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Covid-19 Vaccines – Type, Safety, Efficacy, Trial Results, Approval, Side Effects

Here’s the consolidated information of the various Covid19 Vaccines available that have been approved for emergency use by selected countries. As of 22 June 2021, globally 3,888,361 people have died of COVID-19 (worldometers.info). Vaccines are a critical tool in the battle against COVID-19.

Approval for Emergency Use

Rigorous assessment of late phase clinical trial data are conducted to make sure that vaccines adhere to stringent criteria of safety, efficacy and quality reviewed by experts before they are given the green light for emergency use approval. The company producing the vaccine must continue to generate more data to enable full approval. Vaccine efficacy is defined as reduction percentage in disease incidence in a vaccinated group compared to an unvaccinated group under optimal conditions (randomized controlled trial) – [who.int].

On top of that, the drug control/ pharmaceutical authority of each country will evaluate the vaccines before they are approved to be used for their people.

Vaccines Type


The mRNA approach uses a section of genetic material that delivers the instructions to make the protein that our immune system responds to. No actual part of the microbe is used. Before the COVID-19 pandemic, none had yet been through the full approvals process for use in humans. The mRNA Covid-19 vaccines produced by BioNTech-Pfizer (more info below) and Moderna (Phase 3 Results published on nejm.org) reported high efficacy rate of more than 90% and minimal side effects. It requires extreme cold storage.

Inactivated Vaccine

This approach uses the disease-carrying microbe which has been killed/ inactivated. These vaccines are being used for a long time and proven safe to work in people. However it is not been proven that Inactivated vaccine such as Sinovac is more effective or safer than the others (like BioNTech or Moderna’s mRNA). Read Misinformation about Covid Vaccine. Available Inactivated Covid-19 Vaccines are:

    • China’s CoronaVac by Sivovac 
    • India’s Covaxin by Bharat Biotech
    • Sinopharm (China) Phase three trials: 79% effective. Phase three trial in United Arab Emirates (published on Journal of American Medical Association – JAMA): 78.1% effective. Approved by WHO for emergency use on 7th May 2021.

Viral Vector Vaccine

Uses a modified version of a different virus (the vector) to deliver important instructions to our cells to produce the harmless spike protein to trigger the immune system (cdc.gov). Viral Vector Covid-19 vaccines:

    • AstraZeneca/Oxford (Trial Results below) has an efficacy of 62-90%.
    • Janssen (Johnson & Johnson) has an overall efficacy of 66%, 85% effective in preventing severe disease after a single dose (JnJ Trial Results). Approved by WHO for emergency use on 12th Mar 2021.
    • Russia’s Viral Vector Gam-COVID-Vac by Sputnik V Efficacy is at 91.6%.
    • China’s single dose CanSinoBIO has an Efficacy of 65.7%. 

Variants (First Detected)

  • B.1.1.7 also known as the Alpha variant (UK)
  • B.1.351 also known as Beta (South Africa Dec 2020)
  • P.1 also known as Gamma (Brazil)
  • B.1.617.2 strain also known as Delta variant (India Dec 2020)

Adverse Reactions

[source: Medicines & Healthcare Regulatory Agency (MHRA)]

Most adverse reaction reports relate to injection-site reactions and generalised symptoms such as a ‘flu-like’ illness, headache, chills, fatigue, nausea, fever, dizziness, weakness, aching muscles, and rapid heartbeat. Generally, these reactions are not associated with more serious illness and likely reflect an expected, normal immune response to the vaccines. Many of adverse reactions reported do not have any relation to the vaccine and it is often coincidental that they both occurred around the same time. as they would have happened anyway even without vaccine.

As of 9 June 2021 in the UK:

Estimated first doses of vaccine administered and Cases of serious adverse reactions reported by Vaccine

Covid-19 VaccineEstimated first doses of vaccine administered (million doses)Adverse reactions associated with *anaphylaxis or anaphylactoidMajor thromboembolic events (blood clots) with concurrent thrombocytopenia (low platelet counts)
BioNTech/ Pfizer15.6376 
AstraZeneca24.6740390 (0.0016%)

To compare, according to FDA Drug Safety Communication: the risk of developing a blood clot for women who use birth control pills is 3-9 out of 10,000 women (0.03% – 0.09%)

*Anaphylaxis is a severe, potentially life-threatening allergic reaction that can occur within seconds or minutes of exposure to something you’re allergic to (mayoclinic)

List of Covid-19 Vaccines 

BNT162b2 (by Pfizer Inc. and BioNTech)

pfizer biontech logo

Pfizer Inc. and BioNTech’s safety and final efficacy results from the pivotal Phase 3 trial of BNT162b2, their mRNA-based COVID-19 vaccine candidate has been published on The New England Journal of Medicine (nejm.org on 31 Dec 2020). In the trial of 43,448 participants, who were 16 years and older, 21,720 of whom received BNT162b2 and 21,728 placebo, the two-dose regimen of 30 μg BNT162b2, which was given 21 days apart, was well-tolerated and demonstrated vaccine efficacy of 95% against COVID-19. There were 170 cases of COVID-19 observed with onset at least 7 days after the second dose; 8 cases occurred in vaccine recipients, and 162 in placebo recipients. Trial sites were in the United States, Argentina, Brazil, South Africa, Germany and Turkey. The incidence of serious adverse events was low and was similar in the vaccine and placebo groups.

Efficacy Calculation

Risk among vaccinated patients = 8/21720

Risk among unvaccinated patients (placebo) = 162/21728

Efficacy = 100×(1−[risk among vaccinated patients/risk among unvaccinated patients])

= 100*(1-(8/21720/(162/21728))) = 95%

Storage and Handling Summary

Recommended Storage Temperature: -70°C (±10°C)

The vaccine can be stored for five days at refrigerated 2-8°C conditions.

Type: mRNA

Interval between 2 doses: 21 days

Country: BioNTech (Germany) and Pfizer (USA)

Approval for children aged 12 to 15: USA (10 th May 2021) | Singapore (18th May 2021) | Hong Kong (3rd June) | UK (4th June 2021)

Approved for emergency use by WHO: 31 Dec 2020

Approvals and other Trials: Approved in 88 countries

Effectiveness against Variants: 88% effective two weeks after the second dose, against the B.1.617.2 (Delta) variant and 93% against B.1.1.7 (Alpha), known as the UK variant (British Medical Journal – bmj.com)

CoronaVac (by Sinovac)

sinovac logo

Some 25,000 participants enrolled in Sinovac’s Stage 3 clinical trials, which were conducted in Brazil, Turkey, Indonesia and Chile. After 14 days following vaccination with 2 doses of vaccine, the efficacy rate against diseases caused by COVID-19 was 50.65% for all cases, 83.70% for cases requiring medical treatment, and 100.00% for hospitalized, severe, and fatal cases (sinovac.com). Brazil and Turkey evaluated the efficacy of the vaccine in health care workers at higher risk of infections. According to Butantan Institute in Brazil, there have not been any serious adverse effects recorded. Sinovac’s lower efficacy rate can be due to their evaluation method. For example, Sinovac evaluated asymptomatic and very mild cases, while BioNTech only included symptomatic cases in their trial results.

Efficacy Rate of Phase 3 Trial in Brazil

The Brazilian Report

78% (Asymptomatic and very mild cases are not included)
50.4% (Asymptomatic and very mild cases are included)

Efficacy – Phase three trials Interim data

Turkey: 91.25%
Indonesia: 65.3%

Storage Temperature: 2-8°C (Standard Refrigerator)

Type: Inactivated Vaccine

Interval between 2 doses: 14 days

Country: China

Approved for emergency use by WHO: 1st June 2021

Approvals and other Trials: Approved in 29 countries

AstraZeneca-University of Oxford

astra zeneca oxford vaccine logo

This vaccine consists of a replication-deficient chimpanzee adenoviral vector, containing the SARS-CoV-2 structural surface glycoprotein antigen (spike protein; nCoV-19) gene. 11,636 participants (7548 in the UK, 4088 in Brazil) were included in the interim primary efficacy analysis. In participants who received two standard doses, vaccine efficacy was 62·1% and in participants who received a low dose followed by a standard dose, efficacy was 90·0% (Results published on thelancet.com). No serious safety concerns have emerged from the clinical trials.

Efficacy Rate: 62% – 90%

Storage Temperature: 2-8°C (Standard Refrigerator)

Type: Viral Vector Vaccine

Interval between 2 doses: 28 days – 12 weeks

Country: AstraZeneca (Sweden) and Oxford (British)

Approved for emergency use by WHO: 15 Feb 2021

Approvals and other Trials: Approved in 110 countries

Effectiveness against Variants: 60% effective against B.1.617.2 (Delta) at two weeks after the second dose and 66% against the Alpha (UK) variant (British Medical Journal – bmj.com).



(Phase 3 Results published on nejm.org)

The mRNA-1273 vaccine is a lipid nanoparticle–encapsulated mRNA-based vaccine that encodes the prefusion stabilized full-length spike protein of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes Covid-19.

Phase 3 randomized, observer-blinded, placebo-controlled trial 

The trial enrolled 30,420 volunteers across the United States, half (15,210 individuals) were randomly assigned to receive vaccine and the other half the placebo. Symptomatic Covid-19 illness was confirmed in 185 participants in the placebo group and in 11 participants in the mRNA-1273 group. The mRNA-1273 vaccine showed 94.1% efficacy at preventing Covid-19 illness, including severe disease. Moderate, transient reactogenicity (short-term common unfavorable reactions) after vaccination occurred more frequently in the mRNA-1273 group. Serious adverse events were rare, and the incidence was similar in the two groups.

Efficacy Rate: 94.1%

Storage Temperature: 50°C and -15°C 

Unpunctured vials may be stored in the refrigerator between 2° to 8°C (36° to 46°F) for up to 30 days.

Type: mRNA

Interval between 2 doses: 28 days apart

Country: USA

WHO lists Moderna vaccine for emergency use:  30 April 2021

Approvals and other Trials: Approved in 53 countries

Gam-COVID-Vac/ Gamaleya by Sputnik V

sputnik v covid vaccine russia

The efficacy rate of the adenoviral vector-based COVID-19 vaccine Gam-COVID-Vac in a randomised, double-blind placebo-controlled multicentre phase 3 trial in Moscow, Russia, including 21,862 participants, with a 21-day interval between the first dose and the second dose is 91.6%.

45 (0·3%) of 16,427 participants in the vaccine group and 23 (0·4%) of 5,435 participants in the placebo group had serious adverse events; none were considered associated with vaccination, with confirmation from the independent data monitoring committee. Four deaths were reported during the study (three [<0·1%] of participants in the vaccine group and one [<0·1%] of participants in the placebo group), none of which were considered related to the vaccine (thelancet.com).

Efficacy Rate: 91·6%

Storage Temperature: The vaccine is stored and distributed at –18°C, storage at 2–8°C (Standard Refrigerator)

Type: Viral Vector Vaccine

Interval between 2 doses: 21 days

Country: Russia

Approvals and other Trials: Approved in 68 countries

Ad5-nCoV by CanSinoBIO

cansinobio vaccine covid

CanSino Biologics Inc’s (CanSinoBIO) COVID-19 vaccine showed 65.7% efficacy in preventing symptomatic cases and a 90.98% success rate in stopping severe disease in an interim analysis of global trials. The CanSinoBIO vaccine is being tested in Pakistan, Mexico, Russia, Argentina and Chile, according to clinical trial registration data. The efficacy of the shot is based on analysis of 30,000 participants and 101 confirmed cases of COVID-19. No serious safety concerns have been raised in the study (Source)

Efficacy Rate: 65·7%

Storage Temperature: 2–8°C (Standard Refrigerator)

Type: Viral Vector Vaccine

Number of doses: 1 dose

Country: China

Approvals and other Trials: Approved in 5 countries

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