Delta variant pushes herd immunity threshold up to 85%

10.07.2021 - 15:56
Delta variant pushes herd immunity threshold up to 85%
It is now necessary to vaccinate about 85 percent of the Faroese population to achieve herd immunity

The hyper-infectious Delta variant of Covid-19, previously known as the Indian variant, is spreading fast across the world and has also made its way to the Faroes.

The basic reproduction number, denoted by ‘R0’, measures the average number of people who can be infected by a typical infected individual.

According to doctor Marnar Fríðheim Kristiansen, the R0 for the original Covid strain is about 3. The Alpha variant, previously known as the UK variant, has an R0 of 4.5, while the Delta variant has an R0 of 7.

From 66 to 85 percent

If we only had the original variant, he explains, 66 percent of the Faroese population would need to become immune to achieve herd immunity. With the Alpha variant, this percentage goes up to 78, and with the Delta variant, a full 85 percent of the population would need to become immune.

“The R0 figure assumes that no efforts are made to contain the virus,” explains the doctor.

“Our contact tracing efforts are quite extensive, and a large proportion of our population are willing to get vaccinated. So I am confident that we can achieve herd immunity.”

He does concede, however, that we might need to open up for vaccinations of the 12-15 age group to reach 85 percent. The health authorities are still debating whether to include this age group in the vaccination programme.

“It makes good sense not to relax our current restrictions too much until we reach this 85-percent mark.”

 >> SEE ALSO Vaccine eligibility extends to ages 16+

A recent study carried out in Israel suggests that the Pfizer/BioNTech vaccine is less effective against the Delta variant than initially thought.

Kristiansen acknowledges the results from this study, but he is keen to point out that this is only one of many similar studies.

“The Israeli study found that the Pfizer vaccine is 64-percent affective against the Delta variant, but other studies suggest an effectiveness of about 75-85 percent,” he says.

“What is perhaps more important is that the Israeli study found the vaccine to be 93 percent effective in preventing serious illness and hospitalisation for those who do get infected.”


For further information about Covid-19 in the Faroes, visit

Read the Faroese version of this article here.

Translated by

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