How the COVID19 Vaccines Work

If you're curious (like I am) about how the current likely COVID19 vaccines work, their similarities and differences and which is the most viable for the general public, this blog will help explain them. 

. On Nov. 24, Huffpost provided an overview of  4 vaccines and how they work. Science News explained about the Moderna vaccine. So, I put them together with links to each source. 

   Since the Pfizer vaccine requires storage at extreme cold temperatures (which are more difficult to provide everywhere), I read that it would likely be given to healthcare workers where facilities can accommodate those environmental conditions. Here's the breakdown from Huff PostUK and Science News):

1) BioNTech/Pfizer 

This vaccine is called an mRNA vaccine – it uses a bit of the coronavirus’ genetic code to prompt the body to initiate an immune response.

While many standard vaccines work by injecting a dead or weakened form of a virus into the body in order to build immunity, RNA vaccines introduce a messenger RNA (mRNA) sequence into the body that contains the genetic instructions for the vaccinated person’s own cells to produce the vaccine antigens and generate an immune response.

It’s a bit like injecting an instruction manual so your body is able to build a bit of the virus protein, which then prompts an immune response. The body then knows how to fight the virus if you come into contact with it in real life. 

(Science News said: "the pharmaceutical giant faces a huge challenge in distributing its vaccine, which has to be kept an ultrafrosty –70° Celsius, requiring special storage freezers and shipping containers. That means that even though the vaccine developed by Pfizer and its German partner BioNTech is likely to be the first vaccine to reach the finish line in the United States, its adoption may ultimately be limited. ")

Analysis of phase 3 trials has found it to be 95% effective against Covid-19, beginning 28 days after the first dose. To date, the Data Monitoring Committee for the study has not reported any serious safety concerns. 

2) Moderna 

Science News reported: A similar vaccine developed by Moderna and the U.S. National Institute of Allergy and Infectious Diseases also requires freezing. But it survives at a balmier –20° Celsius, so can be kept in a standard freezer, and can even be stored at refrigerator temperatures for up to a month.. Most vaccines don’t require freezing at all, but both Pfizer and Moderna’s vaccines are a new type of vaccine for which the low temperatures are necessary to keep the vaccines from breaking down and becoming useless.

Both Biotech/Pfizer and Moderna vaccines are based on messenger RNA, or mRNA, which carries instructions for building copies of the coronavirus’ spike protein. Human cells read those instructions and produce copies of the protein, which, in turn prime the immune system to attack the coronavirus should it come calling.  

3) University of Oxford/AstraZeneca 

This vaccine harnesses an adenovirus (common cold virus) from chimpanzees, which has been genetically modified so it can’t replicate in our body’s cells. This virus is used as it contains the genetic material of the SARS-CoV-2 virus spike protein (a protein that lives on the surface of the coronavirus).

When the vaccine enters cells inside the body, it uses this genetic code to produce the surface spike protein of the coronavirus, priming the immune system to attack the SARS-CoV-2 virus if it later infects the body.

(Image right: Source: GAVI, the Vaccine Alliance)

Analysis of phase 3 trials has found it to be 70.4% effective when combining data from two dosing regimens. In two different dose regimens, vaccine efficacy was 90% in one and 62% in the other. The more effective regimen used a halved first dose and standard second dose. No serious safety events related to the vaccine were identified.

Professor Andrew Pollard, director of the Oxford Vaccine Group and chief investigator of the Oxford Vaccine Trial, said: “Excitingly, we’ve found that one of our dosing regimens may be around 90% effective and if this dosing regimen is used, more people could be vaccinated with planned vaccine supply.”

4) Janssen 

The vaccine is an adenoviral vaccine, so it’s very similar to the University of Oxford/Astrazeneca vaccine in terms of how it works. However it’s different in that the adenovirus used is from humans (rather than chimpanzees). The virus has also been modified, so it can’t multiply in the body or cause illness.

This vaccine is currently in phase 3 trials.

5) Novavax 

The Novavax vaccine uses a slightly different technology to the others – it is engineered from the genetic sequence of SARS-CoV-2. The company’s technology turns insect cells into factories for the coronavirus spike protein and the vaccine combines several of the spike proteins in a nanoparticle.

It also contains something called an adjuvant, which is used in other vaccines to enhance the immune response and stimulate high levels of neutralising antibodies. The UK already provides an adjuvanted flu vaccine to the over-65s, so we know this technology is safe and works.

This vaccine is currently in phase 3 trials.