As vaccination rates in the U.S. continue to fall, new concerns are rising about a more dangerous variant of COVID-19 that came out of India - the Delta variant. It already accounts for the majority of U.K. cases last week and 6% of the total cases worldwide, leading to the postponement of reopenings in that country. It is 60% more transmissible than the first Alpha variant, which was also 40% more transmissible compared to the original SARS-CoV-2 virus. It also seems to be more dangerous once a person is infected.
The coronavirus mutates easily because its genetic information is in the form of RNA, which is prone to errors when copied. These random mutations can help a virus evade the immune system, make it weaker, or have no effect at all. In the case of the Delta variant, a series of genetic mistakes accumulated on the spike protein, which antibodies use to detect it. The mutations make it harder for antibodies to identify the virus and allow it to escape the immune system even after it is caught. Often, certain mutations that are beneficial to a virus evolve independently in many different areas around the globe and spread more quickly, with this mutation at location 681 quickly becoming more common.
It also seems that this variant is also more resistant to vaccines. In the U.K., 31% of the patients with the Delta variant and needing critical care had at least one dose of a vaccine. With both doses, the Pfizer vaccine appeared to be around 88% effective, and AstraZeneca 60%. With one dose, they were just 51% and 33% effective. What has happened in the U.K. could happen in many other countries if people do not continue to be cautious. It is important that people not let down their guard.
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