Scientists find Delta variant evades immune system, but people vaccinated with full regimen are protected

The Delta variant of the coronavirus can escape antibodies that target certain parts of the virus, according to a new study published Thursday in Nature. The results provide an explanation for the lower efficacy of Delta vaccines, compared to other variants.

The variant, first identified in India, would have is about 60% more contagious than Alpha, the version of the virus that hit Britain and much of Europe earlier this year, and possibly twice as contagious as the original coronavirus. Delta variant now it causes epidemics among unvaccinated populations in countries such as Malaysia, Portugal, Indonesia and Australia.

Delta is now the dominant variant in the United States. Infections in this country had stagnated at their lowest levels since the start of the pandemic, While numbers may rise, virus-related hospitalizations and deaths have continued to drop sharply. It is due partly because of the relatively high vaccination rates48% of Americans are fully immunized and 55% have received at least one dose.

But the new study found that Delta was barely sensitive to a dose of vaccine, confirming previous research suggesting that the variant could partially bypass the immune system, although to a lesser extent than Beta, the variant first identified in South Africa.

French researchers tested to what extent antibodies produced by natural infection and by coronavirus vaccines neutralize Alpha, Beta and Delta variants, as well as a reference variant similar to the original version of the virus.

Researchers examined blood samples from 103 people infected with the coronavirus. The study found that Delta was much less sensitive than Alpha to samples from unvaccinated people in this group.

One dose of vaccine significantly increased sensitivity, suggesting that People who have recovered from Covid-19 still need to get vaccinated to defend themselves against certain variants.

The team also analyzed samples from 59 people after receiving the first and second doses of AstraZeneca or Pfizer-BioNTech vaccines.

Blood samples from only 10% of people immunized with a dose of AstraZeneca or Pfizer-BioNTech vaccines were able to neutralize the Delta and Beta variants in laboratory experiments. But a second dose increased that number to 95 percent. There were no significant differences in the levels of antibodies induced by the two vaccines.

“A single dose of Pfizer or AstraZeneca was poor or ineffective against the Beta and Delta variants,” the researchers concluded. Data from Israel and Britain largely support this conclusion, although these studies suggest that one dose of the vaccine is still sufficient to prevent hospitalization or death from the virus.

The Delta variant also did not respond to bamlanivimab, the monoclonal antibody made by Eli Lilly., according to the new study. Fortunately, three other monoclonal antibodies tested in the study remained effective against the variant.

In April, citing the increase in resistant variants of bamlanivimab, the Food and Drug Administration revoked authorization for emergency use for use as a sole therapy in treating Covid-19 patients.

Apoorva Mandavilli is a journalist who focuses on science and global health. She is the 2019 winner of the Victor Cohn Award for Excellence in Science Reporting medical. @ apoorva_nyc

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