Exactly five years ago today, after more than 118,000 cases and more than 4,200 deaths across 114 countries had been recorded, the World Health Organization declared the novel coronavirus a pandemic.

With the virus spreading rapidly around the world, the need for a vaccine was desperate — but the prior record for the fastest development of a new vaccine to a new virus was four years Yet vaccines using the new technology of mRNA were developed by Moderna and Pfizer/BioNTech in a matter of months, and were already being put into arms by the first anniversary of the pandemic.

Rather than containing a weakened or dead virus, as most vaccines do, the shots contained mRNA — or messenger RNA, a kind of genetic script — that prompted cells to produce special proteins that would allow the body to develop an immunity to the novel coronavirus.

While new Covid variants would later pose challenges in the pandemic, scholars at the Commonwealth Fund, a health policy research group, estimated that the Covid vaccines prevented more than 3 million deaths in the United States alone and 18 million hospitalizations from December 2020 to November 2022.

Scientists, who are usually not prone to crediting divine intervention, called the mRNA vaccines a miracle. Four in five Americans received at least one dose; when we remember less than half of Americans get their flu shot each year, the high uptake of mRNA shots, at least initially, signaled a willingness from the US public to trust this novel technology. After most Americans received their shots, more people returned to work, more kids went back to school, and the economy began to rebound. And there was optimism that mRNA technology could be used to make better vaccines for other diseases.

But even as the vaccines were actively pulling the US out of the pandemic, skepticism about mRNA technology was rising. Robert F. Kennedy Jr., still a private citizen at the time and one of the country’s most vocal vaccine skeptics, urged the first Trump administration to pull the shots.

Now the nation’s top health official, Kennedy is reevaluating the US Health and Human Services’s contract with Moderna, which is developing flu vaccines targeting strains with high pandemic potential including the H5N1 bird flu that is currently

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