Health

How Delta is pushing the U.S. into a new phase of the Covid-19 pandemic


For the first year of the Covid-19 pandemic, hospitalizations and deaths followed infection patterns by a few weeks, as sure as night follows day.

Vaccines promised to sever those metrics. While they might not prevent all Covid-19 infections, vaccines would, experts predicted, dramatically reduce hospitalizations and deaths. And they have.

But with the highly transmissible Delta variant now circulating — mostly among the unvaccinated — the United States is seeing spikes in infections that have turned into increases in hospitalizations in some communities.

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So, how well is the country preventing hospitalizations and deaths right now?

The answer is nuanced. Vaccines are absolutely helping blunt the impact of these outbreaks — both the size and the toll in sickness and death. But vaccine uptake isn’t to the point yet where it can preclude increases in hospitalizations and deaths.

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Put another way, without vaccines, the outbreaks in Nevada, Missouri, Arkansas, and elsewhere with low immunization rates would be worse, and other states would be more vulnerable to similar spikes.

“This is a new phase of the pandemic,” Jay Butler, the deputy director for infectious diseases at the Centers for Disease Control and Prevention, said at a press briefing last week. “We’re seeing positive effects of the vaccination problem, but at the same time … it ain’t over ’til it’s over. We’re continuing to see transmission occurring, and we have a significant portion of the population that is unimmunized.”

The impact of vaccines is remarkable. They’re standing up to the variants nature has thrown our way. The overwhelming majority of hospitalizations and deaths — some 98% to 99% of the latter — are among people not fully vaccinated. (No vaccine prevents all severe outcomes.)

But so many people remain unvaccinated that, nationwide, cases have more than doubled in recent weeks — a jump driven not just by Delta, but also the country’s lapsing of mitigation efforts and people traveling and reconnecting socially. Even states like Massachusetts that have comparatively high vaccination rates have started seeing upticks in cases.

“This is becoming a pandemic of the unvaccinated,” CDC Director Rochelle Walensky said Friday. She added: “Our biggest concern is that we are going to continue to see preventable cases, hospitalizations, and sadly deaths among the unvaccinated.”

The shape and scope of the damage of a Covid-19 outbreak isn’t just determined by how many people in a given area are protected — it’s also a question of who is protected. While 56.8% of people in the United States 12 and over who are eligible for the shots are fully vaccinated, the rate is nearly 80% for people 65 and older — the population at greatest risk of getting severely ill and dying from Covid-19.

Having so many older people protected will in turn reduce the death rate among those people still contracting the coronavirus. It also explains why younger adults — who have lower vaccination rates — are accounting for a larger portion of people hospitalized now.

In Florida, for example, while people 70 and older accounted for nearly 1 in 2 hospitalized Covid-19 patients in the pre-vaccine era, they now make up just 1 in 4, according to data analyzed by epidemiologist Jason Salemi of the University of South Florida. And with the bulk of hospitalizations among younger adults, “we should absolutely not see as many deaths related to hospitalizations, because fewer of those hospitalized will die,” Salemi said.

Similar patterns are occurring in other states.

“The infection rates are highest among young people, 15 to 45,” Andrew Pavia, a pediatric infectious disease physician at the University of Utah, said about the recent increases in Utah. “The hospitalization rates are much higher in those age groups than they were earlier in the pandemic. And the rates of infection and rates of hospitalization are highest in the rural areas, and it should be no surprise to anyone that those are the same areas that have very low rates of vaccination.”

Just how many deaths will occur as a result of the recent uptick in transmission is still unclear. Even if they die at lower rates than older adults, some of the younger adults hospitalized in recent weeks will still die. But cases only started rising in the past few weeks, and it can take people with Covid-19 that long to die, and another few weeks for their deaths to be recorded.

Plus, cases are still rising.

“The deaths have remained pretty flat, but given when that increase in hospitalizations and the increase in cases occurred, I’m not surprised by that,” said infectious disease epidemiologist Brian Labus of the University of Nevada, Las Vegas’ public health school, suggesting that the state, which has had one of the country’s largest recent surges, hasn’t yet seen the full impact of that transmission.

Because so many people are protected, whatever outbreaks occur now aren’t likely to create crises for health care systems nationwide. Individual hospitals are facing a deluge of patients — hospitals in Arkansas and Missouri are under particular pressure — but even as cases and hospitalizations have built up in recent weeks, they’re still drastically down from prior months in most places. Take Utah: ICUs are at capacity, Pavia said, but hospitals haven’t had to build emergency units like they did during the winter.

Overall, it’s difficult to compare metrics like hospitalization and death rates at various points in the pandemic. Testing has fallen off in many places. Doctors have gotten better at treating Covid-19, while who is getting sick has changed. The virus has also evolved. Now dominant is Delta, but experts are still trying to sort out if it causes more severe disease on average than other forms of the virus.

Even how we think about what a “case” means has fragmented. People who still get infected by the coronavirus after being fully vaccinated face a minuscule risk of becoming severely sick, having to go to the hospital, or dying. It’s presumed that many asymptomatic or even mild cases among vaccinated people — which are evidence that the vaccines are working, because they’re not getting sick — are going undetected.

But those who remain unvaccinated (or who don’t have protection from an earlier infection) still face the same risks from a case.

The vaccines have had some help in bringing transmission down from the winter to the spring to the summer. Some chunk of unvaccinated people have been infected by the coronavirus already and are protected that way (though experts say that the protection provided by vaccines appears more robust and durable than that from an infection). Scientists are still trying to sort out seasonal influences on the virus, though typically respiratory viruses spread less efficiently in warmer temperatures. Plus, people can be outside more than in the winter — though the counterpoint to that is that it’s so hot in the summer in some places, like southern states, that people there spend more time indoors.

The way to prevent and minimize outbreaks going forward, experts stress, is getting more people vaccinated. The United States has shown it can do this: In the spring, the Alpha variant drove a spike in cases in Michigan and threatened other states. But the country vaccinated itself out of feeling more severe devastation from that variant.

Now the country has to do that again in the face of an even more transmissible variant, Delta. Because of how effectively it spreads, more people have to be protected for its circulation to slow.

At the Medical University of South Carolina, hospitalized Covid-19 patients include a mix of unprotected younger adults, but also older adults from the state’s rural areas who haven’t been vaccinated either, said infectious disease physician Krutika Kuppalli. While Charleston has a relatively high vaccination rate, many people from the rural areas — where Kuppalli sees patients through telemedicine appointments — have hardened in their resistance to the vaccines.

“Trying to get people to take a vaccine, which has been so politicized, is just really hard,” she said.


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