Israeli study recording 33 per cent vaccine effectiveness only covers first 14 days

UK chief scientist says study only useful after 14 days


This picture taken on November 23, 2020 shows a bottle reading "Vaccine Covid-19" next to US pharmaceutical company Pfizer and German biotechnology company Biontech logos on November 23, 2020. (Photo by JOEL SAGET / AFP) (Photo by JOEL SAGET/AFP via Getty Images)

A study by Israeli scientists of preliminary data from 200,000 people who have received the Pfizer/BioNTech coronavirus vaccine has confirmed “really good news” about its performance – but has raised questions over the UK’s decision to delay giving the second dose of the jab.
Professor Ran Balicer, a physician, epidemiologist and chief innovation officer for Clalit, the largest health care provider in Israel, confirmed the first real world study of the vaccine suggested it was 33 per cent effective 14 days after it had been given.
This raised questions about the decision taken by the UK government's vaccine advisers, the Joint Committee on Vaccination and Immunisation, (JCVI) , to delay giving people the second dose of the Pfizer jab for up to 12 weeks.
It was suggested that those receiving the first dose in the UK would have 89 per cent protection against symptomatic Covid-19.
However, on Wednesday Sir Patrick Vallance, the UK’s chief scientific adviser, said the study focused on the first 14 days after the vaccine was administered, and the result for that would always be low since the vaccine does not begin to take effect until at least ten days after the injection, and some people will have been infected when vaccinated.

He said the real interest in the study would be when it released information for days 14-28 after injection: “If you take from day 10 up until day 21 and beyond then it looks much more like the 89 per cent figure the JCVI said. That is the clinical trial data, And we also know that when you get into real world practice things are seldom as good as the trial.
“I think the 89 per cent figure is the figure you see post 10 days. “
Israeli scientists also  believe their 33% figure will rise when data is compiled from younger age groups, and the fact that the data is real-life adds to their confidence. 

"We compared 200,000 people above the age of 60 that were vaccinated. We took a comparison group of 200,000 people, same age, not vaccinated, that were matched to this group on various variables..." Prof Balicer said.
"Then we looked to see what is the daily positivity rate... And we saw that there was no difference between vaccinated and unvaccinated until day 14 post-vaccination.
"But on day 14 post-vaccination, a drop of 33% in positivity was witnessed in the vaccinated group and not in the unvaccinated... this is really good news.
"The data and estimates I gave are what we have.
"We could not see [the clinical trial reported figure of] 89% reduction in the data we reported. Further data and analyses will be released in peer reviewed scientific format."
He added: "The practice in Israel is to provide the second vaccine at three weeks."

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