Enormous resources are now being put into developing and testing various vaccines against the covid-19 virus.

Since no vaccine against a coronavirus has previously been approved it is not known what type of vaccine will be most effective. The fact that companies and research scientists are focussing on different types of vaccine is therefore beneficial.  

New technology

Although the research groups are using different technologies, the purpose of the vaccine remains the same: to enable the immune system to fight infection.

Many of the covid-19 vaccine candidates are based on the spike protein (S protein) on the surface of the coronavirus SARS-CoV-2. This S protein is important for the virus to initiate infection. The S-protein is used to attach and enter cells, which will then produce more virus. Upon vaccination, the body produces antibodies to the S protein. Neutralising antibodies prevent the virus from binding and entering cells.​

Since we are developing vaccines against a new virus and, in some cases, using completely new vaccine technologies, it is essential that the vaccines are tested thoroughly. The clinical studies must show whether the vaccines really do protect against disease and whether protection lasts for a reasonable period of time. We must also monitor whether any unacceptable side effects occur.  

Some of the vaccines use known technology

Vaccines with inactivated virus 

The vaccine consists of killed covid-19 virus. The killed virus in the vaccine does not cause disease, but the body is stimulated to produce antibodies that can fight the virus if the person subsequently becomes infected. 
This technology is also used in the polio vaccine and some influenza vaccines. 

Vaccine candidates in Phase 3 studies which use inactivated virus: 
  • Covid-19 Vaccine (Vero Cell) Inactivated, Sinovac  (China and others) The authorisation process is underway in the EU.
  • Sinopharm (Beijing) 
  • Sinopharm (Wuhan) 
  • Bharat (India) 
  • Institute of Medical Biology / Chinese Academy of Medical Sciences 
  • Research Institute for Biological Safety Problems (Kazakhstan)  

Vaccines which contain parts of the virus (subunit vaccines) 

The vaccine contains specific pieces of the covid-19 virus, for example the spike protein or parts of the spike protein. These pieces of the virus do not cause disease, but the body is stimulated to produce antibodies that can fight the virus if the person subsequently becomes infected. 
This technology is also used in the vaccine against hepatitis B and some influenza vaccines. 

Vaccine candidates in Phase 3 studies which use subunit technology: 
  • Novavax (US). The authorisation process is underway in the EU. 
  • Anhui Zhifei Longcom (China) 
  • Clover Biopharmaceuticals / GSK / Dynavax 
  • Medigen / Dynavax / NIAID (US) 
  • Covaxx / United Biomedical  

Virus-like particles (VLP) 

The vaccine contains viral proteins which are aggregated to resemble a virus but cannot multiply. Different cells can be used to produce this type of vaccine. The particles do not cause disease, but the body is stimulated to produce antibodies to fight the virus if the person subsequently becomes infected. 
This technology is also used in the vaccine against HPV (human papilloma virus). 

Vaccine candidates in Phase 3 studies which use virus-like particles: 
  • Medicago (Canada) 

Viral vector - non-replicating 

These vaccines do not contain covid-19 virus, but consist of another virus which acts as a vector to carry the gene coding for the covid-19 virus spike protein. Non-replicating virus vectors cannot replicate in the body. The vaccines that are currently undergoing Phase 3 trials use the common cold virus of the adenovirus family as a vector.   

When the virus (vector) enters the body's cells, the cells will use the information encoded in the gene to produce the spike protein from the covid-19 virus. 

The spike protein does not cause disease, but the body will produce antibodies to the spike protein and also prepare defence cells (T-lymphocytes) to fight the covid-19 virus if the person subsequently becomes infected by it. 

Virus vectors used in these vaccines are defined as gene modified organisms (GMO). Research over many years has not provided any indication that vaccines based on genetically modified organisms (GMO) can result in changes in the vaccinated person’s genetic material. As for all other vaccines, these are only temporarily present in the body before they are broken down and  eliminated.  
This technology is also used in an Ebola vaccine. 

Approved vaccine candidates which use a non-replicating virus vector technology: 
Vaccine candidates in Phase 3 studies which use a non-replicating virus vector technology : 
  • Sputnik (Russia). The authorisation process is underway in the EU. 
  • CanSino (Kina) 

Vaccine technologies which have not previously been used 

mRNA vaccines 

These vaccines represent a new technology. They consist of mRNA, which contains the formula for the spike protein on the covid-19 virus. The mRNA is "wrapped in" small fat particles which help the mRNA to enter the body’s cells. The body’s cells use the formula to produce the spike protein on the covid-19 virus. The spike does not cause disease, but the body will produce antibodies to the spike protein and prepare defence cells (T-lymphocytes) to fight the covid-19 virus if the person subsequently becomes infected by it. 

Approved vaccine candidates which use mRNA technology:

Vaccine candidates in Phase 3 studies which use m-RNA technology: 
  • CureVac (Germany / US). The authorisation process is underway in the EU

DNA vaccines 

These vaccines contain DNA (*) which encodes the spike protein on the covid-19 virus. The body’s cells use the information in the DNA to produce the spike protein on the covid-19 virus. The spike protein does not cause disease, but the body will produce antibodies to the spike protein and prepare defence cells (T-lymphocytes) to fight the covid-19 virus if the person subsequently becomes infected by it.  

(*) The covid-19 virus (SARS-CoV-2) is an RNA virus. The DNA which is used in the vaccine is cDNA (complementary DNA). 

This type of vaccine has never previously been authorised for use against infections in humans. 

Vaccine candidates in Phase 3 studies which use DNA technology: 
  • Inovio Pharmaceuticals (US) / Int. Vaccine Institute / Advaccine (China) 
  • AnGes / Takara Bio / Osaka University (Japan) 
  • Zydus Cadila (India) 

Oppdatert: 16.07.2021

Publisert: 17.12.2020

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