Coronavirus vaccine tracker
A look at the different vaccines under development, and where they are in the pipeline
The Canadian government has given approval to Pfizer/BioNTech and Moderna's COVID-19 vaccines. The approval under the interim order is an important step to start a mass immunization program.
An effective vaccine against the coronavirus that causes COVID-19 is everyone's hope for a real return to normal life.
Human trial results released this fall showed several vaccines to be highly effective at preventing COVID-19. Meanwhile, Canada has already preordered hundreds of millions of doses of vaccines under development from several different manufacturers.
More than 100 teams of scientists around the world have been working to develop and test a vaccine against the virus SARS-CoV-2 as quickly as possible. They're employing a huge variety of strategies and technologies, including some that have never been used in an approved vaccine before.
"It's a very fascinating and kind of impressive effort," said Dr. Lynora Saxinger, an infectious disease specialist at the University of Alberta in Edmonton.
"It's absolutely crucial."
Even in countries that have had a devastating number of deaths from COVID-19, there is nowhere close to a level of "herd immunity" within the population preventing the disease from spreading exponentially if we go back to normal levels of social interaction, she said.
How does a vaccine go from development to approval?
Typically, it takes an average of more than 10 years for a vaccine to get from pre-clinical development (including animal testing) through three phases of clinical (human) trials to market registration.
The process has been fast-tracked for COVID-19. The first human vaccine trials began in March, just two months after the virus and disease were identified. And different phases of human trials are being run in an overlapping fashion instead of one at a time — for example, Phase 2 might begin just a few weeks after the start of a six-month Phase 1 trial.
Still, officials, including the World Health Organization, have reassured the public that no steps will be skipped. That’s why Russia drew fierce criticism when it announced in mid-August that it was granting regulatory approval to a vaccine developed by Gamaleya Research Institute of Epidemiology after less than two months of human testing, with only two incomplete Phase 1 trials registered with the WHO. (Russia later said the approval was a "conditional registration certificate" that requires additional clinical trials.)
It's up to each country's regulators to review trial results and approve a vaccine for use or not. A vaccine may get emergency use authorization before receiving formal approval. Canada's approval under the interim order means a mass immunization program can begin before full aprroval is granted.
Candidate vaccines in clinical trials
Multiple vaccines on the horizon?
Most vaccine candidates that make it to preclinical testing never make it to market (about 94 per cent fail, a 2013 study found). But in this case, with so many different vaccines under development, there may still end up being multiple vaccines for the coronavirus, possibly using different strategies, Saxinger predicts.
There are a number of potential advantages if that happens:
- They'd be using different ingredients and manufacturing facilities and wouldn't be competing for resources — allowing for more vaccine production.
- Different vaccines have different pros and cons. Some vaccines require more doses to be effective than others, while ease of manufacturing, testing and distribution varies.
- Some vaccines may be more suitable for some populations than others, due to factors such as age or genetics.
Stephen Barr is associate professor of microbiology and immunology who is part of a COVID-19 vaccine development team at Western University in London, Ont. He noted that the "best" vaccine in the end may not be best for everybody. "But the second one might be, for those that don't respond, right? So it's always good to have these backup vaccines as well or vaccines that can be used in parallel around the world."
Many teams are working on a COVID-19 vaccine using technologies that have been in development for decades but have never yet been approved for wide-scale human use, such as DNA, RNA and non-replicating viral-vector vaccines. Many of those candidates are considered very promising, garnering huge amounts of funding and billions of preorders from some countries. One has even already received emergency approval in the U.K.
Since August, Canada has announced deals to reserve hundreds of millions of doses of vaccines from Moderna/NIAID, BioNTech/Fosun Pharma/Pfizer, Janssen Pharmaceutical Companies (Johnson & Johnson), Novavax, Sanofi and University of Oxford/AstraZeneca.
Whole virus vaccines
These are the most traditional types of vaccine. They've been used for a long time, and most of us have had these kinds of vaccines.
In this case, the virus is grown in large quantities in cells, and then killed, often with a chemical, which is usually formaldehyde, but heat or radiation can also be used. Two kinds of flu vaccines are made this way, grown in either chicken eggs or mammalian cells.
- Unlike live virus vaccines, it can even be given to people with weakened immune systems.
- It may not lead to as strong an immune response as a live virus. Several doses, including boosters at regular intervals, are usually necessary.
- It requires the virus to be grown in large quantities and that can take time and may not be as easy to scale up as other kinds of vaccines.
Live, attenuated virus
In this case, viruses are also grown in cells, but instead of being killed they're genetically "weakened" so they can't infect cells and reproduce as effectively. Traditionally, this was done by getting the virus to grow in and adapt to an environment different than the one they normally infect. That's the approach used for vaccines such as varicella (chicken pox) or yellow fever. The SARS-CoV-2 vaccine candidates of this type use a high-tech genetic engineering approach called "codon deoptimization," where the virus is rebuilt from scratch, incorporating targeted mutations that weaken it.
- Similar to real infection and usually provides long-lasting protection — sometimes lifelong — after one dose.
- May not be suitable for people with weakened immune systems, long-term health problems, or people who've had organ transplants.
- Live viruses need to be refrigerated, making them more difficult to transport and unusable in countries without access to refrigeration.
- The virus must be grown in large quantities. That can take time and it may not be easy to scale up.
Vaccines that target part of a virus
These types of vaccines don't contain entire viruses. They present parts of viruses, such as proteins, to your immune system to help it learn to recognize the virus and build an immune response.
In the case of SARS-CoV-2, the part of the virus that's typically targeted is the spike or "S" protein — the projections on its outer coat that make it look like a crown under a microscope ("corona" means "crown.") That's the protein the virus uses to bind to human cells, allowing it to enter them.
What varies among different vaccine candidates is the way they make the spike protein and get it into the body — it may be injected directly; manufactured by the human body itself using instructions encoded in DNA or RNA; or a "carrier virus" called a viral vector may bring those instructions and/or the spike protein itself into the body.
Virus-like particles (VLPs) are a special type of protein subunit vaccines — vaccines where the protein is made outside the body and then used as a vaccine. With VLPs, the proteins self-assemble into particles that are intended to look like viruses to the human immune system.
Some vaccines on the market that use VLPs include vaccines for HPV (human papilloma virus) and Hepatitis B.
- May produce a stronger immune response than regular subunit vaccines.
- Production may be much faster than for whole virus vaccines.
- Ensuring stability and purification can add to production time.
- Can be hard to produce in large quantities.
With RNA vaccines, what's injected into the body is simply the genetic instructions to make a viral protein such as the spike protein. Cells in your body then use the instructions to make the protein inside the body for your immune cells to see and respond to.
- No virus is needed to make the vaccine, which may cut production time compared to conventional vaccines.
- Not stable and needs to be stored at very cold temperatures.
This is very similar to the RNA vaccines, except that DNA is used instead of RNA. It's often delivered as a ring of DNA called a plasmid.
That enters the cell, and the cell produces the virus protein.
- Quick and relatively inexpensive to manufacture in large quantities.
- Shelf stable and doesn't require freezing in storage and transport.
- Needs to get into the nucleus, which is more challenging than RNA.
As previously mentioned, with this type of vaccine, the protein is made outside the body. Traditionally, this was done by breaking whole viruses into pieces using detergent or a solvent such as ether.
However, this can now be done with "recombinant" genetic technology, where the gene for a protein is inserted into another organism to grow the protein in large quantities.
- Can be produced more quickly than live vaccines.
- May not generate as strong an immune response as whole virus vaccines.
An additional compound called an adjuvant may need to be to be included to boost a patient's immune response.
- May not be scaled up as quickly as production of RNA or DNA vaccines.
Lots of Canadian candidates
As mentioned earlier, Canada currently has at least eleven vaccine candidates under development, with Canadian involvement in the development of some others. Saxinger said that maximizes the impact of the expertise we have, from work on diseases such as Ebola, SARS and MERS.
All are behind the global frontrunners in development, but the most advanced, Medicago’s, has been preordered by the federal government.
Michael Houghton, the University of Alberta professor leading that university’s vaccine development team, says some of the COVID-19 vaccines under development in Canada may be useful as boosters later on, as they may be cheaper than the earliest COVID-19 vaccines approved.