Governments around the world are debating the timeline for offering Covid-19 vaccines to the public, as drugmakers speed up development. WSJ’s Daniela Hernandez explains the potential health risks linked to fast-tracking vaccines. Photo: Siphiwe Sibeko/AP Europe’s fight to contain a second wave of the coronavirus has reached a tipping point. Months after authorities flattened the curve of coronavirus infections across Europe by imposing some of the Western world’s toughest restrictions on millions of people, the virus has crept back onto the Continent. Hospitals are filling up. Bars and cafes are closing down. This…