There are 25 coronavirus variants “under monitoring”, Public Health England’s strategic COVID-19 response director has told MPs.

Dr Susan Hopkins told the Science and Technology Committee: “We’re living in a world of variants now, so everything we see is a variation of the original.

She said eight COVID-19 variants are “under investigation”, along with the 25 that are being monitored.

“All of them have mutations that we’re concerned about, but mutations alone are not enough to predict whether it’s really going to impact on our journey through vaccines and impact on the public health risk of hospitalisation,” she added.

Dr Hopkins explained how every variant that does not go “extinct very rapidly” is either going to have a “transmissibility advantage or an immune evading advantage”.

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The 25 variants under monitoring appear to be higher than the most recent technical briefing from Public Health England on 11 June, which showed 13 variants under monitoring, eight under investigation and five variants of concern.

Dr Hopkins also told the committee that if the Delta (Indian) variant was “unmitigated”, left to spread without any lockdown restrictions, the R number could become “greater than five and maybe up to seven”.

“We’re seeing it as much greater transmissibility than Alpha, which had greater transmissibility than the viruses that had gone before unmitigated – so if we were in the real world where we had none of the measures that we were seeing right now – we would estimate R greater than five and maybe up to seven,” she told MPs.

She went on to stress the importance of getting vaccinated, saying it is a “clear mitigation measure”.

The health secretary said last week Delta now makes up 91% of new UK coronavirus cases.

Earlier today, Whitehall sources said the government is to make coronavirus vaccinations compulsory for care home staff who work with elderly and vulnerable people.