Home South African LOOK: Comparing the Covid-19 vaccine efficacies

LOOK: Comparing the Covid-19 vaccine efficacies

Picture: Kelly-Jane Turner

There are six Covid-19 vaccines that have been approved for emergency or full use. However, they all differ in efficacy.

Vaccines have been hailed as the success story of the Covid-19 pandemic, where in under a year, scientists were able to create a vaccine to reduce the risk of getting the virus and help protect people from severe illness.

There are six Covid-19 vaccines that have been approved for emergency or full use by at least one WHO-recognised stringent regulatory authority. However, all of the vaccines available differ in efficacy.

According to the Gavi vaccine alliance, efficacy is the degree to which a vaccine prevents disease and possibly transmission under ideal and controlled circumstances.

Scientists are yet to determine vaccine effectiveness for the available vaccines.

“Vaccine effectiveness refers to how well it performs in the real world – including against new variants, and in people who may have been excluded from clinical trials, such as frail elderly individuals, or those taking drugs that suppress immune responses,” according to the alliance.

Efficacies of Covid-19 vaccines based on Clinical Trial Results. Graphic: The Gavi vaccine alliance.

Since the first Covid-19 vaccine was administered in December 2020, more than 5.4 billion doses have been administered worldwide.

In South Africa, two vaccines are available: Pfizer’s two dose jab and Johnson & Johnson’s single-dose vaccine.


The Pfizer Covid-19 vaccine has reached the final stages of full approval in the country, according to the South African Health Products Regulatory Authority (Sahpra).

Last month, the US Food and Drug Administration (FDA) granted full approval of Pfizer-BioNTech’s vaccine, making it the first coronavirus vaccine to move beyond emergency-use status.

Vaccine type and how it works: Pfizer’s mRNA Covid-19 vaccine works by delivering a tiny piece of genetic code from the SARS CoV-2 virus to host cells in the body. The vaccine teaches the body’s cell how to make a protein that triggers an immune response and produces antibodies which is what protects us from getting infected if the real virus enters the body.

Dosage: Pfizer is a two-dose vaccine. In South Africa, people can receive their second dose of 42 days or six weeks after their first dose. The vaccine is fully effective two weeks after the second shot.

Vaccine efficacy: Results from Pfizer’s initial Phase 3 clinical trial, which was presented in December 2020, showed the vaccine to have a 95% efficacy.

Possible vaccine side effects: Pain or swelling after injection of the arm, fatigue, headaches, muscle pain, chills, fever and nausea. These side effects happen within a day or two of getting the vaccine. They are normal signs that your body is building protection and should go away within a few days.

Johnson and Johnson

The Sisonke Johnson & Johnson implementation study examined the efficacy of the Johnson & Johnson Covid-19 vaccine between 17 February and 17 of May, where over 477 000 healthcare workers were vaccinated.

Co-principal investigator of the study, Professor Glenda Gray, revealed last month that the study found the J&J jab to be around 91-96% effective against death and was effective against the Delta variant.

Gray said the findings show that there is “remarkable protection” against Covid-19 hospitalisation and death.

Vaccine type and how it works: The J&J jab is a carrier, or virus vector, vaccine. Scientists engineer a harmless and inactivated adenovirus, similar to a common virus, as a shell to carry genetic code on the spike proteins to the cells. The inactivated virus does not infect a person with the virus, but the cells produce a spike protein to train the body’s immune system to recognise, react and create antibodies when the body is actually infected with Covid-19.

Vaccine efficacy: Clinical trials in the US showed the Johnson & Johnson vaccine has a 72% overall efficacy and 86% efficacy against severe disease.

Dosage: Currently, the J&J vaccine only requires one dose, however, the company announced last month that people who initially received the jab and then received the same one as a booster produced a much stronger antibody response than after receiving a single dose.

Possible vaccine side effects: Pain or swelling after injection of the arm, fatigue, headaches, muscle pain, chills, fever and nausea.

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