Indian origin variant of coronavirus, known as “Delta”, easily transmissible form of the virus, has spread to at least 77 countries and regions. The Centers for Disease Control and Prevention has identified it as a “variant of concern.” Studies to date suggest the Delta variant is between 40 and 60 per cent more transmissible than the Alpha variant first identified in the U.K.—which was already 50 per cent more contagious than the original viral strain first detected in Wuhan, China.
Delta has quickly become the dominant variant in the U.K. and has led to another surge in cases there, despite the population’s high vaccination rate.
A study in Scotland, published in the Lancet, found the hospitalization rate of patients with that variant was about 85 percent higher than that of people with the Alpha variant. But because of the time lag between hospitalizations and deaths, there is not enough data to say whether or not Delta is more deadly than other variants. “The thing we were surprised by is just how rapidly the Delta variant took hold,” says Aziz Sheikh, a professor of primary care at the University of Edinburgh and lead author of the Lancet study. “We were again in an exponential phase of growth of cases.” This should be a lesson for the U.S., he says.
Fortunately, vaccination appears to provide good protection against Delta—although one dose seems to offer less protection than it did against other variants. A preprint study by Public Health England found that two doses of the Pfizer-BioNTech vaccine and two doses of the AstraZeneca vaccine were 96 per cent and 92 per cent effective, respectively, at preventing hospitalization in people infected with Delta That result is comparable to the level of protection seen against other variants. Meanwhile, a single dose of the AstraZeneca vaccine was only 71 per cent effective against hospitalization caused by Delta (a single dose of Pfizer was still 94 per cent effective), and one shot of either vaccine was only about 33.5 per cent effective against symptomatic COVID from that variant, highlighting the importance of getting both doses. The U.K., which had postponed second doses in an effort to vaccinate a larger portion of its population quickly, has now delayed its reopening plans by four weeks to allow time for more people to get both doses.
