More covid-19 vaccines pass clinical trials

THE STORY of the past year has been one of fear and hope. Covid-19 has killed 2.2m people around the world. But never have scientists created effective vaccines so quickly. In recent months, however, worrying mutations of the virus have emerged in different parts of the world. The results from clinical trials of two new vaccines, announced in the space of 24 hours this week, are encouraging, but also show that those new variants will make vaccinating the world a lot more complicated than expected.Novavax, an American firm, tested its vaccine in Britain and South Africa, where two of the variants have emerged. The company announced its results on January 28th. In the British trial, the Novavax vaccine was nearly 90% effective against symptomatic covid-19 when given in two doses 21 days apart. In South Africa, however, the same regimen was only 60% effective (and down to 49% when people with HIV were included)—though these figures are still preliminary and may change.