The share of job listings that require new hires to be vaccinated against COVID-19 doubled in the first week of August to around 1,200, according to Indeed economist AnnElizabeth Konkel. “While the number of postings requiring a vaccine is still low, it’s a trend that’s really taking off,” Ms. Konkel said. “I think a growing number of employers are trying to keep workers safe and do not want to shut down again this winter. … They see vaccines as the way out of this pandemic.”