“In my opinion, we are approaching herd immunity,” said Prof. Cyrille Cohen. “Why am I saying it? Since, after too many openings, Purim, and Passover, the virus’s replication rate in Israel has remained between 0.7 and 0.8.”
The replication rate, or ‘R,’ quantifies the number of people infected by each virus carrier. When it is less than one, the condition is said to be in decline.
Herd immunity is described by the World Health Organization as “indirect protection from an infectious disease that occurs when a population is immune, either through vaccination or immunity developed through previous infection.” When this occurs, and people that are not resistant are protected from the outbreak because the infection cannot find a suitable 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.
The expectation was quickly dashed when the extremely infectious British version found its way into the country and became the prevalent strain of the virus: without the opportunity to inoculate at least 80 percent of Israel’s nine million inhabitants, experts warned, the goal was out of control.
However, as further sanctions have been relaxed and promising cases have dropped in recent weeks, some analysts have speculated that the nation 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 has a R of 18-20, so herd immunity allows 95 percent of the population to be protected.
“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 most recent official update from the Health Ministry, 63 percent of Israel’s general population is reportedly immune, including 800,000 citizens who have formally recovered from the outbreak.
“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.
Over more than a week, Israel has seen no more than 300 new regular cases, with 3,000 active cases as of Wednesday. At the height of the pandemic, 10,000 patients were diagnosed as positive every day, including tens of thousands of active cases.
Serious cases have also declined gradually, 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 ago, Segal told Channel 12 that Israel might have achieved “a sort of herd immunity.” Prof. Gili Regev-Yochay, head of the Infection Prevention and Control Unit at Sheba Medical Center in Tel Hashomer, had previously made similar comments on 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.”