As England moves towards an anticipated “big bang” lifting of coronavirus restrictions on 19 July, a senior World Health Organization official has warned countries to lift their Covid-19 restrictions slowly so as “not to lose the gains that [they] have made”. The comments from the UN global health body’s head of emergencies, Mike Ryan, were not aimed directly at Boris Johnson’s much-trumpeted reopening. However, they will be interpreted as grist to the mill of those health experts who have been arguing that England is moving too fast at a time when infections are surging. Ryan did, however, address reactions to Johnson’s announcement earlier this week amid claims by some that the new policy appeared to be to allow new infections on top of vaccinations so that the country could reach herd immunity, saying he did not believe that was the intention. Ryan said the idea of letting people get infected with Covid-19 earlier rather than later was “epidemiological stupidity”. His comments came at a briefing where the WHO once again urged countries to share Covid-19 vaccines to protect health and care workers and elderly and vulnerable people in low-income countries before expanding vaccination programmes to children. Addressing the speed of countries’ plans to reopen, Ryan added that in particular countries with low Covid-19 vaccination rates, combined with the lifting of restrictions, threatened a “toxic mixture”. Ryan said this was a time for extreme caution, but added that each nation had to make its own decisions about what precautions to take against Covid-19 and the lifting of restrictions. He spoke as the WHO announced the “tragic milestone” of four million recorded Covid-19 fatalities on Wednesday, adding that the pandemic’s true toll was probably higher. WHO chief Tedros Adhanom Ghebreyesus announced that the landmark had been reached, 18 months after the outbreak began in China in December 2019. “The world is at a perilous point in this pandemic. We have just passed the tragic milestone of four million recorded Covid-19 deaths, which likely underestimates the overall toll,” Tedros told a press conference at WHO headquarters in Geneva. Earlier this week Ryan cautioned against a “premature rush” back to normality. “For a lot of the world this thing is only getting started,” Ryan said. “I’m very pleased for countries that are getting this under control. But please spare a thought for those living without vaccines. “All of the countries of the Americas, we still have nearly one million cases a week. It isn’t over. The same in Europe – in the European region, we have half a million cases a week. It’s not like this thing has gone away.” The issue of how, when and how quickly to end coronavirus restrictions around the world has become fraught amid resurgences linked to the more transmissible Delta variant and public weariness with lockdowns, mask-wearing and other sanitary measures. Also commenting on the 19 July reopening plans, William Hanage, a professor of the evolution and epidemiology of infectious disease at Harvard, suggested that uncertainty remained over the outcome of ending of most restrictions in England. “In some ways, the situation is quite simple,” he told the Guardian. “The cases are rocketing in a way that reflects the highly contagious nature of Delta. It is beginning to look like the major thing explaining its potency is that transmissibility, rather than immune evasion, leading to a lot of infection of and transmission between vaccinated individuals (although it certainly can happen, and reopening will offer the virus more opportunities). “This is going to produce a few things – first it will be hospitalisations and deaths, but far fewer than at the worst stage of the winter. This is certainly good news, or maybe better than the worst-case scenario. “On the other hand, with the reopening planned, there will be huge amounts of infection, and … a lot of people are going to feel pretty darned sick even if they don’t need a hospital bed. The long-term impacts are not known.” Some countries that have loosened restrictions on issues such as mask-wearing, like Israel, have been forced to backtrack. The Netherlands, too, lifted most lockdown measures on 26 June as cases were falling, and around two-thirds of the population has received at least one vaccination shot. However, with bars, restaurants, and nightclubs reopened, new cases in the country doubled to 8,000 in the week ending 6 July. On Wednesday health authorities reported 3,688 new cases for the previous 24-hour period. That has led the Dutch government on Wednesday to say it will consider whether it needs to take fresh action. “I think the sharp rise in infection numbers are a reason to request urgent advice from the outbreak management team”, the health minister, Hugo de Jonge, told reporters in The Hague.