Jerome Adams was U.S. surgeon general during the Trump administration. He is a University of Virginia Darden dean’s fellow.

I know what it’s like to be well-intentioned but wrong on masking. Last year, based on Centers for Disease Control and Prevention and World Health Organization recommendations and limited knowledge about asymptomatic spread, I initially said masks were not effective in preventing the general public from catching coronavirus. After realizing you’ve erred, the best way forward is to own the situation and hit the reset button. That’s what I did — and that’s what the CDC needs to do, too.

The agency urgently needs to revise its guidance on masking to combat the rapid growth in covid-19 infections driven by the delta variant.

When the CDC changed its guidance on masking in May, many Americans were excited and relieved. The announcement surprised state and local health officials throughout the country but was based on data showing that the coronavirus vaccines were highly effective at preventing death and severe disease, as well as inhibiting transmission of the virus. If vaccinated, this thinking held, people no longer needed to wear a mask in most public settings.

Many doctors and others decried the revised guidance as too big of a move, too soon. I was among those who initially thought that the revised guidance might encourage more people to get vaccinated. After all, they could enjoy more pre-pandemic freedoms at lower risk. But things have not worked out as I and other public health experts had hoped.

In hindsight, it’s clear that the message many Americans heard was that, vaccinated or not, masks were gone for good. Without a mechanism to determine who is vaccinated and who is not, businesses and others have been helpless to determine which people were following the guidance — that is, vaccinated and safely unmasked — and which people were simply taking the opportunity to eschew a highly politicized (and widely loathed) public health intervention.

As more unmasked people began to be seen in public settings than statistics suggested had been vaccinated, other factors combined to create the risky situation our country now faces. More than a year into the pandemic, populations tired of lockdowns were ready for summer escapes — returning to travel, amusement parks, camps, sporting events and other gatherings. While the coronavirus vaccines — crafted in record-breaking time — had proved highly effective, the delta variant is much more contagious than the covid strain that broke out last year. The delta variant is responsible for 83 percent of new covid cases in the United States, up from 51 percent the week of July 3. It is responsible for 99 percent of recent deaths in U.S. covid cases (nearly all of which are among the unvaccinated).

Now, vaccination is far and away the best tool to fight covid. The vaccines so far remain highly effective at preventing severe disease and death, even among those infected with delta. But vaccination levels are still far below what’s needed for herd immunity in many places throughout the United States. And with many communities — particularly communities of color — at risk for yet another devastating wave of cases, hospitalizations and deaths, masks are the next best tool that officials have in places where vaccination levels remain low despite covid cases rapidly rising.

As is clear from the experience in Los Angeles County, which recently began requiring even vaccinated individuals to wear masks indoors again as covid cases reached levels not seen since March, it is difficult to bring back mask mandates when the perceived message from the CDC is that masks are needed only for the unvaccinated.

No one wants a return to the fear, pain and isolation of last year’s shutdowns. But short of lockdowns (or the “let ’er rip” approach to risking infection that endangers countless lives, including our still largely unvaccinated youth population), we have two primary options: vaccinations and masking. We must work hard to increase vaccinations while simultaneously preparing the public for masking. The CDC could help by acknowledging that its prior messaging has not been effective and actually harmful. Instead of vax it or mask it, people might need to vax it and mask it.

The pandemic situation has changed from what it was in the spring. Given the rapid increase in covid cases driven by the delta variant, the CDC urgently needs to revise its guidance to vaccinate and mask in places where cases are rising yet vaccination rates remain low. Such conditions won’t last forever, but as we weather the challenges of the delta variant, masks need to be a viable option in public health officials’ tool kit until vaccination rates reach a sufficient level.