The delta variant is the new pandemic scare story. Its spread into the United States hasn’t led to a surge in deaths or packed hospital wards, but the news of its existence rained on the Fourth of July parades.

Public health specialists have responded with a baffling spray of contradictory recommendations, conflicting information and seemingly inconsistent scientific facts. The result, as in earlier phases of the COVID-19 scourge, has been needless confusion and rage. Should vaccinated people wear masks? It depends whom you ask. Can economic life return to normal? Expert opinions vary.

Some say it depends on local conditions. Dr. Anthony Fauci, the White House medical adviser, says everyone should mask up in Alabama, which has a low vaccination rate and climbing cases.

Rochelle Walensky, director of the U.S. Centers for Disease Control and Prevention, recommended indoor masking for any community with a vaccination rate under a third. But Los Angeles County wants vaccinated people to wear masks despite a relatively high vaccination rate.

Delta, first detected in India, is even more transmissible than the super-transmissible variant now called alpha (previously B.1.1.7 and originating in the U.K.), which prompted calls for double masking just last spring.

The delta variant arose as a threat around the same time that public health authorities in the U.S. were encouraging individuals to make their own decisions about coronavirus safety instead of urging uniform standards of behavior. In May, the CDC relaxed its masking recommendations and Walensky declared that fully vaccinated people “can start doing the things” that they had stopped doing because of the pandemic.

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That shift was prompted by availability of highly effective vaccines, which appear to work against all forms of COVID-19, including the delta variant. But a shift to a focus on personal responsibility is also a political and ethical change. So it’s unsurprising, if also unsatisfying, that recommendations and rules vary: the World Health Organization joins Los Angeles County in saying that vaccinated people should wear a mask in most indoor settings, but the CDC maintains that mask decisions should be up to regions, businesses and individuals.

Walensky explained that vaccines are much more available in the U.S. than in most parts of the world and are more widely used in some U.S. states than others. So the CDC and WHO recommendations both can be said to have scientific support. But science also shows that vaccinated people are highly unlikely to get seriously ill even if infected by the delta variant, and are extremely unlikely to infect others in the grocery aisles.

That’s why “the science” isn’t, by itself, a prescription for sound public health policy. Virology and epidemiology can give people an estimate of how risky something is, but can’t tell people how much risk is too much, or which mitigation measures impose too much burden.

The confusion comes from the fact that this shift to personal responsibility wasn’t made clear, any more than the shift away from it was made clearly enough back in the spring of 2020.

There was a political element to the shift both times — and that’s fine as long as it’s informed by good science and it’s what people want.

Faye Flam is a Bloomberg Opinion columnist and host of the podcast “Follow the Science.” © 2021 Bloomberg. Distributed by Tribune Content Agency.