Types of coronavirus vaccines in development

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The body’s natural immune response

Once infected by the coronavirus, our bodies react and try to fight off the virus, often making us very sick in the process. Without a vaccine, here’s how our natural immune response plays out:

The virus commonly enters the human body through the eyes, nose or mouth.

When the body recognizes the virus as a foreign object, an immune cell engulfs and traps the virus so it cannot do harm to the body.

The engulfing cell is known as an Antigen Presenting Cell (APC) because it displays the viral protein known as the antigen after engulfing the virus.

The display activates T cells which examine the antigen and alert B cells of the intruder.

Both immune cells multiply and some of the copies, known as memory cells, will form the basis of the body’s long-term immunity to the coronavirus.

Some of the copied cells get to work immediately. B cells start making antibodies that match the antigen presented by the APC.

The antibodies latch onto the virus to prevent it from entering cells and making more copies of itself.

This whole process is the body’s primary immune response to the coronavirus. But it can take time for the immune system to recognize the intruder and stop it from multiplying.

In the meantime, the body may undergo painful symptoms like fever, cough and difficulty breathing. Vaccines allow humans to build immunity without experiencing illness.

Six approaches to a vaccine

A vaccine’s job is to train the body to generate a protective immune response. A vaccine introduces a version of the virus to the body that is less harmful and won’t cause severe symptoms.

These are the six main types of vaccines in the works to build immunity against the coronavirus.

1. Live attenuated virus

A live attenuated virus is constructed by mutating the original virus.

The mutation creates a weaker virus that cannot cause significant harm to the body.

2. Inactivated virus

An inactivated vaccine is produced by disabling a virus through radiation, chemicals or heat.

The inactive virus cannot cause disease because it is not trying to enter cells and replicate.

3. Protein subunit

A protein subunit vaccine contains a piece – or subunit – of a coronavirus antigen.

It contains no other part of the coronavirus, so it can’t replicate and cause harm.

4. Virus-like particles

Virus-like particle vaccines closely resemble the coronavirus in structure but contain none of its genetic material.

It’s like an empty shell that looks like the coronavirus but isn’t capable of doing damage to the body.

5. DNA and RNA vaccines

DNA and RNA vaccines consist of Messenger RNA (mRNA) or DNA code for making a version of a coronavirus protein.

The code is inserted into a human cell which then uses the genetic instructions to make this antigen. The immune system can then produce antibodies that will recognize that antigen and fight off the virus.

6. Viral vector

Like DNA and RNA vaccines, viral vector vaccines contain instructions for making a coronavirus antigen.

The instructions are carried into a human cell by a harmless virus like the adenovirus which causes the common cold.

These six vaccine types vary in method, but they all introduce an antigen into the body that the immune system can use to build antibodies against the real coronavirus.

Long road ahead

There are more than 240 vaccine candidates worldwide in various stages of development as of Sept. 21, according to the Vaccine Centre at the London School of Hygiene and Tropical Medicine. Around 40 or so have advanced to clinical trials, a stage where the vaccines are tested on people – and where most vaccines wash out.

COVID-19 vaccine candidates

Drug companies and researchers have to jump through many hoops to prove that their vaccines are safe and effective on people. Historically, only 6% of vaccine candidates end up making it to market, often after a years- or decades-long process.

Here is how vaccine development usually works.

pre-clinical

Animal trial

~2 years

Clinical trials

Phase 1

Safety trial

~2 years

Phase 2

Larger group trial

~2 to 3 years

Phase 3

Efficacy trial

~5 to 10 years

approval

Regulators approve

~2 years

production

pre-clinical

Animal trial

~2 years

Clinical trials

Phase 1

Safety trial

~2 years

Phase 2

Larger group trial

~2 to 3 years

Phase 3

Efficacy trial

~5 to 10 years

approval

Regulators approve

~2 years

production

Clinical trials

Phase 1

pre-clinical

Phase 2

Phase 3

approval

production

Regulators aprove

Animal trial

Safety trial

Large group trial

Efficacy trial

~2 years

~2 years

~2 years

~2 to 3 years

~5 to 10 years

Clinical trials

pre-clinical

Phase 1

Phase 2

Phase 3

approval

production

Animal trial

Efficacy trial

Safety trial

Large group trial

Regulators aprove

~2 years

~2 years

~2 to 3 years

~5 to 10 years

~2 years

The global race for a COVID-19 vaccine is shattering the norms of speed and safety in drug and vaccine development. Through a White House initiative dubbed Operation Warp Speed, the United States is aiming to deliver 300 million doses of a COVID-19 vaccine by January 2021.

Typical development timeline

10-15

YEARS

Operation Warp Speed

~1YEAR

Typical development timeline

10-15

YEARS

Operation Warp Speed

~1YEAR

Typical development timeline

10-15

YEARS

Operation Warp Speed

~1YEAR

Typical development timeline

10-15

YEARS

Operation Warp Speed

~1YEAR

To save time, some developers are combining different phases of the clinical trials or running them at the same time, and some regulatory review is being fast-tracked. Others are working with regulators in multiple countries simultaneously, looking for the quickest path to market.

Experts have warned that the political pressure to speed the approval process at the potential expense of safety is leading to concerns.

Even once there is a working vaccine, that doesn’t mean the pandemic is over. Emerging evidence suggests that the body’s immune defence against COVID-19 may be short-lived, meaning vaccines may not be able to fully protect people in future waves of infection, scientists say.

“The over-reliance on a vaccine (to control the pandemic) is not wise,” said Stephen Griffin, a Leeds University associate professor of medicine.

Sources

World Health Organization; Centers for Disease Control and Prevention; Vaccine Centre at the London School of Hygiene and Tropical Medicine; International Federation of Pharmaceutical Manufacturers and Associations; Reuters reporting

Additional reporting by

Christine Soares

Edited by

Christine Chan and Will Dunham