As the weather cools, the number of infections of the Covid-19 pandemic are rising sharply. Hamstrung by pandemic fatigue, economic constraints, and political discord, public health officials have struggled to control the surging pandemic. But now, a rush of interim analyses from pharmaceutical companies Moderna and Pfizer/BioNTech have spurred optimism that a novel type of vaccine made from messenger RNA, known as mRNA, can offer high levels of protection by preventing Covid-19 among people who are vaccinated.

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