The coronavirus juggernaut continues to travel across the globe. For now we are relying on tools such as physical distancing to control the spread of the virus, but in the long term a Covid-19 vaccine may be our best hope for a return to normal life.
Yet there have been contradictory reports about how soon a useable vaccine might emerge. The World Health Organisation (WHO) has put our expectations firmly in place by signalling an 18-month wait.
Meanwhile, Donald Trump has ordered that a coronavirus vaccine be made available by the time of the US presidential elections in November. I suspect the responses to this request from scientists at the National Institute of Allergy and Infectious Disease in Maryland are unprintable.
Let’s look at how vaccines are usually produced to see if there are any putative shortcuts.
The immune system has a memory; if it has encountered a virus before it quickly employs its defences to see off the intruder before a full-blown infection develops. The idea behind vaccines is to give the body a chance to build a memory against a virus it may encounter in the future.
The annual flu vaccine is produced by growing the virus in millions of chicken eggs. This process takes four months. And that is for a vaccine with a long track record of laboratory production. So straight up, producing a Covid-19 vaccine is a greater challenge.
However, on a positive note Sars-CoV-2 (Covid-19) shares between 80 per cent and 90 per cent of its genetic material with the virus that caused Sars in 2002. A vaccine was produced against Sars, albeit too late to be of clinical use. But this vaccine’s existence should help in the initial stages of developing one against Sars-CoV-2.
Protein-based vaccines
In terms of safety, a recombinant vaccine would be a better option. Also known as protein-based vaccines, they use a single component of the virus for vaccination. Most commonly this means using proteins from the surface of a virus. When a real live virus enters the body, these surface proteins are then easily recognised by the immune system, thereby producing an instant defence.
"Theoretically the simplest and fastest way to make a vaccine would be to have a person's own cells produce minute quantities of the viral protein that trigger an immune response," says Prof Jean Peccoud, Abell chair in synthetic biology at Colorado State University.
The main issue with gene-based vaccines is getting the DNA to where it needs to be. One way to solve this challenge is to use a harmless virus as a delivery system. Once inside, a virus with genes from Sars-CoV-2 could use the machinery of the cell to produce proteins to trigger an immune response to the coronavirus.
How does Prof Peccoud see the vaccine race panning out?
“It is unlikely the first vaccines developed will be 100 per cent effective and easy to produce on a massive scale” he says. “Realistically, researchers will develop a number of good-enough vaccines that can be produced using different kinds of manufacturing infrastructures.
“While these vaccines may at first have a limited efficacy, the diversity in manufacturing processes will allow companies to make and distribute them quickly, buying time and helping contain the current epidemic.”
Mutates
Another key element in the coronavirus vaccine story is how quickly the virus mutates. If coronavirus behaves like influenza, and mutates on an ongoing basis, then an annual vaccine will be necessary. However, if it remains stable then it will be more like measles and chicken pox, and a single vaccine shot would provide long-term protection.
Even if the initial vaccines to emerge from the intense scientific effort that is now under way are not perfect, they could bridge us through to the end of the current emergency.
Given where we are now in the pandemic, that is an outcome we would happily settle for.