The Jerusalem Post
Israel nearing herd immunity, expert says
Israel is approaching herd immunity against corona, which has allowed the country to celebrate recent holidays and gradual rounds of openings without experiencing any new outbreaks, according to the head of the immunotherapy laboratory at Bar-Ilan University.
Despite corona, more than 20,000 immigrated to Israel this year,
“My opinion is that we are nearing the state of herd immunity,” said Prof. Cyrille Cohen. “Why do I say it? Because even after so many openings, and Purim, and Passover, the reproduction rate of the virus in Israel has
remained between 0.7 and 0.8.”
The reproduction rate, or ‘R’, measures how many people each virus carrier will infect. When it is lower than 1, the disease is considered in recession.
The World Health Organization defines herd immunity as the indirect protection from an infectious disease that happens when a population is immune either through vaccination or immunity developed through previous infection. When such a situation is achieved, even those who are not immune themselves are shielded from the disease
because the virus does not find the right environment to spread.
When Israel launched its vaccination campaign in the second half of December, authorities and health experts hoped that herd immunity could be reached despite children under the age of 16 – about three million people - not being eligible for the shot.
As the highly contagious British variant made its way into the country and became the dominant strain of the virus, the hope was soon abandoned: without the ability to inoculate at least 80% of Israel’s nine million citizens, the target was beyond reach, experts warned.
However, as more restrictions have been lifted while positive cases plummeted in the past few weeks, some experts have suggested that the country might already be there.
“Herd immunity is not a black or white notion – the closer you get to it, the less the virus will propagate,” said Cohen, noting that there is a simple mathematical formula to calculate what percentage of the population needs to be protected in order to stop each disease: 1–1/R, with R representing each disease’s reproduction rate when a virus is left to spread unchecked.
“In the case of the original strain of the coronavirus, the R stands at 3, which tells us that herd immunity can be reached with about 66% of the population covered,” Cohen said. “The R of the British variant, which is considered some 70% more infectious than the original strain, stands at around 5, and therefore requires about 80% of the population covered.”
Measles’ R stands at 18-20, so herd immunity against it requires 95% of the population to be covered.
“The R is influenced by several factors, including social distancing, closures and so on,” Cohen said. “Wearing a mask already cuts the R.”
According to the latest Health Ministry’s official update, 63% of Israel’s general population is currently immune, including 800,000 people who have officially recovered from the virus.
“The real number might be higher,” Cohen explained. “I think that today in Israel at least 70% of the population is protected,” which is why the number of cases remains extremely low.
As of Wednesday, Israel experienced no more than 300 new daily cases for over a week, with active cases standing at 3,000. At the peak of the pandemic, some 10,000 people a day were diagnosed as positive, with tens of thousands of active cases.
Serious cases have also steadily decreased from 390 on March 31, to 300 on April 7 and 219 on Wednesday.
“Israel’s 73rd Independence Day also marks its exit from COVID-19, at least for now,” tweeted Prof. Eran Segal, a computational biologist at the Weizmann Institute of Science. “Since a mid-January peak: there are 98% fewer cases, 93% fewer critically ill patients, 87% fewer deaths, 85% of 16 year olds have either been vaccinated or infected and are therefore immune. Life is returning to pre-covid. Remaining restrictions
can probably be lifted.”
Three days earlier, Segal told Channel 12 that it is possible that Israel has reached “a sort of herd immunity.” Before him, Prof. Gili Regev-Yochay, director of the Infection Prevention and Control Unit at Sheba Medical Center, Tel Hashomer, made similar remarks at KAN Reshet Bet radio.
“If we have just 200 daily cases, what are the chances of getting infected in a gathering?” Cohen concluded. “I believe that considering our current situation, if nothing changes with variants, if we continue to track infected people in a precise way in order to cut the transmission chain, which is more feasible now with a low number of cases than it was in the past, we indeed have a level of protection that goes beyond individual immunity.”