COVID-19 vaccine clinical trials

 

Clinical trials were conducted to assess the safety and efficacy of the COVID-19 vaccines.

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Pfizer Canada / BioNTech Vaccine Trial

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Between July 27 - November 14, 2020, 43,548 people were recruited from 152 sites worldwide and randomized to receive placebo or the COVID-19 vaccine. Key inclusion criteria for this trial included age above 16 years and being in healthy condition. Key exclusion criteria for this trial included a medical diagnosis of COVID-19, medical diagnosis of an immunocompromising condition, and women who were pregnant or breastfeeding. 

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The conclusion of this clinical trial was that a two-dose regimen of the Pfizer/BioNTech vaccine (30 μg per dose, given 21 days apart) was found to be safe and 95% effective against COVID-19 infection.

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What does ​95% efficacy mean? In this clinical trial, 0.74% of participants who received the placebo became infected with COVID-19, while 0.04% of participants who received the COVID-19 vaccine became infected with COVID-19. To calculate vaccine efficacy, you divide the difference between these infection rates (0.74 - 0.04 = 0.7) by the infection rate in the placebo group (0.74). This equals 0.0945, (0.7 / 0.74), or 95%. This means that people who received the COVID-19 vaccine had a 95% lower risk of becoming infected with COVID-19, relative to people who received the placebo.

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Moderna Therapeutics Vaccine Trial

 

Between July 27 - October 23, 2020, 30,420 people were recruited from 99 sites in the United States and randomized to receive placebo or the COVID-19 vaccine. Key inclusion criteria for this trial included age above 18 years and being in healthy condition. Key exclusion criteria for this trial included a medical diagnosis of COVID-19, medical diagnosis of an immunocompromising condition, and women who were pregnant or breastfeeding. 

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The conclusion of this clinical trial was that two injections of mRNA-1273 vaccine (100 μg per dose, given 28 days apart) showed 94.1% efficacy at preventing COVID-19 illness in a diverse adult trial population, and no safety concerns were identified, aside from short lived local and systemic reactions.

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 AstraZeneca Vaccine Trial

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Between April 23 - November 4, 2020, 11,636 people were recruited from the United Kingdom, Brazil and South Africa. Participants were randomized to receive placebo or the COVID-19 vaccine. Key inclusion criteria for this trial included age above 18 years and being in healthy condition. Key exclusion criteria for this trial included a medical diagnosis of COVID-19, medical diagnosis of an immunocompromising condition, and women who were pregnant or breastfeeding. 

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The conclusion of this clinical trial was that two injections of ChAdOx1 nCoV-19 vaccine showed 70.4% efficacy at preventing symptomatic COVID-19 illness, and that one injection of ChAdOx1 nCoV-19 vaccine showed 64.1% efficacy. No safety concerns were identified. 

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Janssen (Johnson & Johnson) Vaccine Trial

44,325 people were recruited from Argentina, Brazil, Chile, Colombia, Mexico, Peru, South Africa, and the United States. Participants were randomized to receive placebo or the COVID-19 vaccine. Key inclusion criteria for this trial included age between 18 - 55 and being in healthy condition. Key exclusion criteria for this trial included a medical diagnosis of COVID-19, medical diagnosis of an immunocompromising condition, and women who were pregnant or breastfeeding. 

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The results from the interim analysis of this clinical trial was that one injection of Ad.26.COV2.S vaccine showed 66% efficacy at preventing moderate and severe COVID-19, and no safety concerns were identified.

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Recommendations for COVID-19 vaccination of pregnant or breastfeeding women

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As pregnant and breastfeeding women were excluded from the COVID-19 vaccine clinical trials, there is currently no data evaluating the safety and efficacy of the two COVID-19 mRNA vaccines in pregnant and breastfeeding women. Pregnant women have also been largely excluded from clinical trials investigating how to treat patients with COVID-19. This is especially concerning, as pregnant women are considered to be at higher risk of COVID-19 infection, relative to the general population.

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On February 18th, 2021, Pfizer/BioNtech announced that they will begin an international clinical trial to evaluate the safety and effectiveness of the COVID-19 vaccine in pregnant women. The trial will first recruit 350 pregnant women between 27 and 34 weeks of pregnancy, before moving onto the larger trial of pregnant women between 24 and 34 weeks of pregnancy.

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On March 5th, 2021, the Ontario government identified pregnant women as a high-risk population eligible for COVID-19 vaccination in Phase Two of the provincial vaccination distribution plan. Pregnant women can expect to be vaccinated from April to July 2021.

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Below is a summary of the current COVID-19 vaccine recommendations for pregnant or breastfeeding women.

 

The Government of Canada, January 12th, 2021:

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• The COVID-19 vaccine may be offered to pregnant and breastfeeding women if the benefits of receiving the vaccine outweigh any potential risks

• Pregnant and breastfeeding women considering the vaccine should have a conversation with their health care professional

• Eligible women who are postpartum or planning to become pregnant should be offered COVID-19 vaccination

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Society of Obstetricians and Gynaecologists of Canada, February 1st, 2021:

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• Pregnant or breastfeeding women should be offered vaccination if they are eligible and no contraindications exist

• The decision to receive the vaccine is based on women’s personal values and an understanding of the benefits and potential risks of vaccination

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American College of Obstetricians and Gynecologists, February 4th, 2021:

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• COVID-19 vaccines should not be withheld from pregnant individuals who meet criteria for vaccination

• COVID-19 vaccines should be offered to lactating individuals similar to non-lactating individuals

• A conversation between the patient and their clinical team may assist with decisions regarding the use of vaccines for the prevention of COVID-19

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Centers for Disease Control and Prevention, February 12th, 2021:

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• People who are pregnant or breastfeeding and part of a priority group recommended to receive the COVID-19 vaccine may choose to be vaccinated

• A conversation between pregnant patients and their clinicians may help them decide whether to get vaccinated

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Special Statement from Society of Obstetricians and Gynaecologists of Canada - April 16th, 2021

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As Canada experiences a third wave of COVID-19 infections, there are increasing numbers of very sick pregnant women with COVID-19 requiring hospital admission in Ontario, including ICU admission and mechanical ventilation support.

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This is an extremely alarming situation.

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The Society of Obstetricians and Gynaecologists of Canada released a special statement calling for the Ontario and other provincial governments to prioritize COVID-19 vaccination for pregnant women over 20 weeks of gestation.