A new study published on Friday suggested for the first time Israel’s vaccination campaign was proving effective at preventing infection and serious illness in vaccinated individuals.

It adds to an analysis published earlier in the week which shows the Pfizer vaccine starting to change the dynamics of the outbreak in Israel where nearly 40 per cent of the population has now received at least one jab.

The latest study published by Professor Dvir Aran, a biologist at the Technion-Israel Institute of Technology, suggests the vaccine is between 66-85 per cent effective at preventing infection and 87-96 per cent effective for preventing severe disease.

The results are not quite as strong as Pfizer’s own phase three trial results but not far off.

“Our sensitivity analysis provides an estimate for the effectiveness of the vaccine in reducing positive and severe cases”, said the authors. “While this estimate is lower than the efficacy of the [Pfizer trial] it is still substantive and provides reassurance for the vaccine efficacy”.

The degree to which the Pfizer vaccine appears to block infection is the perhaps the strongest signal yet that it may block transmission of the virus - the key to eventually reaching herd immunity.

However, the results also suggest the first dose of the vaccine may not be “very effective” in reducing cases. This raises a possible concern over the UK strategy of leaving 12 weeks between shots, rather than the three weeks recommended by Pfizer.

“We see that immediately after the second dose the effectiveness jumps”, said Prof Aran on Twitter, adding that this could be explained by either the immediate impact of the second dose or the first dose coincidentally becoming effective on the three-week mark. “We will have to wait and see numbers from the UK”, he said.

A second Israeli study shows the vaccination campaign appears to have had a marked impact on case numbers, hospitalisations and serious illness among those over 60 - the first group to be vaccinated.

Among this group, there was a 35 per cent drop in cases, a 30 per cent drop in hospitalisations and a 20 per cent fall in those critically ill over the two weeks to February 1

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