Explained: What will it take to stop delta variant of coronavirus

A more powerful driver of Covid-19 outbreaks than any strain of the coronavirus encountered so far, the delta variant is testing the limits of public health defences globally. The good news is that in most cases, the effectiveness of vaccines at protecting against severe disease is maintained; the vast majority of infections are occurring in unvaccinated people. But vaccines alone don’t provide a fail-safe shield.

Why is delta harder to stop than other strains?

Delta is both more infectious and more capable of evading immunity generated by either vaccination or a previous natural infection. It’s not known exactly why, but scientists believe it’s a combination of factors, including that: It replicates faster and reaches significantly higher concentrations in the up­per airways; it’s expel­led in greater qua­n­tities by infected individuals; its viral particles are better at latching on to the ACE2 receptor, an enzyme found on the surface of many cells that the virus uses to infect them; it may be more efficient at causing infection, by requiring fewer viral particles or a lower infectious dose.

What’s the best defence against delta?

A full course of vaccination is the best way to protect against sickness requiring hospitalisation in the event of a delta infection. It’s necessary that sufficient supplies of vaccine are made available worldwide, and that sizeable majorities in communities get inoculated. Without that, populations will be susceptible to delta-driven epide­mics that will result in large numbers of infections, hospitalisations, and, ultimat­ely, deaths. Where that occurs, eventually enough of those who survive will develop natural imm­unity to reduce the number of people susceptible to the virus, causing transmission to slow and eventually stop. Allowing that to happen would not only create misery in the community and burnout among health-care workers, it would also risk spawning new variants. The more the virus circulates, the more opportunity it has to acquire mutations that enable it to evade immunity or transmit even more readily.

Are vaccines enough?

Health professionals say vaccines won’t be sufficient to stop delta in communities with high rates of transmission. Where that’s the case, they say, additional measures will be necessary to impede its spread. These include the same strategies that were central before vaccines became available. In addition, researchers are calling for ventilation systems to be overhauled.