AAll viruses mutate. They do this to better adapt and survive better in their particular host. The virus that causes Covid-19 is no different: it has moved from the animal kingdom, where it probably originated in bats, to the human world. Since then, scientists have been caught in a battle between the spread of the virus and the ability to immunize against it. We now have the vaccinations to protect us from Covid-19 – but what happens if this virus mutates further, as it probably is?
As restrictions on closure ease, South London has already seen a group of new cases related to the South African variant. Over the next six months, dealing with emerging variants will be one of the biggest challenges facing scientists. Some vaccines show promising signs of handling new variants – the mRNA vaccines manufactured by Pfizer and Moderna seem to offer some protection against the variants first identified in Kent and South Africa. Most virologists believe that Covid-19 vaccines will protect against serious diseases and death, even in people infected by a mutated virus strain.
But there are still potential problems. Getting vaccinated does not necessarily prevent you from becoming asymptomatic with Covid-19 and transmitting the virus. In addition, some vaccines may offer little or no protection against people infected with a Covid-19 variant and transmitted to others (but experts believe that vaccines, coupled with a host’s natural immune response, should still provide adequate protection. offers serious illness and death). For example clinical trials and laboratory studies show that the AstraZeneca vaccine is only about 10% effective in protecting against the South African variant, but scientists still think that the jab will protect against this disease against serious diseases. Another question is how long the vaccine immunity lasts, and whether people become more susceptible to different variants as their antibody levels decrease over time.
Virologists hope the vaccines will trigger long-term anamnestic immunity. In essence, this would mean that a person’s B cells and T cells (possibly lifelong) would remember the specific S proteins of the virus to which they were exposed after being vaccinated. Thus, if the person encounters the virus again, their immune system can respond quickly by producing activated B cells (which produce antibodies) and T cells (which kill virus-infected cells) to fight it.
The virus that causes Covid-19 can produce new variants in at least two different ways. First, the virus can undergo recombination, which happens when different pieces of gene from different viruses infect the same cell and mix to produce new variants. Second, the virus can infect one patient with an immune weakening for a long time and then develop within that patient to produce a new variant. This evolutionary process can lead to the emergence of a new variant that can evade the immune responses of its host, which can offer it certain benefits when it spreads to other people.
How then can we combat new variants when they arise? Some of the first-generation Covid-19 vaccines, such as the mRNA, offer a wider range of protection than others. There are already plans to update the Pfizer, Moderna and AstraZeneca vaccines to better match the South African variant. But it is practically and economically difficult to constantly update every vaccine for Covid-19 every time a new variant appears. Although vaccine redesign has been facilitated by the introduction of ‘vaccine platforms’, there is still a significant lapse of time with the manufacture of new shots and their application to vulnerable populations.
One option is to treat Covid-19 as during seasonal flu. Each year, experts carefully select an updated flu stop based on what they think will become the dominant flu strain. We can apply this head to Covid vaccines to cover as many new variants as possible. This is the goal of the World Health Organization’s network of laboratories in the US, UK, China, Japan and Australia, working together to identify emerging strains of the flu virus.
A global Covid-19 monitoring network can function in the same way. This involves hospital diagnostic laboratories from around the world submitting clinical samples to laboratories that can then compare the different virus sequences from different hemispheres. An observation network will determine how many Covid vaccines need to be designed, manufactured and distributed to focus on emerging variants. Depending on how quickly variants emerge, a new vaccine may be needed annually or every few years.
Of course, there is always a doomsday variant that escapes all existing vaccinations and natural immunity. With flu, it is a very well-known risk: experts call it a “pandemic” strain. Over the coming years, it could also be a risk for the virus that causes Covid-19. Only constant vigilance, monitoring and cooperation will help the world to detect such a variant and prevent a catastrophic pandemic from occurring again.