The 3 Simple Rules That Underscore the Danger of Delta

Vaccines are still beating the variants, but the unvaccinated world is being pummeled.

 
Fifteen months after the novel coronavirus shut down much of the world, the pandemic is still raging. Few experts guessed that by this point, the world would have not one vaccine but many, with 3 billion doses already delivered. At the same time, the coronavirus has evolved into super-transmissible variants that spread more easily. The clash between these variables will define the coming months and seasons. Here, then, are three simple principles to understand how they interact. Each has caveats and nuances, but together, they can serve as a guide to our near-term future.

 
1. The vaccines are still beating the variants.

The vaccines have always had to contend with variants: The Alpha variant (also known as B.1.1.7) was already spreading around the world when the first COVID-19 vaccination campaigns began. 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 percent, 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. As of June 21, the CDC reported just 3,907 hospitalizations among fully vaccinated people and just 750 deaths.

Could the Delta variant (also known as B.1.617.2) change that picture? Data from the U.K. suggest that it is 35 to 60 percent better at spreading than Alpha, which was already 43 to 90 percent more transmissible than the original virus. (It may also be deadlier, but that’s still unclear.) It now causes 26 percent of new infections in the U.S. and will soon cause most of them.

But even against Delta, full vaccination—with a heavy emphasis on full—is effective.  Two doses of Pfizer’s vaccine are still 88 percent effective at preventing symptomatic Delta infections, according to a U.K. study, and 96 percent effective at preventing hospitalization. (A single dose, however, is only 33 percent effective at stopping symptomatic infection.) Israel, a highly vaccinated country, is experiencing a small Delta surge, but so far, none of the new cases has been severe. And while about 30 percent of those new cases have been in fully vaccinated people, this statistic reflects, in part, the country’s success at vaccination. Because Israel has fully vaccinated about 85 percent of adults, you would expect many new infections to occur in that very large group. “It does seem like the vaccines are holding their own against the variants,” Emma Hodcroft, an epidemiologist at the University of Bern, told me. “That’s something we can take some comfort from.”

But the coronavirus can cause serious problems without triggering severe infections. Because people can develop long COVID without ending up in the hospital, could Delta still cause long-term symptoms even if vaccines blunt its sting? The anecdotal reports of long-haulers whose symptoms abated after vaccination might suggest otherwise, but “we don’t know enough to say,” Bill Hanage, an epidemiologist at Harvard, told me.

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Πηγή: theatlantic.com