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 driving fears of another pandemic.
With Kennedy at the helm of HHS, scientists and public health experts worry that a major breakthrough in medicine development may now backslide. mRNA technology has shown the potential to deliver new cancer treatments and a universal flu vaccine, and could lead scientists to uncover even more applications. But now, mRNA vaccine development is in peril — just a few years after proving its value.
Why so many Americans turned against a vaccine miracle
Scientists had been trying since the 1990s to crack mRNA vaccines, but progress was slow, in part because it was difficult to secure funding. But when the Covid-19 pandemic hit, Operation Warp Speed funded rapid clinical trials, expanded manufacturing capabilities, and offered huge purchase guarantees for companies that delivered an effective vaccine.
mRNA vaccine development proved almost too good to be true during a real-life emergency. During the new Covid vaccines’ early clinical trials, they showed a 90 percent efficacy in preventing any symptoms at all.
In the real world, the efficacy of early vaccines didn’t quite live up to that hype. The Moderna and Pfizer shots were still very effective in preventing severe disease, but some vaccinated people did get infected. Many people reported experiencing unpleasant side effects like fatigue or body aches after their shot; some of them felt ill enough to miss work. And as more variants of the disease emerged and as protection that many people got from the vaccines faded over time, shots became less and less effective.
For such purely biological reasons, there were some important caveats to the “miracle” that public health experts were touting. But those side effects fed into existing anti-vaccine sentiment, and many people — activated by influencers and politicians who portrayed business closures and mask requirements as authoritarian measures of control — began to turn against the Covid vaccines. By autumn 2021, less than a year after the vaccines’ debut, anti-vaccine communities were thriving, constructing an alternative narrative of the pandemic in which the disease itself was not actually that serious but the vaccine could alter your DNA or plant a chip in your body.
Public embrace for the vaccine shattered and never recovered. Data from the CDC speaks for itself: Uptake for the booster shots that succeeded the original mRNA shots has plummeted; in November 2023, only 15 percent of Americans received the latest version of the vaccines.
The low rates for Covid-19 boosters underscored growing misinformation: Four in 10 Republicans said in a January 2025 KFF poll that it was “probably” or “definitely” true that more people had died from the Covid-19 vaccines than from Covid-19 itself, which represented a 15-point increase from a July 2023 survey.
Shifts in the national political mood have only entrenched this skepticism further. In December 2021, Kennedy said the Covid shots were “the deadliest vaccine ever made.” (Scientists have documented at most a few dozen deaths attributable to the vaccines worldwide after billions of doses were administered, and population-level analyses have detected no meaningful increase in mortality after the vaccines were introduced.) By February 2025, Vice President JD Vance was echoing some of those claims. “I took the vax, and, you know, I haven’t been boosted or anything,” Vance told podcaster Joe Rogan. “But the moment where I really started to get red-pilled on the whole vax thing was when the sickest that I have been in the last 15 years by far was when I took the vaccine.”
Elon Musk, meanwhile, has emerged as something of a double agent, simultaneously embracing skepticism of the Covid-19 vaccine development while underscoring the risk of discrediting mRNA technology entirely.
Musk claimed on his own platform X that he “almost went to hospital” after a Covid booster, before adding: “That said, synthetic mRNA has a lot of potential to cure cancer and other diseases. Research should continue.”
He’s right. As Covid-19 has upended our politics and culture so thoroughly in the past five years, we are at risk of losing out on important medical innovations. That cure for cancer may never materialize if governments stop offering financial support or ban mRNA use, or if people simply don’t trust it and won’t take it because they’ve become convinced by these conspiracies.
But all of those things are unfolding at once.
The US health department’s recent decision to reevaluate a $600 million contract with Moderna to develop a shot that targets flu strains with particularly high pandemic potential has terrified public health experts. With H5N1 already percolating as a pandemic threat, former federal health officials have warned the decision could hamper our ability to quickly produce a new vaccine whenever the next influenza pandemic strikes — be it bird flu or something else.
At the state level, Republican leaders, including Florida Gov. Ron DeSantis, have called for a ban on any vaccine mandates involving mRNA shots. Some state lawmakers want to press further, banning all mRNA vaccines for the people they represent. No such ban has yet become law but in the last year alone, legislation has been introduced in Idaho, Iowa, and Montana.
“I believe all the gene therapy products that are being used for immunization should be put on hold until we can determine their safety and efficacy,” said Idaho Republican Sen. Brandon Shippy. (The mRNA vaccines do not alter your genes, as gene therapies made specifically for genetic disorders like sickle cell disease are designed to do.)
Many Republican voters not only believe the Covid-19 vaccines killed more people than Covid did, but they’re souring on other parts of the public health consensus, including long-held recommendations for childhood vaccines.
In a November 2024 paper, researchers looked at worldwide attitudes toward mRNA technology and discovered “widespread negative sentiment and a global lack of confidence in the safety, effectiveness, and trustworthiness of mRNA vaccines and therapeutics.”
For now, mRNA development in the US and around the world continues. Scientists are working on a universal flu shot and respiratory virus vaccines. They are showing promising results with cancer vaccines, including for diseases such as pancreatic cancer that have resisted older treatments. Major pharmaceutical firms believe that mRNA could be harnessed to treat rare genetic disorders, too.
Covid showed that the science behind mRNA technology works. The opportunity for major medical breakthroughs still exists. The question now after our collective experiences of the past five years, is whether we still want them.
