatening diseases or conditions caused by CBRN (CBRN = chemical, biological, radiological, nuclear) threat agents when there are no adequate, approved, and available alternatives.”9 To learn more about EUA products and vaccines and consumer rights, visit NVIC’s FAQ on  Emergency Use Vaccines (EUA) & Vaccine Injury Compensation.

In September 2023, the FDA approved an updated mRNA COVID-19 vaccine developed and manufactured by Pfizer-BioNTech for use in persons 12 years and older to target the Omicron variant XBB.1.5. 

Comirnaty COVID-19 mRNA Vaccine was initially authorized for use under EUA as Pfizer-BioNTech COVID-19 vaccine in persons 16 years and older by the in December 2020. This vaccine targeted the original SARS-CoV-2 virus and was authorized to be given as a 2-dose series.  In August 2021 the FDA licensed and granted EUA status to Comirnaty COVID-19 vaccine, an mRNA vaccine developed by BioNTech, for use in persons 16 years of age and older.  The FDA licensed Comirnaty for use in teens 12 through 15 years in July 2022.  In August 2022, the FDA authorized use of a bivalent Pfizer-BioNTech COVID-19 vaccine containing the original SARS-CoV2 strain and the Omicron BA.4/BA.5 variant. 

According to the Comirnaty COVID-19 vaccine package insert “The modRNA in the Pfizer-BioNTech COVID-19 Vaccine is formulated in lipid particles, which enable delivery of the RNA into host cells to allow expression of the SARS-CoV-2 S antigen. The vaccine elicits an immune response to the S antigen, which protects against COVID-19.”  

Each 0.3mL dose contains 30 mcg of a nucleoside-modified messenger RNA (modRNA) that encodes the viral spike (S) glycoprotein of SARS-CoV-2 Omicron Variant lineage XBB.1.5.

Additional vaccine ingredients include lipids (0.43 mg ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 0.05 mg 2-(polyethylene glycol 2000)-N,N-ditetradecylacetamide, 0.09 mg 1,2-distearoyl-sn-glycero-3-phosphocholine, and 0.2 mg cholesterol, 0.01 mg monobasic potassium phosphate, 0.36 mg sodium chloride, 0.07 mg dibasic sodium phosphate dihydrate, 0.01 mg potassium chloride, and 6 mg sucrose. The 0.9 percent sodium chloride Injection diluent adds another 2.16 mg sodium chloride per dose. The vaccine does not contain a preservative and the vaccine vial stoppers are free of latex. 

The 2023-2024 Comirnaty COVID-19 vaccine is approved to be given intramuscularly (IM) as a single dose, at least two months after receipt of a previous COVID-19 vaccine dose. 

There is no data available on the co-administration of the Comirnaty COVID-19 Vaccine with any other vaccine product.  

Comirnaty COVID-19 vaccine may not offer protection to all individuals.   This vaccine is also incapable of reducing or stopping transmission of the virus. This means that vaccinated individuals may still be capable of transmitting the virus to others.   

Individuals with immunocompromising conditions, including those who take medications that induce immunosuppression may have a decreased immune response to Comirnaty COVID-19 vaccine.  

According the Comirnaty package insert, data on the safety and effectiveness of the vaccine for use in pregnant women is not known. It is also not known whether the vaccine can be transmitted through breastmilk.  

Comirnaty COVID-19 vaccine has not been studied for its potential to cause cancer, genotoxicity or male infertility. 

On September 12, 2023, the CDC’s ACIP voted to approve use of the 10mcg dose of the 2023-2024 Comirnaty COVID-19 mRNA vaccine targeting the Omicron variant XBB.1.5 in all persons aged 12 years and older. 

In September 2023, the FDA issued an EUA for an updated Pfizer-BioNTech COVID-19 mRNA vaccine for use in children aged five through 11 years of age to target the Omicron variant XBB.1.5. 

The FDA initially authorized use of a 10-mcg dose of Pfizer-BioNTech mRNA COVID-19 vaccine to target the original SARS-CoV-2 strain for children 5 through 11 years of age in October 2021,  and an updated vaccine product containing the original SARS-CoV-2 variant and the Omicron BA.4/BA.5 variant in October 2022.  These previously authorized vaccine formulations are no longer available for use in the U.S. 

According to the Fact Sheet provided by the FDA, for 2023-2024, each 0.3 ml dose of Pfizer-BioNTech COVID-19 Vaccine contains 10mcg of nucleoside modified messenger RNA (mRNA) that encodes the pre-fusion stabilized Spike glycoprotein (S) of SARS-CoV-2 virus targeting the Omicron variant XBB.1.5. 

Each dose also contains a total lipid content of (0.14 mg (4- hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 0.03 mg 1,2-distearoyl-sn-glycero-3-phosphocholine, and 0.06 mg cholesterol), 0.02 mg 2[(polyethylene glycol)-2000- N,N-ditetradecylacetamide, 31 mg sucrose, 0.06 mg tromethamine, and 0.4 mg tromethamine hydrochloride. The vaccine also contains 0.9mg sodium chloride per dose. The vaccine vial stoppers are free of latex and the vaccine does not contain a preservative. 

The vaccine is recommended to be administered intramuscularly (IM). There is no data on the safety or effectiveness of administering the Pfizer-BioNTech COVID-19 vaccine with any other vaccine. 

Pfizer-BioNTech COVID-19 vaccine has not been studied for its potential to cause cancer, genotoxicity or male infertility. 

On September 12, 2023, the CDC’s ACIP voted to approve use of the 10mcg dose of the Pfizer-BioNTech 2023-2024 COVID-19 mRNA vaccine targeting the Omicron variant XBB.1.5 in all children 5 through 11 years of age. 

In September 2023, the FDA granted an EUA for an updated Pfizer-BioNTech mRNA COVID-19 vaccine for use in children aged 6 months through 4 years of age to target the Omicron variant XBB.1.5. 

The FDA originally issued an EUA for a 3mcg dose of Pfizer-BioNTech mRNA COVID-19 vaccine containing the original SARS-CoV-2 strain for infants and young children aged 6 months through 4 years of age in June 2022,  and a bivalent booster dose containing the original SARS-CoV-2 and Omicron strains BA.4/BA.5 in December 2022.  These previously authorized vaccine formulations are no longer available for use in the U.S. 

According to the Fact Sheet provided by the FDA, each 0.3 mL dose of the vaccine contains 3mcg of nucleoside modified messenger RNA (mRNA) that encodes the pre-fusion stabilized Spike glycoprotein (S) of SARS-CoV-2 virus.  

Each dose also contains the following ingredients: 9.4 mg sucrose, 0.02 mg tromethamine, 0.12 mg tromethamine hydrochloride; lipids (0.04 mg ((4- hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 0.005 mg 2[(polyethylene glycol)-2000- N,N-ditetradecylacetamide, 0.01 mg 1,2-distearoyl-sn-glycero-3-phosphocholine, and 0.02 mg cholesterol). The sterile 0.9 percent sodium chloride diluent adds 1.88 mg of sodium chloride per dose. The vaccine vial stoppers are free of latex and the vaccine does not contain a preservative. 

Children aged six months through four years are recommended to receive at least 3-doses of Pfizer-BioNTech mRNA COVID-19 vaccine. The number of recommended doses of the authorized 3mcg Pfizer-BioNTech COVID-19 vaccine targeting Omicron variant XBB.1.5 will depend on previously authorized doses of COVID-19 vaccine. 

Pfizer-BioNTech COVID-19 vaccine has not been studied for its potential to cause cancer, genotoxicity or male infertility. 

The CDC’s ACIP voted to approve use of the 3mcg dose of the Pfizer-BioNTech 2023-2024 mRNA COVID-19 vaccine targeting the Omicron variant XBB.1.5 for use in all children aged 6 months through 4 years of age on September 12, 2023. 

On September 11, 2023, the FDA approved an updated mRNA COVID-19 vaccine developed and manufactured by Moderna for use in persons 12 years and older to target the Omicron variant XBB.1.5. 

The Moderna mRNA COVID-19 vaccine containing the original SARS-CoV-2 virus was initially issued an EUA by the FDA in December 2020 for use in persons 18 years of age.  On January 31, 2022, the FDA licensed and granted EUA status to Moderna for SPIKEVAX COVID-19 vaccine for use in persons 18 years of age and older. The FDA also stated that use of SPIKEVAX and the experimental Moderna mRNA COVID-19 vaccine were interchangeable due to having the same formulation.  In August 2022, the FDA authorized use under EUA to Moderna for a bivalent COVID-19 vaccine containing the original SARS-CoV-2 virus and the Omicron BA.4/BA.4 variant in persons 18 years and older.  A bivalent COVID-19 vaccine was also authorized for use in adolescents aged 12 through 17 years in October 2022.  These previously authorized vaccine formulations are no longer available for use in the U.S. 

According to the SPIKEVAX COVID-19 vaccine package insert “The nucleoside-modified mRNA in the Moderna COVID-19 Vaccine is formulated in lipid particles, which enable delivery of the nucleoside-modified mRNA into host cells to allow expression of the SARS-CoV-2 S antigen. The vaccine elicits an immune response to the S antigen, which protects against COVID-19.” 

Each 0.5 ml dose of SPIKEVAX 2023-2024 mRNA COVID-19 vaccine contains 50 mcg of nucleoside modified messenger RNA (mRNA) that encodes the pre-fusion stabilized Spike glycoprotein (S) of SARS-CoV-2 Omicron variant lineage Omicron XBB.1.5. 

Each dose also contains a total lipid content of 1.01 mg (SM-102, polyethylene glycol [PEG 2000 dimyristoyl glycerol [DMG, cholesterol, and 1,2-distearoyl-sn-glycero-3-phosphocholine [DSPC), 0.25 mg tromethamine, 0.021 mg acetic acid, 1.2 mg tromethamine hydrochloride, 43.5 mg sucrose and 0.10 mg sodium acetate trihydrate. The vaccine does not contain a preservative and the vaccine vial stoppers are free of latex.  

The 2023-2024 SPIKEVAX COVID-19 vaccine is approved to be given intramuscularly (IM) as a single dose, at least two months after receipt of a previous COVID-19 vaccine dose. 

The duration of vaccine-acquired immunity from SPIKEVAX COVID-19 vaccine is not known. The vaccine offers only minimal protection against infection and transmission. This means that vaccinated individuals can still become infected with the virus and spread it on to others. 

There is no data available on the co-administration of the SPIKEVAX COVID-19 Vaccine with any other vaccine product.  

Individuals with immunocompromising conditions, including those who take medications that induce immunosuppression may have a decreased immune response to SPIKEVAX COVID-19 vaccine. 

According the SPIKEVAX package insert, data on the safety and effectiveness of the vaccine for use in pregnant women is not known. It is also not known whether the vaccine can be transmitted through breastmilk. 

SPIKEVAX COVID-19 vaccine has not been studied for its potential to cause cancer, genotoxicity or male infertility. 

On September 12, 2023, the CDC’s ACIP voted to approve use of the 50mcg dose of the 2023-2024 SPIKEVAX COVID-19 mRNA vaccine targeting the Omicron variant XBB.1.5 in all persons aged 12 years and older. 

In September 2023, the FDA issued an EUA for an updated Moderna COVID-19 mRNA vaccine for use in children aged 6 months through 11 years of age to target the Omicron variant XBB.1.5. 

The FDA originally issued an EUA to Moderna in June 2022 for an mRNA COVID-19 vaccine containing the original SARS-CoV-2 virus for use in children ages 6 months through 11 years of age.  In October 2022, the FDA authorized use of a Moderna bivalent COVID-19 vaccine containing the original SARS-CoV-2 variant and the Omicron BA.4/BA.5 variant in children 6 through 11 years  and in infants and children aged 6 months through five years in December 2022.  These previously authorized vaccine formulations are no longer available for use in the U.S. 

According to the Fact Sheet provided by the FDA, each 0.25mL dose of Moderna COVID-19 mRNA vaccine contains 25 mcg of nucleoside-modified messenger RNA (mRNA) encoding the pre-fusion stabilized Spike glycoprotein (S) of SARS-CoV-2 Omicron variant lineage XBB.1.5. 

Additional ingredients contained in the vaccine include 21.8 mg sucrose, 0.13 mg tromethamine, 0.62 mg tromethamine hydrochloride, 0.011 mg acetic acid, 0.049 mg sodium acetate trihydrate, and a total lipid content of 0.5 mg (SM-102, polyethylene glycol [PEG 2000 dimyristoyl glycerol [DMG, cholesterol, and 1,2-distearoyl-sn-glycero-3-phosphocholine [DSPC). The vaccine does not contain a preservative and the vaccine vial stopper does not contain natural latex rubber. 

Children aged six months through four years are recommended to receive at least 2 doses of Moderna mRNA COVID-19 vaccine. The number of recommended doses of the authorized 25mcg Moderna COVID-19 vaccine targeting Omicron variant XBB.1.5 will depend on previously authorized doses of COVID-19 vaccine. Children aged five through 11 years are recommended to receive one dose of the 2023-2024 Moderna COVID-19 vaccine, at least two months after receipt of a previous COVID-19 dose.  

There is no data on the safety or effectiveness of administering the Moderna COVID-19 vaccine with any other vaccine. 

Moderna COVID-19 vaccine has not been studied for its potential to cause cancer, genotoxicity or male infertility. 

On September 12, 2023, the CDC’s ACIP voted to approve use of the 25mcg dose of the 2023-2024 Moderna COVID-19 mRNA vaccine targeting the Omicron variant XBB.1.5 in all children aged 6 months through 11 years. 

In October 2023, the FDA issued an EUA to Novavax for its adjuvanted COVID-19 vaccine containing spike protein from the Omicron XBB.1.5 variant of SARS-CoV-2. 

The FDA initially issued an EUA to Novavax for an adjuvanted COVID-19 vaccine, for use in adults 18 years and older who had not received a prior dose of COVID-19 vaccine on July 13, 2022. The vaccine was authorized as a two-dose primary series, to be administered intramuscularly three weeks apart.  The EUA was expanded on August 19, 2022 to include adolescents aged 12 through 17 years.  The original Novavax COVID-19 vaccine is no longer authorized for use in the U.S. 

Maryland-based Novavax Inc, a biotechnology company which had never successfully delivered a product to market,  developed an experimental vaccine using recombinant nanoparticle technology. Referred to as a protein subunit vaccine,  NVX‑CoV2373 contains Novavax’s patented saponin-based Matrix-M™ adjuvant designed to enhance the immune response and stimulate high levels of neutralizing antibodies. 

Matrix-M1 contains nm (nanometers) of nanoparticles composed of Quillaja saponins, phospholipid and cholesterol. Quillaja saponins are chemical compounds extracted from the soapbox tree and are used as emulsifiers in food additives and beverages. 

According to the fact sheet for health care providers administering Novavax COVID-19 vaccine, each 0.5 mL dose of the Adjuvanted Novavax COVID-19 Vaccine contains 5 mcg of SARS-CoV-2 recombinant spike protein from the SARS-CoV-2 Omicron variant XBB.1.5 and 50 mcg Matrix-M adjuvant. The Matrix-M adjuvant is made of Fraction-A (42.5 mcg) and Fraction-C (7.5 mcg) of saponin extracts from the soapbark tree (Quillaja saponaria Molina). The recombinant spike protein is made by recombinant DNA technology in an insect cell line that is derived from cells of the Spodoptera frugiperda species. 

Each 0.5mL dose of the Adjuvanted Novavax COVID-19 vaccine also contains the following ingredients: potassium dihydrogen phosphate (3.85 mcg), potassium chloride (2.25 mcg), disodium hydrogen phosphate dihydrate (14.7 mcg), disodium hydrogen phosphate heptahydrate (2.465 mg), cholesterol, phosphatidylcholine, sodium dihydrogen phosphate monohydrate (0.445 mg), sodium chloride (8.766 mg) and polysorbate 80 (0.050 mg), and Water for Injection. The pH is adjusted with either sodium hydroxide or hydrochloric acid. Each 0.5 mL dose of the Novavax vaccine may also contain residual amounts of baculovirus and Sf9 cell proteins (≤ 0.96 mcg), lentil lectin (< 0.025 mcg), methyl-α-D-mannopyranoside (2 mcg), baculovirus and cellular DNA (≤ 0.00016 mcg), Triton X-100 (< 0.025 mcg), simethicone (< 0.92 mcg), pluronic F-68 (< 2.19 mcg), and Tergitol (NP9) (< 0.05 mcg). The Adjuvanted Novavax COVID-19 vaccine does not contain preservative and the vial stoppers are not made with natural rubber latex.  

The Adjuvanted Novavax COVID-19 vaccine is authorized to be given as a single dose to individuals 12 years of age and older who have previously received a dose of COVID-19 vaccine. Individuals who have not received any COVID-19 vaccines are recommended to receive two doses of adjuvanted Novavax COVID-19 vaccine at least three weeks apart. 

IMPORTANT NOTE: NVIC encourages you to become fully informed about COVID-19 and the COVID-19 vaccine by reading all sections in the table of contents, which contains many links and resources such as the manufacturer product information inserts, and to speak with one or more trusted health care professionals before making a vaccination decision for yourself or your child. This information is for educational purposes only and is not intended as medical advice.


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