Covid infection cases are “rising exponentially” across England in the younger and mostly unvaccinated age groups, according to scientists. A study commissioned by the Government found that infections have increased by 50 per cent between 3 May and 7 June, which coincided with the rise of the Delta Covid variant. Experts from Imperial College London said their findings show a “rapid switch” between the Alpha variant - which first appeared in the UK in September 2020 - and the Delta variant in the last few weeks, with the latter accounting for up to 90 per cent of all coronavirus cases. 'Prevalence is increasing exponentially and it is being driven by younger ages' The research - which has been published as a pre-print on an online server - shows the bulk of infections is being driven by children aged between five and 12, as well as younger adults aged between 18 and 24. Infections in these age groups are around five times higher when compared to those over 65, the researchers said. Data showed that the “weakened link” between infection rates and hospital admissions was “well maintained” for those aged 65 and above, while “the trends converged below the age of 65 years”. The scientists said their findings from the React study suggest that imminent expansion of the vaccine programme to those aged 18 and above “should help substantially to reduce the overall growth of the epidemic”. Stephen Riley, professor of infectious disease dynamics at Imperial and one of the study authors, said: “Prevalence is increasing exponentially and it is being driven by younger ages. “And it appears to be doubling every 11 days. “Clearly that is bad news… but the key thing to point out here is that we are in a very different part of the epidemic in the UK and it is very difficult to predict the duration of the exponential phase.” Study author Paul Elliott director of the React programme and chair in epidemiology and public health medicine at Imperial, said: “I think we can take quite a lot of comfort from the fact that when we look in the details, it does appear that there is very, very good protection in the older ages, where there is virtually everyone double vaccinated. “And in the younger group under the age of 65, where a much smaller proportion have been vaccinated or double vaccinated, most infections are occurring in the unvaccinated group. “And the Government has clearly announced that they want to vaccinate all adults in the period between now and July 19, I think that will make a very big difference and increase the total amount of population immunity.”