The European Union’s drug regulator expressed doubts about whether a second booster dose of the currently available COVID-19 vaccines would be a sustainable long-term approach. Marco Cavaleri, the European Medicines Agency’s (EMA) head of vaccines strategy, told a media briefing, “There is an emergency discussion around the possibility of giving a second booster dose with the same vaccine currently in use. Data has not yet been generated to support this approach.” “We have not yet seen data with respect to a fourth dose,” he also said later. “We would like to see this data before we can make any recommendation, but at the same time we are rather concerned about a strategy that [involves] repeated vaccinations within a short term.” Cavaleri said an additional booster shot “could be considered as part of a contingency plan,” but “repeated vaccinations within short intervals will not represent a sustainable long term strategy.” Concerns Over Immune Response When asked to expand on his …