London, Sep 21 : Another 36,100 people in Britain have tested positive for Covid-19, bringing the total number of coronavirus cases in the country to 7,465,448, according to official figures released on Monday. The country also recorded another 49 coronavirus-related deaths, Xinhua news agency reported. The total number of coronavirus-related deaths in the UK now stands at 135,252. These figures only include the deaths of people who died within 28 days of their first positive test. The latest data came as a trial of what has been described as the world's first multi-variant vaccine booster against Covid-19 kicked off in the British city of Manchester on Monday. A married couple, both in their 60s, became the first participants in the trial, a collaboration between the University of Manchester and a National Health Service (NHS) foundation trust in the city. Launched by US pharmaceutical company Gritstone, the drug, called GRT-R910, is claimed to boost the immune response of first-generation Covid-19 vaccines to a wide array of variants of Sars-Cov-2, which cause Covid-19. The phase one trial of the vaccine is taking place at the National Institute for Health Research Manchester Clinical Research Facility at Manchester Royal Infirmary. A spokesman for the University of Manchester said data evaluating the vaccine is expected in the first quarter of 2022, with results from the pre-clinical studies published later in the year. Meanwhile, the vaccine programme has been stepped up with booster invites being sent out to vulnerable Britons while 12 to 15-year-olds also starting to receive their first jabs. Those aged 12 to 15 are being offered vaccines at some schools in England from Monday and the rollout is also beginning in Scotland and Wales this week. More than 89 per cent of people aged 16 and over in the UK have had their first dose of vaccine and more than 81 per cent have received both doses, the latest figures showed. To bring life back to normal, countries such as the UK, China, Germany, Russia and the US have been racing against time to roll out coronavirus vaccines. /IANS