Zero Covid strategies are coming to nought, globally. But vaccines and Covid-appropriate behaviour can take the sting out of the virus

Even as China doubled down on its “zero Covid” strategy in the past week, government spokespersons in Australia and New Zealand have started expressing doubts about persisting with this strategy.

Australian Prime Minister Scott Morrison said that it is highly unlikely that his country would ever return to zero-Covid cases. New Zealand’s Covid-19 Response Minister Chris Hipkins admitted that the highly infectious nature of the Delta variant has raised “pretty big questions” about the approach to “eliminate the disease”. These two countries had till recently experimented with a “travel bubble” between them, while keeping out travellers from other countries, hoping to permanently close the door on the virus.

Singapore had earlier given up on the zero-Covid strategy and Israel is beginning to acknowledge that its much acclaimed war to crush the virus is ending in a stalemate. Most other countries are getting reconciled to the notion that we will have to live with the virus, while preventing severe disease and death through extensive vaccination. Even the protection offered by vaccines is now appearing to be less of an impenetrable shield and more of a buffering vest that absorbs much of the bullet’s force, resulting in mostly mild breakthrough infections. Tom Frieden, former director of the Centers for Disease Control in the USA, recently commented that there is much that we don’t understand about this virus.

Yet, there is. If not specifically about this virus, we do know about the evolutionary biology of other microbes, to start eschewing the war-like slogan of eradication. The only two microbes that have been completely eradicated so far are smallpox in humans and rinderpest in cattle. Even polio has not been eradicated all over the world — it still lurks in Afghanistan and Pakistan. Getting rid of the coronavirus completely is an unrealistic ambition, especially since it is a respiratory virus that spreads far and fast. Indications are clear that the only winning strategy we have is to protect people from severe disease through vaccination and use tested measures to contain transmission till we vaccinate a large majority of the global population. By doing so, we should aim to steer the virus towards becoming milder even as it continues to be a presence in our world.

Cautionary counselling, that we should not sound militaristic calls for microbial eradication in our response to infectious agents, comes from a scientist who won the Nobel Prize for Medicine and Physiology at a very young age in 1958 — Joshua Lederberg. In a seminal essay on the history of infectious diseases, published in Science in 2000, he advises us to discard the “waging war” metaphor and recognise the evolutionary imperatives that drive the microbe’s behaviour. Lederberg suggests that “a successful parasite (one that will remain infectious for a long time) tends to display just those epitopes (antigenic fragments that stimulate the immune system) as will provoke responses that a) moderate but do not extinguish the primary infection and b) inhibit other infections by competing strains of the same species or other species”. Is the Delta variant racing to claim that crown or will yet another variant emerge to achieve a better balance between high infectivity and continued presence among the human population, which it will seek to use for replication but be careful not to extinguish?

Microbes evolve much faster than humans. However, we can exert evolutionary pressure on the virus by creating barriers for its easy transmission and prevent a prolonged stay in infected humans whereby it finds enough time to mutate. We do the former by using masks, moving in well-ventilated areas and avoiding crowds. All of these are especially needed when we know that the virus has a highly infectious spread through aerosols that move far beyond six feet. We achieve the latter objective, of limiting the duration of viral presence in the bodies of infected persons, through effective vaccines. By simultaneously pursuing these twin strategies, we can exert evolutionary pressure on the virus to become milder in virulence, albeit more infectious when given the opportunity.

Why will the virus become less virulent over time? Because its survival advantage depends on having a human host, in whom it can replicate. It cannot afford to wipe out our species, for it will script its own extinction by doing so. Why then does the SARS-CoV-2 virus still kill so many across the world? Lederberg’s essay provides an explanation. He writes: “Those relatively few infectious agents that cause serious sickness or death are actually maladapted to their host, to which they may have only recently gained access through some genetic, environmental or sociological change.” That fits the SARS-CoV-2 virus so well! The virus can still be made to adapt through human strategies.

Eradication of the virus is also a difficult goal to reach when there are alternate hosts where the virus can find refuge and from whom it can re-emerge to infect humans. There are reports now of minks, cats, dogs, lions, tigers, gorillas and white tailed deer being infected with the virus. These can potentially become reservoirs, while the vastly numerous and highly mobile human population will remain the favourite vehicle for the virus to hitchhike its way across the world. It can and will slip through lockdowns. Like love, as Shakespeare declares in Venus and Adonis, the virus too laughs at locksmiths.

Human societies have to resume economic and social activities, albeit with caution. We cannot be living with long lockdowns, lest we irreparably harm the future of our children. We must free ourselves from the obsession with zero-Covid, while we vigorously nudge the virus to become a less threatening co-habitant of our shared planet.

The failure of the zero-Covid strategy also calls for renewed commitment to global solidarity. If all of humanity does not collectively practise transmission containment norms and the vast majority of people in all countries is not vaccinated, the virus can emerge with new mutants that do not reduce their virulence even as they infect with ease. The evolutionary pressure has to be exerted by the host species as a whole, not in pockets. That realisation must change the behaviour of anti-maskers, vaccine opponents and vaccine hoarding nations. Otherwise, the virus will feast on our follies to kill many more, even though its evolutionary instinct is not to do so.