When will the COVID race be run?
Steve Griffin taking us back to pandemic basics
I’m often asked: is the COVID race really run, or, alternatively, will it ever end?
My answer is that a pandemic race rarely ever ends, but it certainly changes pace and tempo. What matters more is how it’s run. First, we must recognise that it’s a team event, and should prepare for the proverbial marathon, not a sprint. Moreover, we run parallel races at the individual and population level.
The virus
The cause of all this is a strand of nucleic acid. Like all viruses, SARS-CoV2 is a parasite that exists solely to amplify itself and spread. It hijacks our cells, turning them into factories that copy its genome and build protective particles that ferry progeny to the next host. It doesn’t care what collateral damage is done, which can range from deadly or profound to ostensibly absent…why is this?
Any viral infection can be thought of as a race between the virus and our immune systems, set against the environment defined by things like age, other health conditions, and resilience (e.g. malnutrition). Our starting blocks are set by the diverse genetics behind our immunity, whereas the virus depends upon infectiousness, virulence, and initial exposure.
Our first encounter inevitably begins with the virus having a head-start. Nevertheless, our immune systems generally catch up quickly enough to limit the damage. However, genetically diverse populations always have some individuals making extremely good, or much poorer responses than average. Survivors prime their immune system to respond more quickly and aggressively to subsequent encounters with the virus. If this stops the race (i.e no further infections), we call this “sterilising immunity”, but things are rarely that cut and dried. Regardless, acquiring “natural” immunity from infection carries inherent risk.
Then there is the virus itself. Viruses have myriad survival strategies, but for the type we’re considering – e.g. SARS-CoV2 and influenza – a major factor is their ability to change. Primarily this involves alteration of immune targets - the leopard literally changing its spots.
In simple terms, the pace the virus sets is balanced between its infectiousness and the supply of susceptible versus immune hosts. When a virus first crosses from animals into humans, literally everyone is susceptible. Infections grow exponentially: an “epidemic”. When this occurs simultaneously in multiple countries, we declare a “pandemic”.
Conversely, where population immunity is high, the susceptible minority usually comprise young children (who’ve not been exposed before) or those with lowered immunity. Hence, races become more predictable, although short bursts of population wide infections may occur. This scenario is termed “endemic”. Importantly, it neither reflects prevalence or severity (e.g. Malaria and tubercolosis remain global killers), hence using “endemic” as a platitude is both misleading and ill-informed.
How pandemics progress
The simplest pandemic race involves widespread infection leading to survivors with sterilising immunity, so the pattern settles quickly into endemicity after one or two large waves. This has been the rough pattern for the four major influenza pandemics since 1918.
However, when viruses can change their spots (mutate rapidly), this lessens protection from prior immune responses. Such “drift” in seasonal influenza is sufficient to cause divergence between the virus and population immunity, increasing susceptibles and promoting waves of infection, albeit predictably. Hence, NHS winter pressures happen every year as flu is a serious illness for many.
Clearly, the quicker we can catch up to the virus, the better. Vaccines allow us to move our starting blocks to the same place as if we’d already run the first race, only with no virus involved. This route to achieving immunity while bypassing infection-associated harms has saved countless lives.
Frustratingly, SARS-CoV2 has decided to write its own pandemic playbook. The virus displays a surprisingly high and long-lasting tolerance of mutational changes, combined with an inherently much higher infectivity compared to influenza. A recent study rated its evolutionary rate at two times higher than the fastest seasonal flu, H3N2.
Rapid evolution means greater divergence between emergent virus strains and pre-existing immunity. Eight dominant versions of the virus have generated waves since 2020, along with various sub-lineages, and the virus continues to mutate rapidly.
Such viral variability means that sterilising immunity against transmission isn’t yet achievable; that’s not to say there isn’t a protective effect from vaccines or prior infection - there absolutely is! When anti-vax protagonists bash COVID vaccines by saying you can still infected after vaccination, they merely reveal their lack of understanding. An out-of-date influenza vaccine would be similarly ineffectual. Vaccines against the highly invariant measles virus are essentially identical to those deployed in the 1960s only because measles has not mutated significantly.
SARS-CoV2 remains too dynamic to confidently predict vaccines ahead of time like influenza. Nevertheless, this doesn’t seem to stop the influenza playbook being used here in the UK, apart from the glaring omission of not protecting our children.
Clinically vulnerable people
Does this matter? It is certainly the case that the individual risk of severe acute COVID has been dramatically reduced by vaccines and previous infections. Protection from severe disease lasts much longer than protection from infection, and thankfully the peaks of hospitalisations and deaths are nothing like the pre-vaccine era. Nevertheless, unlike seasonal influenza, COVID comprises the underlying cause on ~60-70% certificated deaths where COVID is a causal factor, even now in 2024. Almost three thousand deaths have already been registered in 2024 to the 1st March.
However, individual risks are not uniform. They are millions of clinically vulnerable people in the UK, including 100,000s who don’t respond well to vaccines. This latter group is more likely to both become infected and suffer severe disease, making it impossible for them to “live with” the virus as things stand. Such health inequality is unethical and unacceptable in a country with supposedly advanced health and social care.
Long COVID and other longer term impacts of the virus
Apart from acute illness, Long COVID and other post-acute sequelae continue to affect millions across the country, affecting all ages including children. Post-viral syndromes are not new, but they have historically been neglected, as ME/CFS sufferers know. Long COVID shares some common features with other post-viral conditions, but is also distinct. Moreover, the sheer scale of the problem is unprecedented.
Other longer term impact also continue, including cardiovascular, neurological, and metabolic problems (e.g., type 1 diabetes). Again, whilst overlaps with other infections can occur, prevalence makes this a major issue. Critically, vaccination (not infection) seems the only way of reducing such harms, and new therapies are desperately needed.
Simple and effective mitigations
We can slow the virus down by forcing it to run on the outside lane and into a stiff headwind. If we can build on the bedrock of vaccination by reducing airborne transmission of SARS-CoV2, both illness and its evolution will reduce. This does NOT involve harsh restrictions or lockdowns. We possess the technology to make indoor environments much more resilient to airborne transmission (of all airborne viruses!), but the level of such investment in the UK is poor. This feels insane given the forthcoming Class Act trial extols the benefits of HEPA filtration for school absences, whilst a recent report from the Royal Academy of Engineering estimated that benefits from improved ventilation could exceed costs by up to £174Bn over sixty years.
Simple physics and other overwhelming evidence support use of FFP2/3 masks for both protection and source control (particularly important in health care settings), further limiting transmission. Restoring at least wastewater surveillance, personal LFD testing, and supported isolation will improve awareness, and further reduce exposure of vulnerable people.
Mitigations will help, but improved next generation vaccines provide real hope of eventually catching up with or overtaking SARS-CoV2. Sadly, the present UK vaccine-led strategy entirely lacks comprehensive vaccination, which is both counterintuitive and contrasts starkly with countries like the USA. The lack of a preschool COVID vaccination programme remains bewildering, both to reduce the acute and long-term harms in kids, and to ensure a long-term reliable level of population immunity.
Mitigations and providing reasonable adjustments may not be politically popular, but ethically we must recognise that a considerable proportion of the population lacks a fair opportunity to genuinely live with SARS-CoV2. Mitigations like clean indoor air will further help them and protect us - from Coronavirus, flu, colds and the next airborne pandemic.