A virology expert says Boris Johnson is making the right call in extending England's lockdown restrictions.

The British Prime Minister has delayed the easing of restriction by four weeks, from next Monday to July 19 due to rising cases of the Delta variant of Covid-19.

Cambridge University's Chris Smith, founder of the Naked Scientist podcast, says the original date was set when the UK was dealing with a less transmissible variant of the virus.

He told Mike Hosking Johnson is changing his plan in response to a changing situation, with the Delta variant taking hold.

“The effect of that was to mean that more people were getting infected more quickly than the modelling had predicted. And that meant that the disease was outpacing the best efforts to vaccinate the population.”

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