ATHENS — The Delta variant of Covid-19 has increased the percentage of the population that needs to be vaccinated or otherwise immune to stop the virus spreading, Professor of Health Policy at London School of Economics and Social Science Elias Mossialos said in a social media post on Friday.

He said that a 70-75 pct immunity rate – either through vaccination or after infection – will no longer be sufficient and its estimated that this must now increase to more than 82 pct of adults to protect the community. According to Mossialos, those at risk were mainly adults that have not been vaccinated, children (who have also not been vaccinated but have milder symptoms) and some 4-8 pct of people who can become seriously ill due to the Delta variant, in spite of being vaccinated.

According to Mossialos, the vaccines are less effective against the Delta variant, which causes serious illness in 4-8 pct of vaccinated individuals and milder illness in 12-33 pct. The Delta variant is much more easily transmitted, he added, but the data so far do not indicate that it's more lethal.

Asked why the number of cases has increased in countries like the UK and Israel, where significant numbers have been vaccinated, Mossialos said that vaccination rates in both countries remained below 60 pct of over-16s. Adding the 10-15 pct of those that have immunity because they have already had Covid raises this to 70-75 pct with immunity but this appears to be insufficient to control the Delta mutation.

While the UK was the country with the most new cases, he pointed out, it had the smallest number of serious cases, which meant that vaccines work.