How do COVID-19 vaccines work?

COVID-19 vaccines introduce the immune system to an inactivated SARS-CoV-2 virus or a portion thereof. This vaccine does not cause COVID-19, but it equips the body with the ability to fight off future infections.

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Vaccines are design to train the immune system to fight future infections. Vaccines are highly safe and do not cause any disease in most patients who have them.

The 12 vaccinations against COVID-19 are authoriz for use in different locations around the globe.

After the SARS-CoV-2 outbreak in late 2019, vaccine developers had to work under extreme conditions to create vaccines against COVID-19. The first COVID-19 vaccines were approve for use in less than one year.

It is significantly faster than any other vaccine. However, the developers used existing vaccine technology and a coordinated global effort to work at this speed.

This Special Feature examines the different COVID-19 vaccines and what scientists mean by side effects and vaccine efficacy.

We cover:

  • mRNA vaccines
  • viral vector vaccines
  • subunit vaccines
  • inactivated vaccines
  • vaccine side effects
  • vaccine efficacy

Different vaccine types

All COVID-19 vaccines are designe to protect against COVID-19, but they use different vaccine technologies.

Some vaccines use the entire SARS-CoV-2 virus, while others only use parts. Others do not use any material directly from the virus.

These sections provide an overview of COVID-19-approved vaccines for at least one country.

mRNA vaccines

Moderna and BioNTech-Pfizer developed the COVID-19 vaccines, the first mRNA vaccinations approved for human use outside of clinical trials. The technology isn’t new.

For many years, scientists have been researching mRNA vaccine candidates to treat infectious diseases and carcinoma.

The mRNA vaccines don’t contain any of the SARS/CoV-2 viruses. They have a chemically synthesized mRNA (messenger) that includes the necessary information for our cells to produce the SARS-CoV-2 spike proteins.

This protein is made by our cells and presente to our immune system. The immune system responds by creating antibodies and developing a longer-lasting immunity in T and B cell responses.

Because the mRNA vaccine does not contain the necessary instructions to make the whole coronavirus, it is impossible to create COVID-19.

Viral vector vaccines

Viral vector vaccines do not contain the entire SARS-CoV-2 virus, just like mRNA vaccines. They use a benign virus to deliver the gene which allows our cells to make the spike protein.

Sputnik V and Oxford-AstraZeneca vaccines and Johnson & Johnson COVID-19 use different adenoviruses to deliver their vaccines. Adenoviruses can cause common colds. There are many types of adenoviruses.

The Oxford-AstraZeneca vaccination uses a ChAdOx1 chimpanzee virus vector. Russian Sputnik V vaccine employs two different human Adenovirus vectors, Ad26 and Ad5. Johnson & Johnson uses the Ad26 virus for its vaccine.

The vaccines all contain the gene for the spike proteins and are delivere to the cells by injection. The cells make the spike protein, which is then present to the immune system.

Like mRNA and viral vector vaccines, they do not contain the necessary information for our cells to make the whole SARS-CoV-2 virus. They cannot, therefore, cause COVID-19.

Subunit vaccines

Subunit vaccines are similar to mRNA or viral vector vaccines. They only use a portion of the SARS/CoV-2 virus. Subunit vaccines, however, deliver the protein directly to our cells instead of providing the genetic code required for making a virus protein.

Novavax COVID-19 is a subunit vaccine. For this experimental vaccine, scientists produced large quantities of the SARS-2 spike protein in a laboratory.

Novavax uses insect cells to produce the proteins and then purify them. Nanoparticles are form from purified proteins.

Novavax has an adjuvant. The protein nanoparticles on their own may not be strong enough to produce an immune response. This chemical stimulates the immune system.

Subunit vaccines don’t contain enough virus material to cause the entire SARS-CoV-2 virus. They cannot, therefore, cause COVID-19.

Inactivated vaccines

Inactivated vaccines contain all the SARS-CoV-2 virus, unlike mRNA, viral vector, and subunit vaccines. The virus has been chemically destroy to prevent it from causing disease.

Bharat Biotech, Sinopharm, and Sinovac all use a beta-propiolactone chemical in their vaccines to kill the SARS-CoV-2 viruses. This chemical alters the virus’ genetic material.

COVID-19 cannot be caused by inactiva COVID-19 vaccinations since the virus can’t make copies of its self.

This vaccine may not cause as strong an immune response as other types, so the immunity that results may not last as long. Sinovac, Sinopharm, and Bharat Biotech use adjuvants with their COVID-19 vaccines to generate a more robust immune response.

It may be necessary to get booster shots after receiving the inactivated COVID-19 vaccination to maintain immunity.

Side effects and efficacy

Preclinical and clinical studies are conduct on all experimental vaccines. These tests are intend to evaluate the safety of the vaccine and its ability to prevent disease.

Scientists determine the safety of a candidate vaccine by monitoring side effects in trial participants.

They can assess how safe a candidate vaccine is by comparing side effects from experimental vaccines with those who received them.

They can also gather data about the possibility that side effects may occur for people who have received the vaccine.

84.7%Trusted source people who were vaccinated with the Pfizer BioNTech COVID-19 vaccine in clinical trials experienced at least one side effect at the injection site.

The pain was the most common side effect, with 83.1% reporting it among participants between 18 and 55 years old and 71.1% among those over 55 years.

Scientists also test the effectiveness of experimental vaccines in clinical trials. It is done by comparing the number of people who develop the disease in the treatment group with the placebo group.

It refers to vaccine efficacy and describes the percentage of disease that was reduced in a clinical trial.

Researchers reported that 94.1% was influential in the Moderna COVID-19 vaccination.

Vaccine efficacy and vaccine effectiveness are two different things.

 Vaccine efficacy refers to the effectiveness of a vaccine in real-life settings, not just clinical trials. While scientists will continue to investigate the effectiveness of COVID-19 vaccines in community settings, it will be some time before reliable data are available.

Early reports from Israel indicate that the rate for new COVID-19 cases among healthcare workers in Israel who had received the Pfizer BioNTech vaccine was 85Trusted Source lower 15-28 days following the initial injection.

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