Having no respite from the Covid-19 pandemic in sight since its emergence early last year, the world is now heavily relying on vaccines, with three billion doses already administered.
But much to the chagrin of researchers, the deadly virus has developed so many super-transmissible variants.
The Atlantic has identified three simple principles to understand how the variants interact. Each has caveats and nuances, but together, they can serve as a guide to our near-term future.
Principal No 1: The vaccines have always had to contend with variants. And in real-world tests, they have consistently lived up to their extraordinary promise. The vaccines from Pfizer-BioNTech and Moderna reduce the risk of symptomatic infections by more than 90%, as does the still-unauthorized one from Novavax. Better still, the available vaccines slash the odds that infected people will spread the virus onward by at least half and likely more. In the rare cases that the virus breaks through, infections are generally milder, shorter, and lower in viral load.
Could the Delta variant change that picture? Data from the UK suggest that it is up to 60% better at spreading than Alpha, which was already 43 to 90% more transmissible than the original virus.
But even against Delta, full vaccination—with a heavy emphasis on full—is effective. Two doses of Pfizer’s vaccine are still 88% effective at preventing symptomatic Delta infections, and 96% effective at preventing hospitalization.
Principle No 2: Unvaccinated people are in more danger than ever because of the variants. Even though they’ll gain some protection from the immunity of others, they also tend to cluster socially and geographically, seeding outbreaks even within highly vaccinated communities.
For instance, since Delta’s ascendancy, the UK’s cases have increased sixfold. Long-Covid cases will likely follow. Hospitalizations have almost doubled. That’s not a sign that the vaccines are failing. It is a sign that even highly vaccinated countries host plenty of vulnerable people.
Delta’s presence doesn’t mean that unvaccinated people are doomed. When Alpha came to dominate continental Europe, many countries decided not to loosen their restrictions, and the variant didn’t trigger a huge jump in cases.
Globally, vaccine inequities are even starker. Of the 3 billion vaccine doses administered worldwide, about 70% have gone to just six countries; Delta has already been detected in at least 85. And new variants are still emerging. Lambda, the latest to be recognized by the WHO, is dominant in Peru.
Principal No 3: Whenever a virus infects a new host, it makes copies of itself, with small genetic differences—mutations—that distinguish the new viruses from their parents. As an epidemic widens, so does the range of mutations, and viruses that carry advantageous ones that allow them to, for example, spread more easily or slip past the immune system to outcompete their standard predecessors. That’s how we got super-transmissible variants like Alpha and Delta. And it’s how we might eventually face variants that can truly infect even vaccinated people.
The WHO’s decision to name variants after the Greek alphabet means that at some point, we’ll probably be dealing with an Omega variant.
