Why Hospitalizations Are Now a Better Indicator of Covid’s Impact

The world has a new Covid variant, Omicron, that’s expected to drive up cases if it becomes the dominant strain in the coming months. Much remains unknown, including how quickly Omicron will spread in more highly vaccinated areas, or whether it causes more mild disease than Delta, the variant the United States is continuing to battle.

Thankfully the variant is arriving in a different pandemic landscape in the United States: one in which vaccines, tests and, soon, oral treatments are available. The country will need a new framework for thinking about what comes next, and in highly vaccinated areas, focusing on a different set of numbers, hospitalizations, rather than case counts, can better tell us how we’re doing.

America is in the slow process of accepting that Covid-19 will become endemic — meaning it will always be present in the population at varying levels. But the United States has effective tools to deal with that reality, when it happens in the future.

Learning to live with the virus long-term will require changes in both mind-set and policy. Relying on Covid-19 hospitalizations as the most important metric to track closely will provide the most reliable picture of how an area is faring with the virus. And by focusing attention on the number of hospitalizations, health professionals can better focus on reducing them.

This becomes especially important as case counts become more complicated. A positive case of Covid-19 doesn’t mean what it used to if you are vaccinated. Most breakthrough infections, which will grow as the number of vaccinated people increases, so far remain mild. Although antibodies wane over time and may be affected by variants, T cells and B cells generated from vaccines should continue to offer protection against severe illness. Right now, in areas of high vaccination, an increase in cases does not necessarily signal a comparable increase in hospitalizations or deaths.

Many countries put more weight on hospitalizations than case counts when it comes to making decisions about restrictions like lockdowns. Singapore, one of the most vaccinated countries in the world, started focusing its daily Covid reports on hospitalizations rather than cases in September. Its health ministry reports that, over the last 28 days, of the 41,632 people infected, 98.7 percent had mild or no symptoms. The country has had very strict Covid policies and is only beginning to loosen them.

Many areas in the United States still have a way to go on vaccinations. So far all variants can cause serious disease in unvaccinated people, and there are areas of the United States that are experiencing surges in hospitalizations. But in counties and states with high vaccination rates, policymakers should stop considering bumps in case numbers alone as the criteria for restrictions, although they should continue to monitor data on reported infections tallied by health departments.

The Centers for Disease Control and Prevention relies on case counts per 100,000 individuals, not hospitalization data, for its recommendations on mask wearing, including for children, regardless of vaccination levels. Some college campuses and school districts are still moving classes online when vaccinated healthy students test positive, or closing their dining halls and canceling events.

Some places are making the shift to hospitalization-based guidance. Marin County, Calif., dropped mask mandates in early November when the county’s Covid-19 hospitalizations were at a sustained low. The county’s cases have gone up and down in the past two weeks, though Omicron could change that. But Dr. Matt Willis, the county’s health officer, said that the decision to bring back masks will no longer rely on case counts. Instead, after Omicron was identified in the Bay Area, he reiterated that the county (which has vaccinated 89 percent of eligible people) plans to use hospitalization numbers to consider whether to impose future restrictions such as mask mandates.

A new mask mandate would be considered if the county’s Covid-19 hospitalization rate reaches five per 100,000 residents, which is about 13 people in the hospital. “Despite the fact that we’re seeing surges in cases, we are stable with regard to hospitalizations,” Dr. Willis said, as The San Francisco Chronicle reported. “The relationship between cases and severe illness has been uncoupled because of high vaccination rates.”

A final reason to rely more heavily on hospitalizations and less on case numbers to lead policy in highly vaccinated areas is that the latter metric is becoming less accurate. With at-home tests becoming more widespread, more people are testing outside of the public health infrastructure or, because of the social consequences of even a mild infection, not testing at all.

To be sure, case counts are still important to track in all areas. Tracking cases provides important data on who is getting breakthrough infections, which will be important for targeting boosters in the future if those infections become more severe. In addition, identifying hot spots as they develop helps local health officials work with the C.D.C. to make sure antiviral treatments are plentiful where needed. One of the major elements of flu tracking is monitoring for worrisome mutations, because of the potential for flu to switch from endemic to pandemic. With Covid-19, as we transition from pandemic to endemic, variants should continue to be tracked.

If the United States focused more on hospitalizations versus cases, health authorities could expend more resources on reaching people who are unvaccinated and at high risk for hospitalization. This may include people who are unlikely to be covered by vaccine mandates: older people and those with medical conditions employed in small companies that are exempt from mandates, people who are self-employed or on disability (often at risk for severe Covid-19) and retirees. This is millions of Americans.

Some policymakers may be wary of not using case numbers as the primary metric to guide public behavior and policy. As cases become more complex, however, health departments should still monitor infection numbers, but guidance should be tied to hospitalization metrics. When rising cases do not reliably predict hospitalization surges, hitching Covid policies to cases alone is no longer effective policy — or good public health.

Dr. Monica Gandhi is a professor of medicine at the University of California, San Francisco, and the director of the U.C.S.F. Center for AIDS Research.Dr. Leslie Bienen is on the faculty at the O.H.S.U.-Portland State University School of Public Health. She has researched zoonotic (from nonhuman animals to humans) disease transmission.

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