As Covid-19 vaccines are rolled out across the world, a growing band of recipients are complaining of being flattened by side effects, especially after a second dose. Recipients describe symptoms from fever to fatigue that are more profound than the jolt some get from a seasonal flu shot. Although the post-vaccination malaise is generally innocuous and fades after a day or two, some hospitals and medical centers are staggering immunizations of health workers to avoid a brief cluster of absenteei