How does the Sputnik V COVID-19 vaccine work?


The Sputnik V COVID-19 vaccine uses two harmless viruses that deliver the genetic code for our cells to make a protein from the new coronavirus. This trains our immune system to fight against future infections with the new coronavirus.

The Sputnik V vaccine, which also bears the name Gam-COVID-Vac, currently has authorization for use in 68 countries. The Gamaleya National Center of Epidemiology and Microbiology in Moscow, Russia, developed the vaccine.

Sputnik V is a viral vector vaccine designed to produce lasting immunity against COVID-19. According to an interim analysis of phase 3 clinical trial data published in The Lancet, the vaccine’s efficacy is 91.6%Trusted Source.

However, a number of scientists have publicly called into question the results from the phase 1/2Trusted Source and phase 3Trusted Source trials.

What is a viral vector?
A viral vector is a harmless virus that can deliver a gene to our cells that they turn into a protein. Scientists have studied the use of viral vectors for gene therapy and vaccines.

When a viral vector vaccine delivers the genetic code for our cells to make a pathogen’s protein, our immune system reacts to the presence of the protein and the viral vector. This elicits an immune response that can lead to lasting immunity.

The Sputnik V COVID-19 vaccine uses two different adenoviruses as the viral vectors. Adenoviruses are a large family of viruses that can cause the common cold.

In order to train the immune system to recognize the SARS-CoV-2 virus, which causes COVID-19, people receive the vaccine in two doses at an interval of 21 days. The first shot contains adenovirus 26 (Ad26) as the viral vector, while the second shot contains adenovirus 5 (Ad5). Both shots also contain the gene for the SARS-CoV-2 spike protein.

Scientists have chemically modified the adenoviruses in the Sputnik V COVID-19 vaccine to stop them from replicating. This means that the viral vectors cannot cause an adenovirus infection.

The vaccine also cannot cause COVID-19 because it does not contain the entire SARS-CoV-2 virus.

Our immune system reacts to the vaccine by developing antibodies specific to the SARS-CoV-2 virus and by eliciting T-cell responses. In the event of future infection, our bodies can rapidly produce these antibodies to bind to the virus and prevent it from entering our cells.

T-cells can kill infected cells. Both the viral vector and the SARS-CoV-2 spike protein play a role in building up immunity in this way.

Why use two viral vectors?
When our immune system reacts to the presence of a viral vector, we can build up immunity. If we reencounter the same viral vector, our bodies may try to fight against it. This could make a vaccine less effective.

The Sputnik V vaccine aims to sidestep this issue by using two different viral vectors, Ad26 and Ad5.

Yet, there is another point to consider. As adenovirus infections are common, some people already have pre-existing immunity to either or both of these viral vectors.

Indeed pre-existing immunity to Ad5 is widespreadTrusted Source. The impact that this has on vaccination with Ad5-based COVID-19 vaccines is not clear at the moment.

While pre-existing immunity to Ad26Trusted Source does exist, scientists believe that this does not hamper a successful immune response.

Published data from the Sputnik V vaccine clinical trials indicate that the vaccine is safe and effectiveTrusted Source, although questions around data quality remain.

How do COVID-19 vaccines work?
COVID-19 vaccines work by introducing the immune system to an inactivated form of the SARS-CoV-2 coronavirus or a part of it. This does not cause COVID-19 but equips the body to fight against future infection with the virus.

All data and statistics are based on publicly available data at the time of publication. Some information may be out of date. Visit our coronavirus hub and follow our live updates page for the most recent information on the COVID-19 pandemic.

All vaccines work by training the immune system to respond to future infection. Vaccines are overwhelmingly safe for the majority of people who receive them, and they do not cause disease.

There are 12 vaccines against COVID-19 that have authorization for use in various locations around the world.

Vaccine developers worked under unprecedented conditions to develop vaccines against COVID-19 after the emergence of the SARS-CoV-2 virus in late 2019. It took less than a year for the first COVID-19 vaccines to gain authorization for use.

While this is significantly faster than for all other vaccines, developers leveraged existing vaccine technology and a concerted global effort — working alongside health authorities such as the Food and Drug Administration (FDA) — to work at this pace.

In this Special Feature, we take a look at how different COVID-19 vaccines work and what scientists mean when they talk about side effects and vaccine efficacy.

Specifically, we cover:

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

Different vaccine types
Although all of the COVID-19 vaccines in use around the world aim to achieve the same goal — namely, protection from COVID-19 — they employ different vaccine technologies.

Some vaccines are based on the whole SARS-CoV-2 virus, others use only parts of it, and some do not use any material derived directly from the virus.

The sections below provide an overview of the different types of COVID-19 vaccines that have authorization for use in at least one country.

The COVID-19 mRNA vaccines that BioNTech-Pfizer and Moderna developed are the first mRNA vaccines authorized for use in humans outside of clinical trials. However, the technology is not new.

Scientists have been working on mRNA vaccine candidates for infectious diseases and cancer for a number of years.

mRNA vaccines do not contain any part of the SARS-CoV-2 virus. Instead, they carry a chemically synthesized piece of messenger (m)RNA that contains the information necessary for our own cells to make the SARS-CoV-2 spike protein.

Our cells make this protein and present it to our immune system, which responds by creating antibodies and developing longer lasting immunity in the form of T cell and B cell responses.

It is not possible to develop COVID-19 from an mRNA vaccine because it does not carry the instructions necessary to make the entire coronavirus.

Viral vector vaccines
Like mRNA vaccines, viral vector vaccines also do not contain the whole SARS-CoV-2 virus. They use a harmless virus to deliver the gene that allows our cells to make the spike protein.

The Oxford-AstraZeneca, Sputnik V, and Johnson & Johnson COVID-19 vaccines are all viral vector vaccines that use different adenoviruses as the delivery system, or vector. Adenoviruses can cause the common cold, and there are many different types of adenoviruses that can infect different species.

The Oxford-AstraZeneca vaccine uses a chimpanzee adenovirus vector called ChAdOx1. The Russian Sputnik V vaccine uses two different human adenovirus vectors called Ad26 and Ad5. Johnson & Johnson also use the Ad26 virus in their vaccine.

All three vaccines contain the gene for the spike protein and deliver this into cells after injection. The cells then make the spike protein and present it to our immune system.

As with mRNA vaccines, viral vector vaccines do not carry the information necessary for our cells to make the entire SARS-CoV-2 virus. Therefore, they cannot cause COVID-19.

Subunit vaccines
Like mRNA and viral vector vaccines, subunit vaccines only use a part of the SARS-CoV-2 virus. However, rather than providing our cells with the genetic code necessary to make a viral protein, subunit vaccines deliver the protein directly.

The Novavax COVID-19 vaccine candidate is a subunit vaccine. Scientists produced large amounts of the SARS-CoV-2 spike protein in a laboratory for this experimental vaccine. Novavax use insect cells to grow the proteins before purifying them. The purified proteins then form nanoparticles.

On their own, the protein nanoparticles may not produce a strong enough immune reaction, so Novavax add an adjuvant. This is a chemical that stimulates the immune system.

Subunit vaccines do not carry enough viral material to make the whole SARS-CoV-2 virus. Therefore, they cannot cause COVID-19.

Inactivated vaccines
Unlike mRNA, viral vector, and subunit vaccines, inactivated vaccines contain the entire SARS-CoV-2 virus. However, the virus is chemically modified to inactivate it, which means that it cannot cause disease.

Sinovac, Sinopharm, and Bharat Biotech all use a chemical called beta-propiolactone to inactivate the SARS-CoV-2 virus in their vaccines. The chemical modifies the virus’s genetic material.

Inactivated COVID-19 vaccines cannot cause COVID-19, as the virus cannot make copies of itself.

This type of vaccine does not produce as strong an immune reaction as some others, and the resulting immunity may not be as long lasting. Sinovac, Sinopharm, and Bharat Biotech use adjuvants in their COVID-19 vaccines to generate a stronger immune response.

To provide immunity in the long run, it may be necessary to receive booster shots after receiving an inactivated COVID-19 vaccine.

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