A Covid-19 vaccine, amazingly, is close. Why am I so worried?

A mere six months after identifying the SARS-CoV-2 virus as the cause of Covid-19, scientists are on the precipice of a having a vaccine to fight it. Moderna and the National Institutes of Health recently announced the start of a Phase 3 clinical trial, joining several others in a constructive rivalry that could save millions of lives.

It’s a truly impressive a feat and a testament to the power of basic and applied medical sciences. Under normal circumstances, vaccine approvals are measured in decades. Milestones that once took months or years have been achieved in days or weeks. If these efforts are successful, the Covid-19 vaccine could take a place alongside the Apollo missions as one of history’s greatest scientific achievements.

I’m optimistic. And yet, as someone who studies drug development, I want to temper expectations with a dose of realism and perhaps a bit of angst. Behind the proud declarations, many science and medical professionals have been whispering concerns. These whispers have escalated into a murmur. It’s time to cry them loudly:

Hey, Food and Drug Administration: Don’t be rash! Premature approval of a sub-standard Covid-19 vaccine could have dire implications, and not just for this pandemic. It could harm public health for years, if not generations, to come.

Unfortunately, elements now in place make such a disastrous outcome not only possible but in fact quite likely. Specifically, the FDA and its staff of chronically overworked and underappreciated regulators will face enormous public and political pressure to approve a vaccine. Whether or not one worries about an “October surprise” aimed at the upcoming election, regulators will be pressed hard. Some will stand firm. Some may resign in protest. But others could break and allow a bad vaccine to be released.

What makes a “bad vaccine”? Insufficient protection against the disease it is designed for, unwanted side effects, or some combination of the two. If an approved Covid-19 vaccine turns out to be ineffective, this could unintentionally promote wider spread of the disease by individuals who presume they were protected from it. Likewise, a negative experience with one vaccine might discourage the use of other vaccines that are far more safe and effective, whether they are for Covid-19 or other vaccine-preventable diseases.

Some things take time. Under normal circumstances, ensuring that a vaccine’s effects are safe and durable requires years of study and monitoring. And there is some evidence that natural immune responses to SARS-CoV-2 infection could be transient, making sustained investigation all the more necessary. A merely short-term effect could encourage vaccinated individuals to resume risky behaviors, which would all but guarantee that the epidemic endures. And if unintended side effects turn out to include, for instance, chronic inflammatory or autoimmune disease, a bad vaccine could impart lifelong damage.

But wait, there’s worse! A bad Covid-19 vaccine could further undermine confidence in the many safe, reliable vaccines already in our public health arsenal. Vaccine skepticism and anti-science bias, propagated by B-list celebrities and Russian troll farms, have been gaining strength all year. Combined with disappointing Covid-19 outcomes, such malign forces could facilitate the reemergence of once-vanquished foes — polio, measles, mumps, rubella, diphtheria, whooping cough, and tetanus — that once killed multitudes of children each year.

These are enormous risks. Placing all of our bets on a small set of untried vaccine technologies would be gobsmackingly foolish. Yet this is exactly what we are now doing. Most of the high-profile names capturing headlines are pursuing comparatively minor variations on a theme of genetic vaccines (those delivered via DNA or RNA). If one approach happens to work, the odds are higher the others will work as well. Disappointing results from one candidate, though, might presage failure across the board.

Rather than investing in a balanced portfolio of vaccines with different approaches — not to mention different therapies, devices, and diagnostics for treating Covid-19 — too many observers, too many companies, and too many governmental officials seem to be narrowly focused on hopes for a “savior” vaccine. Were that savior to fail, our national morale, already low, could plummet even further.

Don’t get me wrong. I, along with millions of Americans, want a Covid-19 vaccine. But we deserve one that’s been proven to be safe and effective.

It’s not too late to take a deep breath and devise a strategy to balance short- and long-term goals, including vaccination, improved diagnostics, and existing and novel treatments. We must support the FDA and hope that its scientists and physicians retain the strength and conviction to resist approving a substandard vaccine.

For encouragement, we should look to Frances Oldham Kelsey, a veritable patron saint of the FDA. In 1960, during her first month working for the agency, Kelsey was asked to approve a sedative called Kevadon, which had the potential to generate billions in revenue. Despite enormous pressure, Kelsey spotted a risk for toxicity and dug in her heels. She refused to rubber stamp the approval. Her actions saved the lives of countless babies. Kevadon, better known as thalidomide, proved to be one of the most dangerous and disfiguring drugs in history.

Kelsey passed away in 2015 at the age of 101. We must pray that her spirit inspires a new generation of FDA leaders with the courage to say, “No.”

Michael S. Kinch is associate vice chancellor, professor of biochemistry and molecular biophysics, and director of the Centers for Research Innovation in Biotechnology and Drug Discovery at Washington University in St. Louis. He is the author of “Between Hope and Fear: A History of Vaccines and Human Immunity” (Pegasus Books, 2018) and two other books.