Israeli, UK data offer mixed signals on vaccine’s potency against Delta strain
Local research claims Pfizer shot now only 41% effective against symptomatic COVID, while British stats have it at 88%
Nathan Jeffay is The Times of Israel's health and science correspondent
New data from Israel and the United Kingdom painted a confusing and contradictory picture on Thursday as to the effectiveness of Pfizer’s COVID-19 vaccine in fighting off the Delta variant of the coronavirus.
New Health Ministry statistics indicated that, on average, the Pfizer shot — the vaccine given to nearly all Israelis — is now just 39% effective against infection, while being only 41% effective in preventing symptomatic COVID. Previously, the Pfizer-BioNTech vaccine was well over 90% effective against infection.
Meanwhile, a new UK study published this week in The New England Journal of Medicine found the same vaccine to be 88% effective in preventing symptomatic COVID — more than twice the rate found in the Israeli data.
Israel’s research agreed, at least, that the shot was highly effective in avoiding serious illness, at 91.4% effectiveness.
Some analysts have warned that the figures on vaccine effectiveness are prone to major inaccuracies because of a range of factors, including questions over whether there is accurate data on infection levels among the non-vaccinated, which is vital for such stats.
The Israeli statistics also appeared to paint a picture of protection that gets weaker as months pass after vaccination, due to fading immunity. People vaccinated in January were said to have just 16% protection against infection now, while in those vaccinated in April, effectiveness was at 75%.
Doctors note that such figures may not only reflect time that has passed since vaccination, but also a bias according to which those who vaccinated early were often people with health conditions and who are more prone to infection, such as the elderly.
Reacting to the Israeli figures on Thursday, epidemiologist Nadav Davidovitch, a Ben-Gurion University professor and leader of Israel’s doctors’ union, told The Times of Israel, “What we see is that the vaccine is less effective in preventing transmission, but it’s easy to overlook that it’s still very effective in preventing hospitalization and severe cases.”
Davidovitch added: “It’s still excellent, very good in preventing severe cases and death, but less so in preventing transmission. And this is why we can’t rely on vaccinations alone, but also need Green Passes, testing, masks, and the like.”
Davidovitch stressed that all figures should be treated as preliminary and with limited relevance given the relatively small numbers of positive patients at the moment. “It’s quite early to comment, as the number of positive people is still quite low,” he said.
He spoke after ministers approved reinstating the Green Pass, limiting attendance at large events to those who are vaccinated, have recovered from COVID-19, or who present a valid negative test result.
The renewed restrictions will apply to both indoor and outdoor events with over 100 participants, starting on July 29. The requirement to present proof of vaccination, recovery or a negative test from the past 72 hours will only apply to people older than 12. Under that age, there will be no restrictions.
The decision was approved by the so-called coronavirus cabinet, a high-level ministerial forum tasked with leading the government’s pandemic response. It must still be ratified by the government, and is set to be voted on Sunday during the weekly cabinet meeting.