Drew Holden is a public affairs consultant in D.C. and a former Republican congressional staff member.

In response to a slight uptick in local cases, D.C. Mayor Muriel E. Bowser (D) announced that the city would reinstate indoor mask mandates even for the vaccinated.

There are many reasons to resist this change. Bowser’s step backward comes despite the city having only three deaths from the coronavirus in the past two weeks and with a positive test rate hovering around 1 percent. Businesses, already wounded by the pandemic, again must make changes to accommodate a new rule. And a government that can tell people what they can and can’t wear and how to run a business with such minuscule data should give anyone pause, especially when the mayor herself isn’t interested in following it.

Even suspending disbelief about these important issues, the mask mandate for vaccinated people will undermine another, more critical public health issue: vaccines. Asking someone to don a mask inside may seem innocuous. But constantly changing the public health guidance — and doing so with such limited evidence — will make it harder to persuade hesitant Washingtonians to get vaccinated.

Indoor masking helps reduce transmission, but the best way to prevent more D.C. residents from dying of the coronavirus is to increase vaccination. Though 54 percent of adults citywide are vaccinated, rates in certain parts of D.C. are far lower. In Wards 7 and 8, both majority Black, only 30 percent and 25 percent of adults are vaccinated. D.C.’s Black and Hispanic residents were far more likely than their White neighbors to say they were skeptical of vaccines.

In D.C., the unvaccinated are overwhelmingly poor people of color. Coronavirus vaccine hesitancy isn’t dissimilar from long-standing vaccine hesitancy more broadly among people of color, driven by government malpractice like horrid syphilis experiments conducted on Black people at the Tuskegee Institute as recently as the 1970s.

But these individuals aren’t entirely shut off from the prospect of getting the vaccine.

As time has passed, coronavirus vaccine resistance has eroded — slowly — for Black adults in the District. The best message is to reiterate, again and again, that the vaccines are safe and effective and getting one makes it less likely that someone will be killed by the coronavirus than be struck by lightning.

Mandating masks even for the vaccinated sends a clear (if unintended) message to the contrary: Even when you have the vaccine, you aren’t really safe to yourself or others, even if we just told you the opposite was true. How can those already deservedly distrustful of the medical wisdom of the government overcome their skepticism if the government itself can’t seem to get the story straight?

By reimposing the mask mandate for the vaccinated, Bowser has also eliminated one of the more obvious and effective incentives for those otherwise resistant to the vaccine. Polls have shown that escaping masking requirements has been a strong incentive for people to get vaccinated. Even when they sound silly, incentives work. In Ohio, a state-run lottery led to a spike in vaccinations when residents were more skeptical of the vaccine than they are today.

Other states — even those with more coronavirus deaths — aren’t taking similar steps. Neighboring Virginia and Maryland haven’t done so, even as cases have similarly increased slightly. Even densely populated New York City has so far resisted a new mask mandate.

We must remember that this new guidance doesn’t come in a vacuum. Americans have grown increasingly distrustful of public health guidance as the pandemic has worn on. Though some of this undoubtedly has been the result of bad actors profiting off skepticism, the messaging blunders and changing guidelines from the Centers for Disease Control and Prevention and other institutions have also undermined trust. In an evolving situation like the pandemic, public health needs to evolve with new information. But changing D.C.’s guidance when the seven-day average for coronavirus deaths has been above zero only one day in the past month and when existing vaccines are highly effective against the latest strain of the virus risks driving down that confidence even further.

Facing the public health challenges that could still lie ahead will require not just wise guidance but also a belief among the American people that those decisions aren’t capricious or unreasonable. All the best science won’t make a difference if the public’s ears are shut to it.

Public trust is particularly important as the United States hopes to roll out vaccines for kids under 12 this year. Overcoming parental skepticism to a novel vaccine is already a tall task. A lack of public confidence could make it near impossible.

The past 18 months have been a case study in the ways that even well-intentioned policies can have tragic consequences. To many, it may seem like a minor imposition to ask people to put on a mask to keep their neighbors safe. But even the pro-mask camp should be wary of the unintended consequences that could endanger, rather than protect, D.C. residents.