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Supporting Your Practice

COVID-19 Update – How Effective are Vaccines?

Dr. Mark Donaldson 
Associate Principal, Vizient Inc.

Having lagged behind many other countries in the early months of COVID-19 vaccinations, Canada is now among the leading countries when it comes to the percentage of the population inoculated with at least one dose. Currently we stand at #9 worldwide.

In this in-depth presentation, Dr. Mark Donaldson, Associate Principal at Vizient Inc., gives a well-informed overview of the vaccination effort so far, including key metrics on efficacy rates, the durability of individual vaccines, and the effectiveness of vaccines against variants. He also touches upon the potential benefits of heterologous vaccination, and details common vaccine side effects observed so far.

Here are some of the highlights from the presentation:

Vaccine Efficacy (Macro Population)

  • mRNA vaccines (Moderna & PfizerBioNTech) – approx. 95% efficacy
  • AstraZeneca – 76% efficacy
  • Out of > 95 million Americans who are fully vaccinated against COVID-19:
    • Only 6025 symptomatic breakthroughs (0.007%)
    • Only 0.0006% hospitalizations for COVID-19
    • Only 0.0001% deaths from COVID-19


  • Pfizer-BioNTech - 91.3% efficacy against symptomatic illness diagnosed from 1 week to 6 months after the second dose of vaccine.

Teen Population

  • Having decreased early in 2021, adolescent hospitalization rates for COVID-19 increased during March-April.
  • Pfizer BioNTech vaccine shown to be 100% effective in 12-15 year old children in Phase III clinical trial.
  • Vaccinations have now been approved for children aged above 12.


  • So far there have been 4 variants of the SARS-CoV-2 virus identified: Alpha, Beta, Gamma, and Delta.
  • Recent Moderna & Pfizer BioNTech trials show that mRNA vaccines in their current form are very effective against variants.

Heterologous Vaccination

  • Not a new concept. Combining different vaccine products may not only provide the same benefit, but possibly an enhanced benefit.

Vaccine Side Effects

  • Pregnant or lactating women – vaccines pose no additional risk to either the unborn fetus or breast feeding child. Spontaneous abortion was 12.6% among vaccinated, compared to 10%-26% in general population.
  • Facial Paralysis - According to an analysis in JAMA internal medicine, COVID-19 mRNA vaccines do not appear to pose any higher risk for facial paralysis than other viral vaccines.
  • Symptomatic Acute Myocarditis - low incidence has been reported involving seven cases in healthy male adolescents within four days of second dose of Pfizer BioNTech vaccination. Most cases were mild with no deaths. All patients resolved their symptoms rapidly. 

Vaccination and Virus Transmission  

  • Based on current data, fully vaccinated individuals cannot transmit the virus.

Flu Vaccine

  • Flu and COVID vaccines should be separated by 2 weeks.

We hope you find the conversation useful. We welcome your thoughts, questions and/or suggestions about this post and other topics. Leave a comment in the box below or send us your feedback by email.

Until next time!
CDA Oasis Team

Full Presentation (27.10")


  1. Vasant Ramlaggan June 24, 2021

    Thanks for the update on the stats. Very useful!

  2. Marie-Claude Lepage June 25, 2021

    Thanks for the information. Having this information from a reliable, scientific source is highly valuable!


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