One Shot Hardly Protects Against Delta Variant, 2 Shots Do

The contagious Delta variant of the coronavirus is complicated to eliminate. People need two shots of a corona vaccine to be protected, but the immune system is much weaker than with other variants even then.

People who have had one shot are hardly protected, and the same applies to people who have been cured of the corona.

French virologists have investigated the strength of the Delta variant, which appeared in India at the end of last year and was therefore first called the Indian variant. In many countries, including the Netherlands, this variant is now dominant. The researchers write about their findings in an article that the essential scientific journal Nature published on Thursday.

The scientists conclude that the Delta variant is very capable of bypassing the immune system. The antibodies of people who have not been vaccinated but who have had corona work reasonably well against the Alpha variant (formerly the British variant). However, the same antibodies have hardly any effect on the Delta variant, and they are four times as weak as with the Alpha variant.

The researchers compared this with the defences of people who have had one shot of the corona vaccines from Pfizer/BioNTech or from AstraZeneca. At about 10 percent, the defences were able to take out the Delta variant. This means that the vast majority of people can become infected and sick after just one shot.

After the second injection, 95 percent of the people had built up enough immunity. But their defences were also less strong against the Delta variant than against the Alfa variant. “A single dose of Pfizer/BioNTech or AstraZeneca was not or hardly effective against the Delta variant. Both vaccines produced a response that was able to neutralize the Delta variant only after the second shot effectively,” the researchers said.