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#303 CO-KID: Covid vaccine for kids

What are the benefits and harms of the available COVID-19 vaccines for children and adolescents?

Pfizer/BioNTech vaccine is 91% effective in preventing symptomatic COVID-19 in children 5-11 years. Both Pfizer/BioNTech and Moderna are 100% effective in adolescents at ~2 months. Real world evidence might differ. Both vaccines appear safe with primarily injection site reactions.

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  • Study participants mostly white and healthy, 2 doses given 21-28 days apart. Median follow-up ~2 months. Cases were symptomatic, laboratory confirmed COVID-19. Severe COVID-19 is defined as cardiac, respiratory, other end organ failure, or ICU admission.
    • Children:
      • Pfizer/BioNTech: Multi-country, blinded, randomized controlled trial (RCT) of 2268 children 5-11 years old.1
        • Efficacy: ≥7 days post second dose.
        • COVID-19 cases: 3 versus 16 (placebo), relative risk reduction (RRR): 91%.1
        • Severe COVID-19: None.1
        • Most cases occurred when Delta variant was predominant strain.1-3
      • Solicited adverse effects:1 Similar between 1st and 2nd doses.
        • Localized pain ~73%; redness: ~17%.
        • Fatigue: ~37% versus 28% (placebo).
        • Myalgia: 10% versus 7% (placebo).
        • Serious adverse effects: 0 versus 1 (placebo).
        • Myocarditis or anaphylaxis: None.
      • Moderna: Enrolling 6-months to 11-year-olds.4
        • Only immunogenicity currently reported.5
  • Adolescents:
    • Pfizer/BioNTech: Blinded RCT, 2600 American 12–15-year-olds.6
      • Efficacy: ≥7 days post second dose:
        • COVID-19 cases: 0 versus 18 (placebo), 100% RRR.
        • Severe COVID-19: None.
      • Subjects enrolled prior to Delta variant.2
      • Solicited adverse effects:
        • Localized pain: ~83% vaccine.
        • Fatigue: ~63% versus ~33% (placebo).
        • Headache: ~60% versus 31% (placebo).
    • Moderna: Blinded RCT, 3732 American 12–17-year-olds.7
      • Efficacy: ≥14 days post second dose:
        • COVID-19 cases: 0 versus 4 (placebo), 100% RRR.
        • Severe COVID-19: Not reported.
    • Solicited adverse effects:
      • Localized pain, redness, swelling: >90%.
      • Fatigue: ~58% versus ~33% (placebo).
      • Headache: ~58% versus ~35% (placebo).
  • National Advisory Committee on Immunization recommends 2 doses 8 weeks apart for children, adolescents, and adults.8-10 
    • Risks of COVID-19 in children <19 years:
      • Hospitalization: 0.5%, (12% required ICU).11
        • ~80% of admissions are in healthy children.12
    • Children can get “long COVID”, but likely lower rates than adults.13
  • Myocarditis after mRNA vaccines:
    • Highest in boys 16-19 years: excess risk ~14 per 100,000 doses.14
      • 75% occur after second dose.15
      • Females: ~10% male risk.15
    • Most cases are mild.13,15  
  • Net Benefit: For 12–17-year-old males, for every million doses, vaccination may:
    • Prevent 215 COVID-19 hospitalizations, 71 ICU admissions, 2 deaths.
    • Cause ~65 cases of myocarditis.14

Paul Humphries November 25, 2021

I will encourage all the families I encounter in my practice to get their kids vaccinated

Maria Marszal November 29, 2021


Janelle Piche December 7, 2021

Very good summary of data

Gajan Krishna January 3, 2022

Good review

Shiraz Shariff January 3, 2022

excellent cme

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  • Michael R Kolber BSc MD CCFP MSc
  • Paul Fritsch MD CCFP
  • Jennifer Young MD CCFP-EM
  • Alexander Singer MB BAO BCh CCFP
  • Tony Nickonchuk BScPharm

1. Walter EB, Talaat KR, Sabharwal C, et al. NEJM Nov 9, 2021. DOI: 10.1056/NEJMoa2116298

2. Pfizer. Vaccines and Related Biological Products Advisory Committee Briefing Document-BNT162B2 (COMIRNATY) Vaccine-26 October 2021.; Available at: Accessed Oct 28, 2021.

3. CDC COVID Data Tracker. Available at: Accessed October 29, 2021.

4. A Study to Evaluate Safety and Effectiveness of mRNA-1273 COVID-19 Vaccine in Healthy Children Between 6 Months of Age and Less Than 12 Years of Age. Available at. Accessed October 29, 2021

5. Moderna Announces Positive Top Line Data from Phase 2/3 Study of COVID-19 Vaccine in Children 6 to 11 Years of Age | Moderna, Inc. Available at: Accessed October 29, 2021.

6. Frenck Jr RW, Klein NP, Kitchin N, et al. NEJM 2021; DOI: 10.1056/NEJMoa2107456

7. Ali K, Berman G, Zhou H, et al. NEJM 2021; doi:10.1056/NEJMOA2109522

8. NACI recommendation on the use of the Pfizer-BioNTech COVID-19 vaccine (10 mcg) in children 5-11 years of age. 2021 Nov 19. Available at: Accessed November 22, 2021.

9. NACI recommendation on the use of mRNA COVID-19 vaccines in adolescents 12-17 years of age. Available at: Accessed November 22, 2021.

10. NACI Recommendation on the use of COVID-19 Vaccines. Available at : Accessed November 22, 2021.

11. Public Health Agency of Canada. Author’s calculations - COVID-19 daily epidemiology update - Available at: Accessed October 29, 2021.

12. Government of Alberta. Author’s calculations-COVID-19 Alberta vaccine outcome statistics | Available at: Accessed October 29, 2021.

13. Nickonchuk T, Kirkwood J, Dugre N, et al. Tools for Practice Long COVID. Available at: Accessed November 12, 2021.

14. Mevorach D, Anis E, Cedar N, et al. NEJM 2021; doi:10.1056/NEJMOA2109730

15. Gargano JW, Wallace M, Hadler SC, et al. MMWR Morb Mortal Wkly Rep. 2021; 70(27):977-982.

Authors do not have any conflicts of interest to declare.

Les auteurs n’ont aucun conflit d’intérêts à déclarer.