In a major development in the ongoing fight against Coronavirus, the Ministry of Health and Prevention has approved Moderna’s COVID-19 vaccine for general use in the UAE. With this move, Moderna's vaccine has become the fifth vaccine to be approved by UAE authorities for public use in containing the spread of the virus. The ministry made the decision after the completion of clinical trials and an assessment and approval of the US Food and Drug Administration.

Here are details of the science behind every vaccine approved by the UAE health sector so far:

MODERNA

Approved by the UAE authorities on July 4, 2021, Moderna's vaccine has an efficacy rate of about 94 percent in preventing symptomatic infection. The mRNA vaccine requires two doses taken at a time gap of about 4 weeks. Some of the side effects of the vaccine may include headache, pain, chills, tiredness, redness, and swelling at the injection site. All these issues are generally resolved within a day or two.

The vaccine can be stored at regular freezer temperature and can be used within 30 days of thawing.

PFIZER-BIONTECH

Approved by the UAE on December 22, 2020, the Pfizer-BioNTech vaccine has an efficacy rate of upto 95 percent against the disease. The mRNA-type vaccine also requires two doses, taken at a time gap of about 3 weeks between both doses. Common side effects of the Pfizer-BioNTech vaccine include headache, chills, pain, tiredness, redness, and swelling at the injection site. These concerns are resolved within a day or two of proper rest, hydration, and medications. It is required to be stored in a super-cold freezer and can be only used for five days after thawing.

How does an mRNA vaccine work?

A new technology, Messenger RNA (mRNA) is used to manufacture the COVID-19 vaccine. According to Yale Medicine, the Pfizer-BioNTech and Moderna mRNA vaccines deliver a small piece of genetic code from the Sars-CoV-2 virus to host cells in the body, unlike other vaccines that put an inactivated disease germ into the body. These vaccines give instructions to cells to make copies of spike proteins which stimulate an immune response to produce antibodies. It further develops memory cells to recognise and respond to infections in the body.

How does mRNA vaccine work on virus mutations?

In early May 2021, two studies were conducted on the real-world use of the Pfizer-BioNTech vaccine. According to the research, the vaccine provides strong protection against severe disease or death from the Alpha variant (first detected in the UK) and the Beta variant (first identified in South Africa).

Another study conducted by Public Health England showed that after full vaccination (both vaccine doses) is 88 percent effective against symptomatic infection in the case of the Delta variant (first seen in India) and 96 percent effective against hospitalisation.

OXFORD-ASTRAZENECA

Approved by the UAE in January 2021, the Oxford-AstraZeneca vaccine is 85 percent effective in protecting against the disease. It requires two doses to be taken in a time gap of 4-12 weeks between both doses. Common side effects include pain, tenderness, warmth, itching, swelling, redness, or bruising at the injection site. These issues get fixed within a day or two. The vaccine can be easily stored, transported, and handled in normal refrigeration for at least six months.

How does it work?

The vaccine is made from a weakened version of a common cold virus (known as an adenovirus) from chimpanzees. It has been further modified to fight genetic material developed by Coronavirus. After injected into the body, it teaches the immune system how to tackle the virus.

How much is it effective against variants?

According to a study released in February, two doses of the AstraZeneca vaccine have 74.6 percent efficacy against the Alpha variant. But the vaccine is not able to provide enhanced protection from mild and moderate symptoms in case of infection from the Beta variant of Coronavirus. It resulted in the South Africa government deciding to stop the use of the AstraZeneca vaccine and choose Johnson & Johnson and Pfizer-BioNTech vaccines.

For the Delta variant, two recent studies indicated that full vaccination with AstraZeneca doses is 60 percent effective against symptomatic disease and 93 percent effective in case of hospitalisation due to infection.

SPUTNIK V

The UAE approved the Russia-made Sputnik V vaccine with an efficacy rate of 91.4 percent on January 21, 2021. The vaccine requires two doses taken between time gap of 21 days-3 months of both doses. The vaccine can be stored at a temperature of 2 to 8 degrees Celsius.

How does it work?

Sputnik V is based on an adenoviral vector-based platform. Adenovirus is a type of virus associated with common cold and other related illnesses that serves as the delivery vehicle for DNA instructions to produce spike protein of Sars-CoV-2 virus in the body. It further results in production of antibodies against the spike protein to prepare the body's immune system against potential infection.

Furthermore, both doses use different types of adenoviruses - first dose with type-26 (Ad26) and second booster dose with type-5 (Ad5). The objective of using two different types of adenoviruses is to reduce the possibility of body developing antibodies after the first dose, which could make the second dose ineffective. So far, only Sputnik V is using this approach, while others such as the Oxford–AstraZeneca vaccine are using same material for both doses.

How well does the vaccine work against virus mutations?

As per the research paper "Understanding the Covid-19 Variants of Concern", Sputnik V has proven effective against viruses with a spike from the Alpha variant. However, it is less effective against the Beta variant. While vaccine produces have claimed that Sputnik V is around 90 percent effective against the Delta variant, medical journals are yet to publish their results on the matter.

SINOPHARM

The UAE approved the Sinopharm vaccine on December 9, 2020. With an efficacy rate of 86 percent against COVID-19 infection, the vaccine requires two doses taken at a time gap between 21 to 28 days between both doses. Common side effects include illness, headache, fatigue, pain and relative reaction on the injection site. The vaccine can be stored in the original packaging in a refrigerator at +2 to +8 °C.

How does the vaccine work?

The Sinopharm vaccine is made from inactivated Sars-CoV-2 virus that was treated with a chemical called beta-propiolactone. This chemical helps in binding the genetic material of the virus and further stops it from replicating and causing COVID-19 infection.

As the vaccine is injected into the body, the immune system identifies the inactivated virus as foreign and starts producing antibodies against it. If the vaccinated person comes in contact with Sars-CoV-2, their immune system develops an immune response against the virus.

How well does the vaccine respond against variants?

According to the World Health Organisation, the vaccine has not yet been evaluated in response to Coronavirus variants. However, as per the "Understanding of the Covid-19 Variants of Concern" paper, the Sinopharm vaccine creates an immune response against the Beta variant. But there is not much data available on its effectiveness against the other two variants - Alpha and Delta.

Which is the best vaccine?

It is important to note that each COVID-19 vaccine is unique, providing protection against the virus. The best vaccine is the vaccine that you have received as part of the inoculation drive to boost safety for everyone against COVID-19. Medical experts have called on all community members to get vaccinated with the aim of achieving herd immunity. The UAE authorities have assured that all vaccines approved as part of the national vaccination drive are effective at preventing severe infection from Sars-Cov-2.