ROCHESTER, Minn. — There's no easy way to say this.

When it finally arrives, the long-awaited roll-out of COVID-19 vaccines is unlikely to mean the immediate end of masks, social distancing, avoiding crowds or any of the other pandemic-related adjustments that have put life as we know it on hold.

Though most Americans have weathered the past eight months with the thought that all this ends with a vaccine, it's becoming clear that the shots (there will be series of two of them) will still need to prove themselves over a period of many months.

"None of the trials currently underway are designed to detect a reduction in any serious outcome such as hospital admissions, use of intensive care, or deaths," as researchers wrote last week in the journal BMJ. "Nor are the vaccines being studied to determine whether they can interrupt transmission of the virus."

That last part bears repeating. The COVID-19 trials now seeking a so-called Emergency Use Authorization (EUA) are not even designed to prove the vaccines protect a person from getting COVID-19. Like the recipients of the flu vaccine, the newly COVID-19-vaccinated will still face a risk of contracting the illness, they just will avoid mild symptoms, at least more than half of the time.

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"Hospital admissions and deaths from COVID-19 are simply too uncommon in the population being studied for an effective vaccine to demonstrate statistically significant differences in a trial of 30 000 people," the BMJ researchers explained. "The same is true of its ability to save lives or prevent transmission: the trials are not designed to find out."

For the time being, this is all allowable in the eyes of regulators.

"We have not specified any requirement or preference for a specific endpoint (proof-of-effectiveness) to be used in the primary analysis of vaccine effectiveness," FDA representative Doran Fink said in a virtual conference on the status of the trials last week. "Most of the studies underway are using disease of any severity as the primary endpoint to be analyzed."

In short, if a vaccine causes a person with COVID-19 to avoid mild symptoms such as cough or fever, that patient can be recorded in a column tabulating success.

As a result, "many questions of importance will remain after EUA or licensure," Stephanie Schrag of the CDC vaccine task force said at the same conference. "Policies for a vaccine known to prevent transmission," she said, "can look very different than policies for a vaccine that protects from severe disease but not transmission."

Widespread deployment of a weakly effective COVID vaccine could provide a false sense of security, Fink cautioned, diminishing "wearing of masks, use of PPE and social distancing."

The approval of a weak vaccine could delay the development of better vaccines, he added. Green-lighting a weak vaccine could even open the door to even weaker vaccines, thanks to a bargain-basement regulatory threshold known as a "criteria of noninferiority."

Like the FDA and CDC, the Minnesota Department of Health remains bullish on the approach of new vaccines, regardless.

“Certainly, Minnesotans should expect any vaccine to be safe and effective, but it’s also important to ensure they understand its limitations," state health officials offered in a statement. "Though medical professionals do not attempt to promote the flu vaccine as an absolute shield from contracting the flu, we know that the vaccine prevents huge numbers of hospitalizations and death."

MDH says it will not lower its standards for a COVID-19 vaccine, and that it will rely on recommendations from the Advisory Committee on Immunization Practices, an independent review organization.

Contacted for an interview, a top vaccine authority in the state expressed her confidence that the prevention of mild symptoms is an acceptable standard for the worst outcomes from COVID-19.

Lynn Bahta, Immunization Clinical Consultant at the Minnesota Department of Health. Submiotted photo.
Lynn Bahta, Immunization Clinical Consultant at the Minnesota Department of Health. Submiotted photo.

"You can't end up in the hospital," said Lynn Bahta, immunization clinical consultant at MDH, "if you don't have symptoms of COVID."

Of course, COVID-19 routinely defies our assumptions about its progression of illness. The evidence base for new drugs, moreover, is filled with examples where improvements in lesser benchmarks failed to translate into the hard outcomes that matter — such as fewer hospitalizations and death.

That said, the news of one more moving of the goalposts with COVID-19 seems par for the course with our "just-in-time" global pandemic learning curve. With so much upended and the solutions unwritten, the public seems to have absorbed just as can be handled, and no more.

"In the ideal world, we want a vaccine like the measles vaccine," Bahta said, "where one shot protects a person. But it's important that as people get a vaccine, we understand what the data do and don't tell us.

"You're still going to need to mask, to distance as much as possible, to take preventive measures like washing your hands and avoiding touching your face ... We will know we can start backing off when we are able to see the amount of disease going down, hospitalizations and deaths dropping dramatically. But we have to get enough people vaccinated for those data to show up."