Pfizer vaccine efficacy ‘decreases against Delta variant’

Data from Israel suggests jab is less effective at preventing infection with rapidly spreading strain of Covid

Israeli medical worker
Medical worker prepares a dose of the Pfizer-BioNTech vaccine in Tel Aviv
(Image credit: Jack Guez/AFP/Getty Images)

The effectiveness of the Pfizer-BioNTech vaccine in preventing Covid infection and symptomatic illness has dropped in Israel as the Delta variant spreads, according to a preliminary study.

The decline, reported by the country’s health ministry, has also coincided with the lifting of almost all coronavirus restrictions on 1 June, Israeli news site Ynet reports.

Data for the past month shows that the jab’s efficacy was 64% after two doses, down from 94% in May. But the vaccine was still 93% effective in preventing hospitalisations and serious illness - a relatively small drop from 98.2%.

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Uptick in infection

“Israel has been one of the most successful countries in the world in tackling the pandemic,” says the BBC.

According to latest Oxford University tracking, 60% of Israel’s 9.3 million population have received both jabs, compared with about 50% in the UK.

After then prime minister Benjamin Netanyahu became the first person in Israel to receive a shot, on 19 December, the average number of daily confirmed Covid cases hit more than 8,000 in January but then declined to reach just double digits in May.

However, “cases have ticked up since Israel lifted all remaining Covid-19 restrictions” at the start of June, reports the Financial Times. And experts are “blaming the highly transmissible Delta variant”, which was first detected in India.

A total of 324 new infections were reported in Israel yesterday, although the number of Covid-related deaths has remained very low.

The Delta variant is thought to be responsible for 90% of new cases recorded over the past two weeks in the country, which has used the Pfizer-BioNTech jab for “almost all vaccinated Israelis”, says The Times of Israel.

‘Preliminary signal’

Public Health England (PHE) has “also documented a drop in efficacy for the Pfizer jab against the Delta variant, though less severe”, says the FT.

A PHE study published in May found that the jab offered 88% protection against symptomatic infection from the Delta strain after two doses, compared with 93% against the Alpha variant (also known as the Kent variant).

In Israel, about half of adults infected during the ongoing Delta outbreak were fully inoculated with the Pfizer vaccine. The chair of Israel’s National Expert Panel on Covid-19, Ran Balicer, told the AFP news agency yesterday that the rise in new cases was a “preliminary signal” of “some decrease in vaccine effectiveness against mild illness - but not severe illness”.

But he stressed that it was “too early to precisely assess vaccine effectiveness against the variant”.

Responding to the new Israeli data, New York-based pharmaceutical giant Pfizer noted that the study was still preliminary and that existing evidence has shown that the jab works against a number of variants of concern, including Delta.

Covid variants table

Contrast to UK

Israel’s reaction to the surge in Delta infections “stands in contrast with that of the UK”, says the FT. While Boris Johnson is pressing forward with a full lifting of Covid restrictions from 19 July, Israel is considering reintroducing the measures removed there last month.

Mandatory masks in public enclosed spaces have already been reinstated in a bid to stem the rise in cases, while doctors are calling for ministers to roll out vaccine booster shots.

And the Israeli government’s coronavirus cabinet is meeting today “to consider the reinstitution of restrictions” including social gathering limits, along with a return to the country’s “green passport” scheme for people who have been fully vaccinated, reports Ynet.

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