The Joint Committee on Vaccination and Immunisation (JCVI) announced this week that everyone in the UK aged 16 and 17 should be offered the Covid-19 vaccine. Just two weeks ago, it said the vaccine wouldn’t be offered to non-vulnerable people aged 12-17. The change in position is welcome, but the reasons for the committee’s two-week delay, and its decision to not extend the vaccine to 12- 15-year-olds, are unclear. Unlike the US Centers for Disease Control (CDC), the committee has offered no quantitative analysis of the risks associated with vaccinating people in this younger age group. Delaying the rollout of the vaccine to adolescents is risky. Recent figures show that 1% of 10-19s were being diagnosed with Covid-19 a week. Waiting for further data on vaccine safety when infections are ripping through younger age groups isn’t cautious, it’s reckless. This seems particularly clear given what we already know about the safety of vaccines in adolescents. The UK Medicines Healthcare Products and Regulatory Authority deemed the Pfizer vaccine safe and effective for 16- and 17-year-olds in December 2020, and stated that “the benefits of this vaccine outweigh any risk” when approving it for 12- to 15-year-olds in June this year. In the US, where close to 9 million adolescents aged 12 to 17 have been fully vaccinated, the CDC has unambiguously recommended vaccines for those 12 and above. Worryingly, the JCVI’s recent announcement has only recommended the first dose of the vaccine for 16- to 17-year-olds. Millions of adolescents in this age group have been vaccinated with two doses in the US and other countries, and we know that full protection with the Delta variant depends critically on receiving two jabs. So much data on this is already available. It’s unclear why the JCVI needs yet more data to make an assessment that many countries made months ago. The choice in the UK now is between infection and vaccination. Given the high rates of infection among young people in the UK, there is little doubt that the benefits of vaccines far outweigh the risks. Vaccines also reduce the burden of long Covid by protecting people against infection. The Office for National Statistics, which has regularly followed up with thousands of people across the UK who have had Covid-19, finds that persistent illness is common (about 8%) after infection among children. For many of those who become infected, Covid-19 is not a minor illness. Recent ONS estimates suggest that around 20,000 children aged under 17 with long Covid currently suffer from its impact on their day-to-day lives. Some 7,000 children have been living with this for more than a year. Although only a few children may develop severe symptoms as a result of Covid-19, if thousands of children are infected the number who become seriously ill can quickly stack up. It’s puzzling that those who are nervous about vaccinating children due to the risks of extremely rare and typically minor side-effects are not equally concerned about exposing children to a novel virus. We know that Covid-19 causes poorly understood multi-system, long-term disease, even in young adults with mild infection, and is associated with thinning of brain grey matter. We also know it causes long-term neurological effects among hospitalised children, some of which may be permanent. High rates of infection among adolescents and younger people reflect the spread of the Delta variant, particularly in schools, where few safety measures have been put in place. Vaccinating adolescents could have a significant impact on reducing transmission in schools and reduce the educational disruption that children have suffered over the past 18 months. Reports from frontline clinicians across the globe suggest that more children are being seen in hospitals as a result of Delta, and that more are requiring intensive care support. While the JCVI has dithered about whether 16- to 17-year-olds should receive the vaccine, and has yet to make a decision on whether 12- to 15-year-olds should get the jab or whether 16- to 17-year-olds should get a second shot, millions of 12- 15-year-olds have been vaccinated across the US, Europe, Israel and south-east Asia. During this period thousands of children have been infected in the UK, a significant number of whom will develop longer-term illness, much of which could have been prevented. Waiting on the JCVI to decide will come at a cost to children and their families. Delaying the vaccines gives out mixed messaging, which could contribute to vaccine hesitancy. If parents and children are only offered a vaccine only months down the line, they may well ask whether it’s worth having. Over the last year, the government has normalised the mass suffering and death of adults. Just because the risks of Covid-19 appear lower in children, we must not normalise their long-term illness. Vaccines are a crucial step towards protecting adolescents from these risks. Dr Deepti Gurdasani is a clinical epidemiologist and senior lecturer in machine learning at Queen Mary University of London