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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

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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.