LONDON, Nov 5 (Reuters) - The prevalence of COVID-19 infections in England remained at around 1 in 50 people in the week ending Oct 30, a school half-term break, Britain"s Office for National Statistics said on Friday, steadying at its highest level of the year. The ONS said that prevalence was unchanged from the previous week, after five straight weeks of rising infections. The ONS said that the trend was "uncertain" in the latest week, after infections had been on the rise leading up to the half term break, which for most schools started on Oct 25. The reproduction "R" number in England also turned lower and could be below 1 - another piece of evidence that a recent dip in daily reported cases could be due to a shrinking pandemic and not just trends in testing during the holiday. Prime Minister Boris Johnson has resisted calls to move to Plan B, involving mask mandates, vaccine passes and work from home orders, and is leaning on booster vaccinations and shots for children to avoid lockdown this winter. However, prevalence remains at high levels as students return to school. Britain is averaging 40,000 new cases each day and has reported 141,000 deaths from COVID. Infection rates decreased for older, senior school children over the week, the ONS said, dipping to 7.5% from 9.1% the previous week, but prevalence remained the highest in those children.Paul Hunter, Professor in Medicine at the University of East Anglia, said that estimated prevalence started falling a bit before schools broke up for half-term. "(This) would give hope that cases in this age group may not start to increase again now that schools are back," he said. "We will have to wait another one or possibly two weeks before we can be certain." The region with the highest prevalence was the South West, with 2.9% estimated to be infected, echoing the findings of an Imperial College London survey released on Thursday. read more The region was impacted by an error at a private lab that resulted in an estimated 43,000 people wrongly being given negative PCR test results. read more On projections published on Friday, pandemic modellers said that the error at a private lab had created difficulties. "As a result (of the issue), the recent trajectory of the epidemic is less clear and the uncertainty around SPI-M-O"s medium-term projections is larger than usual," advisers in the government pandemic modelling subgroup said.