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What do we know about the Moderna vaccine so far?

This article was published on
May 6, 2021

This explainer is more than 90 days old. Some of the information might be out of date or no longer relevant. Browse our homepage for up to date content or request information about a specific topic from our team of scientists.

Update on May 6, 2021: A pre-print study entered on May 5th, 2021 reported on early results from phase 2 research on Moderna's booster vaccines. The boosters are shots given to people who had received both doses of the Moderna vaccine (mRNA-1273) about six months earlier. One booster, mRNA-1273.351, aims to protect patients from the COVID-19 variant first identified in the Republic of South Africa (B.1.351). The other booster is a smaller dose (50 micrograms) of the existing mRNA-1273 vaccine.

Researchers analyzed blood from patients who received the boosters and it showed a good response in fighting against ("neutralizing") the variants B.1.351 (first identified in the Republic of South Africa) and P1 (first identified in Brazil).

The boosters have been reported to meet safety standards, with side effects similar to those reported in earlier mRNA vaccine studies. Side effects were generally mild and included pain at the injection site, fatigue, headache, muscle pain, and joint pain. The study of these boosters and a new vaccine formulation is still ongoing.

The pre-print study has not been through the peer-review process. Once more data is available and analysis is complete, a peer-reviewed publication is expected.

Update on May 3, 2021: On May 3, 2021, Moderna announced an agreement with the health partnership Gavi to supply up to 500 million doses of the COVID-19 vaccine. The doses will be for low-and middle-income countries as part of the COVAX Facility.

On April 30th, 2021, the World Health Organization (WHO) issued Emergency Use Listing (EUL) for indiviuals 18 and older.

Update on April 2, 2021: On March 29th, 2021, Moderna announced that it had shipped its 100 millionth dose of the vaccine to the U.S. government.

On April 1st, 2021, Moderna announced U.S. Food and Drug Adminstration approval for vials of the vaccine can be kept at room temperature for administration for up to 24 hours (up from 12 hours previously). They also approved the vaccine to be useable for up to 12 hours at room termperature (up from 6 hours previously). Finally, they also approved a new vial to hold 15 doses of the vaccine and expanded the current vial requirement to hold 11 doses (up drom 10 previously).

The Moderna COVID-19 vaccine is an mRNA vaccine with an efficacy rate of 94.1% in clinical trials. After completing several clinical trials, this vaccine has been approved for emergency use authorization in dozens of countries around the world.

The Moderna COVID-19 vaccine is an mRNA vaccine with an efficacy rate of 94.1% in clinical trials. After completing several clinical trials, this vaccine has been approved for emergency use authorization in dozens of countries around the world.

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What our experts say

The Moderna vaccine is being developed and produced by Moderna, Inc. and is a genetic mRNA vaccine (mRNA-1273) currently in ongoing Phase 3 clinical trials in the U.S. and a Phase 1/2 trial in Japan (announced January 21, 2021). This vaccine is approved for emergency use in US (United States Food and Drug Administration)(December 18, 2020), Canada (Health Canada) (December 23, 2020), Israel (Israel's Ministry of Health)(January 4, 2021), the European Union (European Medicines Agency) (January 6, 2021), the United Kingdom (Medicines and Healthcare Products Regulatory Agency)(January 8, 2021), Switzerland (SwissMedic) (January 12, 2021), Singapore (Singapore Health Sciences Authority)(February 3, 2021), Qatar (Qatar Ministry of Public Health)(February 11, 2021). Here's a breakdown of everything you need to know so far about this vaccine's development.

Collaborators: Moderna is collaborating with Biomedical Advanced Research and Development Authority and the National Institute of Allergy and Infectious Diseases (NIAID) on vaccine development and testing for the vaccine.

Latest information on how well the vaccine works: Primary efficacy analysis data from the Phase 3 trial was published on November 30, 2020 and further peer-reviewed analysis was published on December 30, 2020. In both papers, the experimental COVID-19 vaccine was reported to have 94.1% efficacy. Protection against severe COVID-19 was reported at 100%.

The study recorded a total of 196 infections among the 30,420 trial participants who received either the vaccine or a placebo (injections of saltwater). Of the 196 infections, 11 occurred among those who received the experimental (mRNA-1273) vaccine, and 185 infections occurred among those who did not receive the experimental vaccine (participants in the placebo group). Of the 30 severe cases of COVID-19 reported in the study, all were in the placebo group. There has been one COVID-19-related death in the study, which occurred in the placebo group.

The results published in late November and late December are consistent with the first interim analysis conducted during the study (announced on November 16th, 2020) that reported efficacy of 94.5%. In a "Letter to the Editor" published in the New England Journal of Medicine on December 3, 2020, Moderna shared interim analysis findings from their Phase 1 trial that suggested that at "day 119" (119 days following a patient's first vaccine dose; 90 days after the second vaccine dose), binding and neutralizing antibody titers remained high in Phase 1 patients across age groups. In other words, the results suggested ongoing immunity, although precise levels for protection against COVID-19 have not yet been established.

On January 25, 2021, Moderna announced the submission of a preprint study with results from an in vitro (laboratory-based) study suggesting the vaccine protects against new COVID-19 variants (B.1.1.7 first identified in the United Kingdom and B.1.351 first identified in the Republic of South Africa). The press release states that the vaccine "produced neutralizing titers [neutralizing antibodies] against all key emerging variants tested." However, the level of immunity against the B.1.351 variant was far less than the protection provided against earlier variants. To provide additional protection, Moderna plans to test another booster (injection) of the mRNA-1273 vaccine to see if immunity can be increased. Moderna is also beginning a preclinical study and a US-based Phase 1 trial of a new vaccine (mRNA-1273.351) specifically aimed at increasing immunity against the new variant by boosting strain-specific spike proteins.

Distribution timeline: Applications for US FDA Emergency Use Authorization and Conditional Marketing Authorization (CMA) with the European Medicines Agency (EMA) were filed on November 30th, 2020. Safety and efficacy data was reviewed by the U.S. regulators an an Emergency Use Authorization was issued on December 18, 2020. Additional international approvals and distribution plans are further detailed in the following sections.

Approvals: This vaccine is approved for emergency or interim use in individuals 18 years of age and older in the U.S. (United States Food and Drug Administration)(December 18, 2020), Canada (Health Canada) (December 23, 2020), Israel (Israel's Ministry of Health)(January 4, 2021), the European Union (European Medicines Agency) (January 6, 2021), the United Kingdom (Medicines and Healthcare Products Regulatory Agency)(January 8, 2021), Switzerland (SwissMedic) (January 12, 2021), Singapore (Singapore Health Sciences Authority)(February 3, 2021), Qatar (Qatar Ministry of Public Health)(February 11, 2021), and the World Health Organization (WHO)(April 30, 2021). Additional authorizations are currently under review in other countries.

Distribution plan: As of February 16th, 2021, Moderna has supplied approximately 45.4 million doses to the U.S. government, and additional doses have been supplied to Canada, the U.K. and the EU. Moderna expects to supplied 100 million doses to the U.S. as of March 29, 2021, and plans to deliver another 100 million doses by the end of May 2021 and another by the end of July 2021 (for a total of 300 million doses planned for the US). At the start of 2021, the company reported that they plan to manufacture 600 million doses globally in 2021, and that it is continuing to invest with the goal of supplying 1 billion doses during 2021. As of February 17th, 2021, the EU has purchased 310 million doses of the vaccine for delivery in 2021 with an option for another 150 million to be delivered in 2022. Pending approval in Japan, Moderna has said that they plan to distribute 50 million doses in the first half of 2021. Pending approval in the Philippines, Moderna has contracted with the government to supply 13 million doses of the vaccine under an agreement announced on March 6, 2021.

How the vaccine is being studied: Vaccines are tested and studied in multiple phases (phased testing) to determine if they are safe and work to prevent illness. Before a vaccine is tested on humans, in the preclinical phase it is tested on laboratory cells or animals. Once it is approved for human research, there are three phases that take place before the vaccine can be considered for approval for public use. During the first stage (Phase I), the new vaccine is provided to small groups of people—the first time the vaccine is tested in humans. The second stage (Phase II) involves testing the vaccine on people who have similar characteristics (such as age and physical health) to the target population, or the group for which the vaccine is intended. The goal of this stage is to identify the most effective dosages and schedule for Phase III trials. The final stage (Phase III) provides the vaccine to thousands of people from the target population to see how safe and effective it is. Once the vaccine has undergone Phase 3 testing, the manufacturer can apply for a license from regulatory authorities (like the FDA in the US) to make the vaccine available for public use. Once approved, the drugmaker will work with national governments and international health organizations to monitor vaccine recipients for potential side effects from the vaccine that were not seen in clinical trials (this is called surveillance). This phase also helps researchers understand how well a vaccine works over a longer time frame and how safe it is for the population.

Type of vaccine: The mRNA-1273 vaccine is what scientists are calling a genetic mRNA vaccine. This type of vaccine works by using genetic information from the coronavirus once it is injected into the body. The genetic information enters into human cells, instructs the body to make special spike proteins like the coronavirus, and causes the immune system to respond.

Dosage: In the current Phase 3 clinical trial, participants receive two injections of 100 micrograms each into their upper arm muscle. The injections are given 28 days apart. If approved, researchers expect that the same dosage and schedule will be prescribed to the public.

Vaccine storage conditions: Storage requirements are important to consider for new vaccines. In order for vaccines to be safe and effective, they must be held at the correct temperature during distribution and storage in health centers, pharmacies, and clinics. Maintaining the correct storage temperature can be difficult, especially if the vaccine's temperature requirement is very cold. The Moderna vaccine can be stored in a standard refrigerator temperature range (2 to 8 degrees Celsius or 36 to 46 degrees Fahrenheit) for up to 30 days. The vaccine can also be kept in long-term storage at a standard freezer temperature (-20 degrees Celsius or -4 degrees Fahrenheit) for up to six months. Maintaining these storage temperatures is already possible across vaccine distribution channels.

On April 1st, 2021, Moderna announced U.S. Food and Drug Adminstration approval for vials of the vaccine can be kept at room temperature for administration for up to 24 hours (up from 12 hours previously). They also approved the vaccine to be useable for up to 12 hours at room termperature (up from 6 hours previously). Finally, they also approved a new vial to hold 15 doses of the vaccine and expanded the current vial requirement to hold 11 doses (up drom 10 previously).

Preclinical testing: Before testing could begin on humans, the trial vaccine was tested on primates. Vaccine doses of 10 micrograms or 100 micrograms of the experimental vaccine were tested. On July 28, 2020, results were published and showed that the vaccine was protective against COVID-19. The vaccine was then permitted to advance to clinical trials in humans.

Phase 1 trial: The first patient dose of mRNA-1273 was given on March 16, 2020 and results from the Phase 1 trial were published on July 14, 2020. The Phase 1 trial included 45 participants, between age 18 and 55, who received two vaccine doses each, 28 days apart. Participants were divided into 3 groups (of 15 each) to test vaccine doses: 25 micrograms (two doses of 25 micrograms each given 28 days apart), 100 micrograms (two doses of 100 micrograms each given 28 days apart), and 250 micrograms (one dose). By day 43 of the trial, researchers observed immune responses in all participants that could reduce the ability of COVID-19 to infect people by 80% or more. By day 57, participants who received 100 microgram doses of the vaccine had average levels of neutralizing antibodies (special proteins that disable viruses in the body) that were about twice the average levels found in patients who have recovered from COVID-19. On day 119 (119 days following the first vaccine dose; 90 days after the second vaccine dose), binding and neutralizing antibody titers remained high in Phase 1 patients across age groups. These titers suggest ongoing immunity, though precise levels for protection against COVID-19 have not yet been established yet.

Phase 2 trial: Phase 2 approval was given on May 6th, 2020, and the Phase 2 trials started on May 29th, 2020. Phase 2 evaluated the two doses of 50 micrograms (given as two injections of 50 micrograms each) and 100 micrograms (given as two injections of 100 micrograms each). On June 11th, 2020, recruitment of participants was completed with a total of 300 participants between 18 and 55 years of age (50 total participants were over 55 years of age). On September 29th, 2020, Phase 2 findings were published and examined the immune responses for the vaccine in 40 older adults at different doses. The study examined two different vaccine doses (25 micrograms and 100 micrograms given in two doses each, 28 days apart) and found that the higher dose (100 micrograms) produced a greater antibody titer (immune) response in the older adult population.

Phase 1/2 trial: On January 21, 2021, Moderna announced that a new combined Phase 1/2 study of 200 adult patients was being launched with Takeda Pharmaceuticals in Japan. Similar to prior studies, the study will evaluate the safety and immune response to two doses (100 micrograms each) of the mRNA-1273 vaccine given 28 days apart. Participants will be monitored for 12 months following the second vaccine.

Phase 3 trial: This clinical study was registered as a randomized, placebo controlled trial (participants are selected for participation and randomly assigned to either receive the experimental vaccine or a placebo injection) on July 14th, 2020, and the study began on July 27, 2020 in study centers across the US. The total Phase 3 study enrollment was 30,420 participants age 18 and older (15,210 in the study group and the same number in the placebo group). On October 22, 2020 the company announced that recruitment was complete, and that 25,650 participants had already received two shots. 37% of study participants were from Communities of Color (>11,000 total with >6,000 who identify as Hispanic or LatinX, >3,000 who identify as Black or African American), and 42% were from populations considered high risk (7,000 Americans over the age of 65, and 5,000 who are under the age of 65 but have high-risk chronic diseases including diabetes, severe obesity, and cardiac disease that put them at higher risk of COVID-19). During the study, 96% of the study participants received both injections. Data collection from the Phase 3 trial is ongoing and will continue for two years; efficacy results are noted in the findings section above with current a efficacy of 94.1% (as published in the Efficacy and Safety of the mRNA-1273 SARS-CoV-2 Vaccine paper in the New England Journal of Medicine on December 30, 2020). Efficacy results as reported were consistent across age, race and ethnicity, and gender.

Booster vaccine to address the variant first identified in the Republic of South Africa: On March 10, 2021, Moderna announced that the first patients had been dosed with a booster vaccine (mRNA-1273.351) targeted against preventing infection with the COVID-19 variant first identified in the Republic of South Africa. The study includes three groups: 20 micrograms of mRNA-1273.351 (n=20), 50 micrograms of mRNA-1273.351 (n=20), and 50 micrograms of mRNA-1273.211, which combines the approved mRNA-1273 vaccine and the mRNA-1273.351 booster in a single vaccine (n=20).

A pre-print study entered on May 5th, 2021 reported on early results from phase 2 research on Moderna's booster vaccines. The boosters are shots given to people who had received both doses of the Moderna vaccine (mRNA-1273) about 6 months earlier. One booster, mRNA-1273.351, is aims to protect patients from the COVID-19 variant first identified in the Republic of South Africa (B.1.351). The other booster is a smaller dose (50 micrograms) of the existing mRNA-1273 vaccine.

Blood from patients who received the boosters was analyzed in the lab and showed a good response in fighting against ("neutralizing") the variants B.1.351 (first identified in the Republic of South Africa) and P1 (first identified in Brazil). The boosters have been reported to meet safety standards with side effects similar to those reported in earlier mRNA vaccine studies. Side effects were generally mild and included pain at the injection site, fatigue, headache, muscle pain, and joint pain. The study of these boosters and a new vaccine formulation is still ongoing.

The pre-print study has not been through the peer-review process. Once more data is available and analysis is complete, a peer-reviewed publication is expected.

New vaccine testing: On March 15, 2021, Moderna announced that the first patients had been dosed for a new Phase 1 study of mRNA-1283, a new vaccine aimed at preventing COVID-19. This new vaccine is refrigerator-stable, which may make distribution easier around the world. The study is evaluating three dose levels (10 micrograms, 30 micrograms, and 100 micrograms) given as two doses, 28 days apart. It is also studying a single dose of 100 micrograms. Data collection is ongoing.

Reported side effects and safety concerns: No safety concerns have been reported in the Phase 3 study, and most side effects have been mild to moderate in severity. Severe concerns that have occurred in >2% of cases include injection site pain (reported by 86% or participants), fatigue, muscle aches and headache. In the Phase 1 trial, side effects including fatigue, chills, headache, muscle aches, and pain at the injection site were commonly reported, particularly after the second vaccine dose. In the early phases of research, participants who received the highest vaccine dose (250 micrograms) had more severe side effects than those in the other experimental groups. The most commonly reported severe symptoms included fatigue, fever (39-40 degrees C), and chills (significant, prevents daily activities).

Special populations: On December 2, 2020, Moderna registered a new Phase 2/3 (combined phases) randomized, placebo controlled study with plans to enroll 3,000 healthy adolescents between 12 and <18 years of age from across the US. On December 10, 2020, Moderna announced that the first participants had received the experimental vaccine. Using the same dosing schedule as adults (two injections of 100 micrograms each given 28 days apart), the study aims to evaluate the safety and efficacy of the vaccine (including the type of side effects participants experience and the frequency of those events). The estimated study completion date is June 30, 2022. On March 16, 2021, Moderna announced that the first patients had been vaccinated in a new Phase 2/3 study called KidCOVE. The study plans to enroll 6,750 patients between the age of six months and 12 years. In the first part of the study, doses will be tested to determine which dose will be used in the placebo-controlled part of the study (part 2). Safety and immune response will be the primary endpoints evaluated. The mRNA-1273 vaccine has not yet been tested on pregnant or lactating women or other special groups (e.g., immunocompromised patients), though widespread community-based vaccine efforts have included these patients.

Other relevant notes: N/A

Context and background

Over 165 vaccines against the coronavirus are in development around the world, and approximately 54 are in human trials. Moderna was the first American company to test a vaccine in humans, and is the second U.S. drugmaker to report successful preliminary results from a phase 3 trial. Moderna’s vaccine trials are part of the U.S. government’s Operation Warp Speed program, and received approximately $1 billion from the U.S. government in funding to support the research and development of the vaccine. 

Resources

  1. A Study to Evaluate the Safety, Reactogenicity, and Effectiveness of mRNA-1273 Vaccine in Adolescents 12 to <18 Years Old to Prevent COVID-19 (TeenCove)(Clinicaltrials.gov)
  2. A Study to Evaluate Efficacy, Safety, and Immunogenicity of mRNA-1273 Vaccine in Adults Aged 18 Years and Older to Prevent COVID-19 (ClinicalTrials.gov)
  3. An mRNA Vaccine against SARS-CoV-2 — Preliminary Report (NEJM) (Supplementary Appendix- NEJM)
  4. Moderna’s COVID-19 Vaccine Candidate Meets its Primary Efficacy Endpoint in the First Interim Analysis of the Phase 3 COVE Study (Moderna)
  5. Moderna Announces Longer Shelf Life for its COVID-19 Vaccine Candidate at Refrigerated Temperatures (Moderna)
  6. Moderna Announces First Participants in Each Age Cohort Dosed in Phase 2 Study of mRNA Vaccine (mRNA-1273) Against Novel Coronavirus (Moderna)
  7. Moderna Completes Enrollment of Phase 2 Study of its mRNA Vaccine Against COVID-19 (mRNA-1273) (Moderna)
  8. Moderna Completes Enrollment of Phase 3 COVE Study of mRNA Vaccine Against COVID-19 (mRNA-1273) (Moderna)
  9. Vaccine experts say Moderna didn’t produce data critical to assessing Covid-19 vaccine (STAT News)
  10. Evaluation of the mRNA-1273 Vaccine against SARS-CoV-2 in Nonhuman Primates (NEJM)
  11. Moderna’s Work on a COVID-19 Vaccine Candidate (Moderna)
  12. First data for Moderna Covid-19 vaccine show it spurs an immune response (STAT News)
  13. Will Moderna Match Competitors’ Covid-19 Vaccine Prices? (Forbes)
  14. Safety and Immunogenicity of SARS-CoV-2 mRNA-1273 Vaccine in Older Adults (NEJM)
  15. We can stop COVID-19: Moderna vaccine success gives world more hope (Reuters)
  16. Moderna: Covid vaccine shows nearly 95% protection (BBC)
  17. Early Data Show Moderna’s Coronavirus Vaccine Is 94.5% Effective (NYT)
  18. Moderna Announces Primary Efficacy Analysis in Phase 3 COVE Study for Its COVID-19 VaccineCandidate and Filing Today with U.S. FDA for Emergency Use Authorization (Moderna)
  19. Durability of Responses after SARS-CoV-2 mRNA-1273 Vaccination (NEJM)
  20. Moderna Announces First Participants Dosed in Phase 2/3 Study of COVID-19 Vaccine Candidate in Adolescents (Moderna)
  21. FDA Takes Additional Action in Fight Against COVID-19 By Issuing Emergency Use Authorization for Second COVID-19 Vaccine (US FDA)
  22. Israeli Ministry of Health Authorizes COVID-19 Vaccine Moderna for Use in Israel (Moderna)
  23. Moderna Provides COVID-19 Vaccine Supply Update (Moderna)
  24. Efficacy and Safety of the mRNA-1273 SARS-CoV-2 Vaccine (NEJM)
  25. European Commission Authorizes COVID-19 Vaccine Moderna in Europe (Moderna)
  26. United Kingdom Medicines and Healthcare products Regulatory Agency Authorizes Use of COVID-19 Vaccine Moderna (Moderna)
  27. Swissmedic Authorizes COVID-19 Vaccine Moderna for Use in Switzerland (Moderna)
  28. Moderna Announces First Participant Dosed in Phase 1/2 Study of Moderna COVID-19 Vaccine in Japan Led by Takeda (Moderna)
  29. Moderna COVID-19 Vaccine Retains Neutralizing Activity Against Emerging Variants First Identified in the U.K. and the Republic of South Africa (Moderna)
  30. mRNA-1273 vaccine induces neutralizing antibodies against spike mutants from global SARS-CoV-2 variants (bioRxiv)
  31. Moderna Provides U.S. COVID-19 Vaccine Supply Update (Moderna)
  32. Moderna Confirms Discussions with U.S. Government for Additional 100 Million Doses of the Moderna COVID-19 Vaccine (Moderna)
  33. Interim recommendations for use of the Moderna mRNA-1273 vaccine against COVID-19 (WHO)
  34. Singapore Health Sciences Authority (HSA) Approves Interim Authorization of COVID-19 Vaccine Moderna For Use (Moderna)
  35. Qatar Ministry of Public Health Issues Emergency Use Authorization for COVID-19 Vaccine Moderna (Moderna)
  36. Moderna Provides U.S. COVID-19 Vaccine Supply Update (Moderna)
  37. European Commission Purchases Additional 150 Million Doses of COVID-19 Vaccine Moderna (Moderna)
  38. Moderna Announces New Drug Application Submitted to Import and Distribute Moderna’s COVID-19 Vaccine Candidate in Japan (Moderna)
  39. Moderna Announces Supply Agreement to Provide 13 Million Doses of COVID-19 Vaccine Moderna to the Philippines (Moderna)
  40. Moderna Announces First Participants Dosed in Study Evaluating COVID-19 Booster Vaccine Candidates (Moderna)
  41. First Participants Dosed in Phase 1 Study Evaluating mRNA-1283, Moderna’s Next Generation COVID-19 Vaccine (Moderna)
  42. Moderna Announces First Participants Dosed in Phase 2/3 Study of COVID-19 Vaccine Candidate in Pediatric Population (Moderna)
  43. Moderna Provides Storage Update & Announces the U.S. FDA Authorizes Up To 15-Doses Per Vial of its COVID-19 Vaccine (Moderna)
  44. Moderna Announces Shipment of 100 Millionth Dose of its COVID-19 Vaccine to the U.S. Government (Moderna)
  45. Moderna Announces Emergency Use Listing Granted by the World Health Organization for its COVID-19 Vaccine (Moderna)
  46. Moderna Announces Supply Agreement with Gavi for up to 500 Million Doses of COVID-19 Vaccine Moderna for COVAX To Help End COVID-19 Pandemic in Lowest Income Countries (Moderna)
  47. WHO lists Moderna vaccine for emergency use (World Health Organization)
  48. Preliminary Analysis of Safety and Immunogenicity of a SARS-CoV-2 Variant Vaccine Booster (medRxiv)

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