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Variants of the virus that cause COVID-19 are emerging and becoming dominant around the world. For this reason, some vaccines are being updated to allow our immune system to learn to deal with them.
But this process of identifying and characterizing variants that can escape our immune system, and then adjusting a vaccine to deal with them, can take time.
So researchers are designing a universal vaccine against the coronavirus. This could mean a vaccine to protect against different variants of SARS-CoV-2, the coronavirus that causes COVID-19. Alternatively, a universal vaccine would target many different coronaviruses, perhaps one waiting behind the scenes to cause the next pandemic.
This is where the science stands and the challenges ahead.
Why would we need a universal coronavirus vaccine?
Coronaviruses, like SARS-CoV-2, belong to a large and diverse family of viruses that infect humans and animals. And a universal coronavirus vaccine could be particularly important in two scenarios.
The first is the appearance of new variants of SARS-CoV-2. The second is the appearance of new coronaviruses that can cause a pandemic in the future. In fact, SARS-CoV-2 is not the first of the coronaviruses to be “crossed” from animals and can cause serious illness in humans and is unlikely to be the last.
Read more: UN report says humans could contract up to 850,000 animal viruses, unless we protect nature
How do we start?
Researchers are already designing and testing a universal flu vaccine. If successful, this would avoid the need to modify the vaccine every year to protect against new variants. So that we can apply what we have learned to design a universal vaccine against coronavirus.
Read more: A universal flu vaccine can be one step closer, providing lasting protection against flu
We could look for common characteristics
We could identify parts of the virus common to the entire coronavirus family or variants. So we could analyze and compare the genetic sequences of viruses to find some common ground.
Alternatively, we could isolate immune cells that can react with all coronaviruses or with a number of variants. These could be antibodies or T cells (a type of immune cell that specializes in identifying and killing virus-infected cells). Then we could map where in the viruses these viruses are targeting. In other words, we are looking for a common antigen or group of antigens.
We can then use that knowledge to design a vaccine that teaches the immune system how to specifically recognize those parts of the virus.
Several pharmaceutical companies around the world are investigating these approaches against COVID-19, although all are in very early stages of development and clinical trials have not yet begun.
Read more: Explainer: what is the immune system?
We could make a ‘mosaic’ vaccine
An alternative approach is to make a “mosaic” vaccine. This is a vaccine that contains antigens from a few different variants or coronaviruses.
These are arranged in a nanoparticle, an extremely small biological structure made of proteins that serves as a platform for the release of antigens. With this approach, our immune system discovers the commonalities. Then learn how to generate antibodies that react broadly to all the different viruses.
Scientists in the US have tested this method in mice. After being vaccinated with the mosaic vaccine, the mice had an immune response against SARS-CoV-2 and a variety of other bat coronaviruses. The results are interesting for two reasons.
The first is the type of immune response. The mice produced a wide range of neutralizing antibodies, the types of antibodies that can prevent a virus from infecting our cells and therefore provide the strongest protection. These neutralizing antibodies are the main target of vaccines.
The mice also developed an immune response to bat coronaviruses. This strategy could be useful in providing protection against future pandemics, should a bat coronavirus cross over to infect humans.
But “mosaic” vaccines against coronaviruses have yet to be tested in humans.
So what are the challenges ahead?
Designing a universal vaccine against any group of viruses is not an easy task. In fact, universal vaccines against HIV or influenza have been the subject of intense research for years.
Some universal HIV or influenza vaccine candidates have been evaluated in human clinical trials and shown to be safe. However, the efficacy results have generally been modest.
A big challenge is that these vaccines must be able to protect against an incredibly large number of possible variants. The good news is that SARS-CoV-2 mutates more slowly than HIV or influenza viruses, so variants can take longer to appear.
The second challenge is establishing long-lasting immunity, which universal HIV and influenza vaccines have yet to demonstrate.
A third barrier to overcome is learning to anticipate the next virus mutation or which animal coronavirus may cause the next pandemic.
Therefore, it is likely to be a universal coronavirus vaccine, whether its goal is to cover multiple variants of SARS-CoV-2 or animal coronaviruses with pandemic potential, it can take years to develop.
For now, we have to rely on the reformulation of currently available SARS-CoV-2 vaccines to accommodate the emergence of new variants.
Read more: Why We Will Receive COVID Booster Vaccines Quickly and How We Know They Are Safe
