Each Covid-19 milestone is a reminder of the losses and suffering the world has endured. The death toll from the pandemic passed 4 million last Wednesday, buoyed by a resurgence of the disease as a result of the more infectious, and perhaps dangerous, Delta variant. Among countries struggling with the strain are India, Indonesia and Bangladesh, while fresh outbreaks in which it accounts for most cases have occurred in Britain, South Korea and Australia . With the virus outpacing vaccination in many places, the crisis is far from over. Three countries, the United States, Brazil and India, account for more than a third of the deaths. The US, with more than any other nation at 15 per cent of the total, now has a falling number due to widespread vaccination. But in countries where there has been a reluctance to get jabs or distribution has been limited, fresh waves of the virus threaten. Indonesia, now in second place for daily infections behind India, has a particularly worrying problem; its health care system is struggling to cope due to a lack of beds, insufficient supplies of oxygen and large numbers of hospital staff falling ill or dying, despite being immunised. Studies have shown that the Delta variant makes vaccines less effective; Israel’s health ministry announced last week that the effectiveness of the Pfizer-BioNTech jab was 64 per cent against all coronavirus strains, down from 95 per cent in May. Health authorities in Singapore have decided that the Chinese-made Sinovac vaccine, available privately in the city state since it was given emergency approval by the World Health Organization last month, would not be included in immunisation counts as there was insufficient efficacy data, particularly against the Delta strain. Hong Kong offers both shots for free. The Delta strain is behind the tightening of social-distancing rules in South Korea, and a new state of emergency in Tokyo, which is hosting the Summer Olympic Games later this month without spectators. Governments prematurely relaxing restrictions need to reconsider their decision as the new variants spread. Vaccination still holds the key; production has to be boosted, distribution made more equitable and vaccine hesitancy tackled.