The original formula of COMIRNATY was developed to help protect against the original virus strain that caused COVID-19.

People in this study 12 years of age and older received a 2-dose series of the original formula of COMIRNATY 3 weeks apart (referred to as the primary series). This group was compared to people who were unvaccinated (received placebo) and had no prior history of COVID-19.

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The Main COMIRNATY Clinical Trial Was One of the Largest Vaccine Trials Conducted by Pfizer

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The multicenter, randomized, placebo-controlled trial evaluated the efficacy and safety of COMIRNATY in a diverse population of ~46,000 people 12 years of age and older.

The age, gender, race, and ethnicity of people in the placebo and vaccine groups of the efficacy analyses were similar, as were the characteristics between people in the safety populations.

The primary efficacy analysis (through November 14, 2020) included 36,621 people 12 years of age and older (18,242 in the COMIRNATY group and 18,379 in the placebo group).

The updated efficacy analysis (through March 13, 2021) included approximately 40,000 people 16 years of age and older (19,993 in the COMIRNATY group and 20,118 in the placebo group).

Then, a separate* efficacy analysis (through September 2, 2021) was done in 2260 people who were 12 through 15 years of age (1131 in the COMIRNATY group and 1129 in the placebo group).

*This was a supplemental analysis that was not a planned analysis of the study.

The study excluded people who were immunocompromised and those who were previously diagnosed with COVID-19. The efficacy analysis included people with preexisting stable disease, defined as disease not requiring significant change in therapy or hospitalization for worsening disease during the 6 weeks before enrollment, were included as were participants with known stable infection with HIV, hepatitis C virus (HCV), or hepatitis B virus (HBV).

Study Population

Among people 16 years of age and older in the updated efficacy analysis who received COMIRNATY or placebo:
Characteristic COMIRNATY Placebo
Sex (%)
Male 51.4 50.3
Female 48.6 49.7
Age group (%)
16 through 64 years 79.1 79.2
65 years or older 20.9 20.8
Race or ethnic group (%)
White 81.9 82.1
Black or African American 9.5 9.6
American Indian or Alaska Native 1.0 0.9
Asian 4.4 4.3
Native Hawaiian or other Pacific Islander 0.3 0.2
Hispanic or Latino 25.6 25.4
Non-Hispanic/Latino 73.9 74.1
Did not report ethnicity 0.5 0.5
Comorbidities (%)
Have 1 or more that increase the risk of severe COVID-19 disease 46.0 45.7
Age at vaccination (years)
Mean 49.8 49.7
Median 51.0 51.0
Among the participants 12 through 15 years of age, 50.1% were male and 49.9% were female, 85.8% were White, 4.6% were Black or African American, 11.7% were Hispanic/Latino, 6.4% were Asian, and 0.4% were American Indian/Alaska Native.

Study Objectives

In the main COMIRNATY trial, the efficacy and safety objectives were:

For people 16 years of age and older

  • Vaccine efficacy against confirmed symptomatic COVID-19*
  • Vaccine efficacy against severe COVID-19
  • Safety assessment, based on solicited specific local or systemic adverse events, and unsolicited adverse events and serious adverse events

*From 7 days after their second dose.

For people 12 through 15 years of age

  • Vaccine efficacy against confirmed symptomatic COVID-19*
  • Safety assessment, based on solicited specific local or systemic adverse events, and unsolicited adverse events and serious adverse events

*From 7 days after their second dose.

Safety

Possible serious risks
Safety findings from clinical trials as well as findings following FDA authorization and approval found the following possible serious risks:
  • Severe allergic reactions
  • Myocarditis (inflammation of the heart muscle)
  • Pericarditis (inflammation of the lining outside the heart)
  • Fainting after vaccination
  • Reduced immune response in people with weakened immune systems
Learn more about Important Safety Information
In the main COMIRNATY clinical trial, in people 12 through 15 years of age who had received at least 1 dose of COMIRNATY or placebo:

Serious adverse events were reported by 0.9% (n=10) of COMIRNATY recipients and 0.2% (n=2) of placebo recipients.

With primary series, the most commonly reported adverse reactions (≥8%) following any dose were:

  • Pain at the injection site (90.5%)
  • Fatigue (77.5%)
  • Headache (75.5%)
  • Chills (49.2%)
  • Muscle pain (42.2%)
  • Fever (24.3%)
  • Joint pain (20.2%)
  • Injection site swelling (9.2%)
  • Injection site redness (8.6%)
Learn more about Important Safety Information
In the main COMIRNATY clinical trial, in people 16 through 55 years of age who had received at least 1 dose of COMIRNATY or placebo:

Serious adverse events were reported by 0.8% (n=103) of COMIRNATY recipients and 0.9% (n=117) of placebo recipients.

With primary series, the most commonly reported adverse reactions (≥10%) following any dose were:

  • Pain at the injection site (88.6%)
  • Fatigue (70.1%)
  • Headache (64.9%)
  • Muscle pain (45.5%)
  • Chills (41.5%)
  • Joint pain (27.5%)
  • Fever (17.8%)
  • Injection site swelling (10.6%)
Learn more about Important Safety Information
In the main COMIRNATY clinical trial, in people 56 and older who had received at least 1 dose of COMIRNATY or placebo:

Serious adverse events were reported by 1.8% (n=165) of COMIRNATY recipients and 1.7% (n=151) of placebo recipients.

With primary series, the most commonly reported adverse reactions (≥10%) following any dose were:

  • Pain at the injection site (78.2%)
  • Fatigue (56.9%)
  • Headache (45.9%)
  • Muscle pain (32.5%)
  • Chills (24.8%)
  • Joint pain (21.5%)
  • Injection site swelling (11.8%)
  • Fever (11.5%)
  • Injection site redness (10.4%)
Learn more about Important Safety Information
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