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Two vaccine doses are needed for good protection against delta variant, study shows


By Beth Gault

17 Aug 2021

Two doses of the Covid vaccine are necessary for good protection against the delta variant, a Public Health England funded study has shown.

The research, published in the New England Journal of Medicine, reported that a two-dose regimen of the Pfizer vaccine was 88% effective against symptomatic disease caused by the delta variant.

A two-dose course of the AstraZeneca jab was also found to be 67% effective against symptomatic disease.

However, it found that one dose of either vaccine was only 30% effective against the delta variant.

The researchers analysed data from the national vaccination register and just over 19,000 sequenced Covid cases between 5 April and 16 May 2021.

Alongside the effectiveness of the vaccine against the delta variant, the study also looked at its effectiveness against the alpha variant. Over 14,000 of the cases analysed by the study were the alpha variant, while 4,272 were the delta variant.

The data showed that two doses of the Pfizer vaccine were 93.7% effective against the alpha variant, while the AstraZeneca was 74.5% effective. One dose of either vaccine was around 48.7% effective against the alpha variant.

The study’s authors said: ‘Only modest differences in vaccine effectiveness were noted with the delta variant as compared with the alpha variant after the receipt of two vaccine doses.

‘Absolute differences in vaccine effectiveness were more marked after the receipt of the first dose. This finding would support efforts to maximize vaccine uptake with two doses among vulnerable populations.’

It comes after NHS England urged people over the age of 18 to get their vaccine ‘as soon as possible’.

Covid vaccine intervals were cut in July to enable everyone over 18 to be double jabbed by the middle of September.

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