It is inevitable that new Covid variants will continue to enter the country, scientists warned this weekend, claiming there are “obvious flaws” in the government’s system for reopening international travel to and from England. On Friday ministers decreed that some international travel could resume from 17 May, with travellers from England allowed to return from “green list” destinations without needing to quarantine. Portugal and Israel are on the list, along with South Georgia, the Faroe Islands and the Falklands. However, it is understood that members of the Scientific Advisory Group for Emergencies (Sage) are concerned that the government’s traffic light system amounts to “window dressing” and is not based on evidence about the risks of the spread of variants. These concerns are shared by other scientists such as Professor Martin Hibberd, of the London School of Hygiene and Tropical Medicine (LSHTM), who told the Observer that more testing was necessary before international travel should be allowed to reopen. With the current approach, it was inevitable that new variants would enter the country, he said. “While in the UK, we look forward to less disease and fewer restrictions, this is not the case in most of the world. Indeed, for many countries infections are likely to come in waves for at least another year and perhaps longer. As a result, imports are likely to become an increasingly important part of new transmissions circulating within the UK. We should develop an effective strategy to cope with the competing desires to allow international travel, while keeping circulating virus in the UK to a minimum. “From my infectious disease perspective, for travel, I would like to see more testing, preferably with professionally taken swabs, and more support for quarantining, at home when it is possible – and which can be verified for compliance – together with an effective tracing programme.” This point was backed by another LSHTM expert, Martin McKee, professor of European public health. “If everyone from England going to Portugal was only mixing with people from Portugal, that would be one thing. But if you go to a Portuguese resort, it is likely you would be mixing with people from other places. “The criterion you should be looking at is not the infection rate and vaccination rate in the host country, but among the people who you’re likely to be mixing with. It’s an obvious flaw. And if you’re going to be transiting through any airport, you’re going to be mixing with people who are going to be coming from other places.” As a result, some health experts have called for holidays abroad to be subject to strict controls. Gurch Randhawa, professor of diversity in public health at the University of Bedfordshire, said people should only take holidays in the UK at present. “Permitting overseas holidays without universal quarantine measures for all countries is not a risk we should take,” he said. “Without strict measures we will have more Covid-19 deaths in the coming months because of imported variants, as vaccines have reduced efficacy against some of these different strains.” These warnings were made as travel firms hailed their best day for holiday sales in months. Tui, the UK’s largest holiday company, said it had seen a huge increase in bookings with 60% of all holidays sold on Friday being trips to Portugal. The firm added that new flights and extra holidays had been added for people who wanted to “get away as quickly as possible”. Similarly, Thomas Cook said holidays to Portugal had been its “number one seller” since the government made its announcement about foreign travel. In contrast to the warnings made by some UK scientists, Clive Dix – who recently stood down as interim head of the British vaccine taskforce – said he thought there would be “no circulating virus in the UK” by August. He told the Telegraph that the UK vaccination programme would “have probably protected the population from all the variants that are known” which meant that the country would be “safe over the coming winter”.