The Delta variant of the Coronavirus changes the theories regarding herd immunity, and this is because the initial percentages estimated as necessary to stop the pandemic are no longer valid, instead of a collective immunity of 60%, one of 80% - 90% is required due to the new variants.
"I saw that in Israel they vaccinated most of them with 2 doses. Cases exploded, 22.000 per day. What is the explanation?”
Israel was among the first countries to achieve a vaccination rate of over 60%, given that they had sufficient vaccine doses available from the start. As such, they decided to drop all restrictions, including the mask indoors (from summer), before the delta variant became dominant.
The increase in the number of cases is explained by the fact that the delta variant quickly became dominant, including in Israel, (the delta variant is highly transmissible and partially evades the immune response after illness or after vaccination) in an unrestricted period, in a population where the elderly most of them had been vaccinated for over 6 months.
Additionally, a vaccination coverage rate of 60% is not considered sufficient to limit the spread of the delta variant.
In addition, Israel has significantly increased testing capacity, far beyond what was being tested in wave 3, so that many asymptomatic infections are being identified. The policy is to find as many cases as possible to isolate and thus limit transmission.
In the context of the spread of the delta virus variant, a vaccination rate of between 80% and 90% is estimated, which is necessary to limit the circulation of this virus variant, which in Israel is not the case now.
An eloquent example is Denmark. They maintained the restrictions during the summer, did a lot of testing and identified cases, accelerated vaccination and reached over 80% coverage, and now they have lifted the restrictions, with no increase in cases."
