Last week, the World Health Organization (WHO) recommended that even those vaccinated for Covid-19 continue to wear masks and take all of the other precautions to stop community transmission. “People cannot feel safe just because they had the two doses. They still need to protect themselves,” WHO Assistant Director-General Dr. Mariangela Simao said during a media briefing.

This contradicts the recommendations of the US Centers for Disease Control and Prevention (CDC), which says fully vaccinated people can go without masks unless local rules instruct otherwise. CDC Director Rochelle Walensky addressed the “confusion” on Wednesday, saying her agency was sticking by its guidelines.

“Less than 15 percent around the world have been vaccinated, and many… of those have only received one dose of a two-dose vaccine,” she said. “As the WHO makes those recommendations, they do so in that context.”

People in the US are fortunate to have an abundance of working vaccines, while two-thirds of adults have received at least one shot, so the situation is different, Walensky said. But local policymakers should base their decisions on the local circumstances, she added, referring to places in the US where the authorities go against the CDC guidelines.

Los Angeles County is notable for asking on Monday that all people continue to wear masks in public indoor spaces regardless of their vaccination status. The recommendation cited the spread of the more-transmittable Delta variant, which now accounts for half of all Covid-19 cases in LA, as the reason.

Walensky said the two two-shot vaccines used in the US have proven to be effective against the Delta variant. Data for the single-shot Johnson & Johnson vaccine has not been gathered yet, but the expectation is that it has also been effective.

She refrained from making a statement for or against taking a booster shot of a different vaccine after receiving the J&J vaccine, saying the CDC doesn’t have enough information yet to make a recommendation.

Amid the pandemic, mask mandates have become an integral part of the culture wars, with some people on the left using masks for virtue signaling and their opponents rejecting them as an affront to their personal freedom.

Some experts have warned that asking vaccinated people to wear masks as a precaution may do more harm than good. It signals that even vaccines offer no path to normalcy, and fuels public resentment against other health rules. This may backfire if, for example, a vaccine-dodging mutation of the virus arises and there is an urgent need to put all the restrictions back into place again.