Coronavirus disease 2019 (COVID-19) is a highly contagious respiratory illness caused by the SARS-CoV-2 virus. The virus was first identified in December 2019 in Wuhan, China, and has since spread rapidly around the world, causing a global pandemic. As of the time of writing, the virus has infected over 400 million people and has caused over 6 million deaths worldwide.

SARS-CoV-2 Variants:

Like all viruses, SARS-CoV-2 can mutate over time, leading to the emergence of new variants. Some of these variants have shown to be more transmissible, more virulent, and more resistant to existing vaccines and treatments.

Here are some of the notable SARS-CoV-2 variants:

1. Alpha variant (B.1.1.7):

first identified in the UK in December 2020, the alpha variant is estimated to be 50-70% more transmissible than the original strain.

2. Beta variant (B.1.351):

first identified in South Africa in December 2020, the beta variant has mutations that make it more resistant to some existing vaccines.

3. Gamma variant (P.1):

first identified in Brazil in January 2021, the gamma variant is also more transmissible and has mutations that may help it evade the immune system.

4. Delta variant (B.1.617.2):

first identified in India in December 2020, the delta variant is now the dominant strain in many countries and is estimated to be 50-60% more transmissible than the alpha variant.

Types of COVID-19 Vaccines:

Several vaccines have been developed and authorized for use against COVID-19. These vaccines work by training the immune system to recognize and fight the virus.

Here are the main types of COVID-19 vaccines:

1. mRNA vaccines:

Pfizer-BioNTech and Moderna vaccines are mRNA vaccines. They contain a small piece of genetic material called messenger RNA (mRNA) that instructs cells to make a protein found on the surface of the SARS-CoV-2 virus. The immune system recognizes this protein as foreign and mounts an immune response against it.

2. Vector vaccines:

AstraZeneca and Johnson & Johnson vaccines are vector vaccines. They use a harmless virus, such as adenovirus, to carry genetic instructions into cells to produce a protein found on the surface of the SARS-CoV-2 virus, triggering an immune response.

3. Protein subunit vaccines:

Novavax vaccine is a protein subunit vaccine. It contains harmless pieces of the SARS-CoV-2 virus, which trigger an immune response.

4. Inactivated or killed virus vaccines:

Sinovac and Bharat Biotech vaccines are inactivated or killed virus vaccines. They contain a virus that has been killed or inactivated, which can no longer cause disease but can still trigger an immune response.


COVID-19 remains a global health crisis, and it is essential to stay vigilant and continue following public health guidelines, such as wearing masks, practicing social distancing, and washing hands frequently. Vaccination remains one of the most effective ways to prevent severe disease and hospitalization from COVID-19. However, the emergence of new variants highlights the need for ongoing research and development of new vaccines and treatments to stay ahead of the virus.

hamzah 16/01/2024 - 09:59

Pas encore de commentaire



This site uses necessary cookies to streamline its operations, remembering connection data, chosen language, and message validation.