Israel data shows Pfizer jab protects against virus but immunity unclear
Initial data from Israel's closely-watched coronavirus vaccination campaign proves the Pfizer/BioNTech vaccine protects against serious illness but offers no conclusion yet on progress towards herd immunity, experts say.
The Jewish state is carrying out what is widely described as the world's fastest vaccination campaign per capita.
Many countries are struggling with vaccine supply but Israel has not experienced shortages since launching inoculations in December.
It secured its substantial stock by paying above market price and, more importantly, through a data sharing agreement with Pfizer.
The agreement stipulates that Israel, which has one of the world's most sophisticated medical data systems, will share real-time information with Pfizer on the vaccine's impact, including on progress towards achieving herd immunity.
So far, Israel has given the first of the two recommended Pfizer jabs to roughly 35 percent of its nine-million population. About 1.8 million have also received the second jab, mostly those over 60.
- Direct vs Indirect protection -
Ran Balicer, chairman of Israel's national expert panel on Covid-19, told AFP it was crucial to distinguish between the vaccine's two impacts.
The first is "the direct effect", which refers to vaccinated people becoming "protected against symptomatic illness and severe disease", he said.
The second, or "indirect effect," refers to the vaccine providing enough immunity to enough people that it forms an "epidemiological barrier" against transmission.
Balicer, also the chief innovation officer at Clalit, Israel's largest health maintenance organisation (HMO), said the data shows the vaccine reduces serious illness but the immunity question remained open.
Gabi Barbash, a prominent public health expert currently with the Weizmann Institute of Science, agreed: "We do know that vaccines are decreasing the incidence of severe disease. That's it," he told AFP.
"We do not know whether the vaccines are minimising transmission."
- Phase IV -
In November, Pfizer announced that its Phase III trial showed 95 percent efficacy against the virus.
Given the gravity of the pandemic, Pfizer received regulatory approval through an accelerated trial process, which has increased the importance of Israel's more comprehensive data.
Israel's Maccabi Institute of Innovation and Research, linked to an HMO of the same name, published a paper this week that it described as "the first and largest Phase IV study on the effectiveness of the (Pfizer) vaccine".
Clalit and Maccabi are two of Israel's four HMOs, which collectively provide healthcare to the entire population.
The HMOs are directly responsible for vaccinations and collecting data on their impact.
Maccabi compared the incidence of Covid-19 in the 12 days after an individual received their first Pfizer shot against incidence 13 to 24 days after the jab.
This data showed a 51 percent reduction in the incidence of lab confirmed infection in the latter period.
"Two weeks after the first dose you see a significant reduction in infection but it is not complete," Gabriel Chodick, co-author of the Maccabi report told AFP.
Israel is also only testing those who present coronavirus symptoms, not a randomised sample of the entire vaccinated population.
It therefore does not have comprehensive data on the number of vaccinated people who are carrying the virus without symptoms.
- Two jabs -
Pfizer recommends its product be administered in two doses, spaced three weeks apart.
Because Israel is well-stocked, it is giving the second jab in line with Pfizer's recommendations, meaning it does not have data on whether the protective effect from just one jab would increase after 24 days, in the absence of a second jab.
Maccabi has also released preliminary data on the second jab's impact.
It showed that out of 248,000 people studied one week after receiving their second injection, only 66 mild coronavirus infections were registered.
While those figures point towards near total protection, Maccabi has stressed this data has not been subjected to a full scientific analysis.
- High case count -
During the vaccination campaign, Israel has continued to register daily caseloads above 5,000, despite a nationwide lockdown in place since December 27.
But compliance with, and enforcement of, the lockdown has been uneven, notably among ultra-Orthodox Jews who have persistently flouted public safety rules throughout the pandemic.
"If you look at the number of new identified positive corona cases per day, it has not decreased for the last month and half," Barbash said.
"So is it because the lockdown is not a (real) lockdown, or is it because the vaccine is not minimising transmission? No one can tell that."
© 2021 AFP