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Making sense of the recent Covid-19 spike

The pandemic isn’t over in the US — but it is changing.

Commuters wearing protective face masks ride a bus in Brooklyn on July 13, 2021.
Spencer Platt/Getty Images

Covid-19 cases are on the rise in the United States again. But this time, the story is more complicated than it was in previous waves.

Since early January, when the United States hit a peak of 260,000 new cases every day on average, case numbers have been in more or less constant decline. Tens of millions of people were inoculated against Covid-19 in the following months. By late June, the country was averaging just 11,000 new cases per day.

But as of July 18, the US is seeing more than 31,000 new cases daily on average, nearly triple the case levels of just a few weeks ago.

Our World in Data

So far, hospitalizations have not increased as much: They’re up about one-third compared to two weeks ago. Deaths, likewise, are still comparatively low: a seven-day average of 258, compared to January when the US was losing more than 3,000 people per day. Both measures are still growing, if not yet as rapidly as cases.

Confirmed cases are a leading indicator. Somebody tests positive for the disease, but it may take two weeks for them to become sick enough to go to the hospital and even longer for them to die if they do not recover. (One caveat: Testing rates have dropped significantly in the past few months, so we may not be detecting every new case. But that only makes the rise in confirmed cases more concerning.)

This is still true — when cases accelerate, so do deaths, eventually — and the current trends reflect that basic reality.

But this time, about half of the country is now fully vaccinated against Covid-19. Some of those people could still contract the virus, but their illness is much more likely to be mild if they have received the vaccine. The Biden administration announced in early July that nearly all the Covid-19 hospitalizations and deaths being reported are of unvaccinated people.

“The decoupling between cases and deaths has really occurred,” Andrew Pavia, who specializes in infectious diseases at the University of Utah, told reporters at an Infectious Diseases Society of America briefing last week. “We’re seeing an increase in deaths but not nearly to the degree previously.”

Still, so long as the virus is circulating, there are risks, especially to the half of the population who haven’t been vaccinated. The delta variant appears more transmissible than those that came before it, and, while the vaccines seem to be holding up well against it, it is still accounting for a bigger and bigger share of cases in the US.

Hospitalizations and deaths are also becoming more prevalent among younger people, another distinction from prior surges.

All in all, the situation is much messier than it was last year, when hospitalizations and deaths would grow like clockwork following a rise in cases. Here are three factors to keep in mind going forward.

1) Unvaccinated people are still very vulnerable to Covid-19

If you have not been vaccinated, you do not have protection against the coronavirus — and the increasingly prevalent delta variant appears more dangerous than previous iterations of the virus. Right now, it accounts for most new cases in the US.

As Vox’s Umair Irfan explained, the delta variant appears to be 60 percent more transmissible than the alpha variant first identified in the United Kingdom — which was likely already 60 percent more transmissible than the version of the virus first identified in humans.

Early evidence is mixed, but some suggests the delta variant may also be more virulent: A study conducted in Scotland found that people who had contracted the delta variant were twice as likely to end up in the hospital, though the death rate did not appear to be significantly worse.

“As greater numbers of non-vaccinated persons acquire the delta variant, hospitalizations may indeed rise,” David Celentano, an epidemiologist at the John Hopkins School of Public Health, told me.

Different states also have different degrees of vulnerability, with vaccination rates by state ranging from 78 percent of Vermonters being fully vaccinated to just 42 percent of Alabamians. That has translated to the growth in cases: The states seeing the most new cases (including parts of the South, Midwest, and the West) per capita all rank in the bottom half of states in vaccination rates.

A health care worker passes out water to people waiting in the observation area after receiving a dose of a Covid-19 vaccine on March 30, 2021, in Apple Valley, California.
Mario Tama/Getty Images

Then there is the changing nature of which age groups are being affected by Covid-19: According to the Kaiser Family Foundation’s polling, 85 percent of all people 65 and over say they have been vaccinated. But that percentage drops among younger cohorts, to 66 percent of people 50 to 64, 59 percent of people 30 to 49, and 55 percent of people 18 to 29.

2) Vaccines are protecting the people most vulnerable to Covid-19

These trends contain both good and bad news. The bad news is self-evident: Because younger people and people in certain states are less likely to have been vaccinated against Covid-19, they remain more likely to contract the disease. Especially as the delta variant becomes more dominant, a higher share of them will end up in the hospital. Some will die.

According to CDC data, the share of people hospitalized with Covid-19 who are ages 18 to 49 has grown from 20 percent of the total in January to more than 40 percent in mid-July. Americans 65 and over made up more than half of Covid-19 hospitalizations in January; they now account for less than 30 percent.

To be clear: Overall hospitalizations are still way down from their peak, so the raw number of young people getting seriously ill is not as large as the number of hospitalizations among older people during the worst of the winter surge. But, relatively speaking, younger people are now making up a bigger share of hospitalizations.

The good news is the other side of this trend: The people who are the most vulnerable to dying of Covid-19 have much more robust protection than they did last year. We have known from the start of the pandemic that age, as much as anything, is the best proxy for a person’s risk of succumbing to Covid-19.

That’s why nursing home residents and workers were prioritized when mass vaccinations began in early 2021. According to an AARP analysis of federal data, nearly 80 percent of people residing in nursing homes were fully vaccinated against Covid-19 as of late June.

Over the course of the pandemic, they have accounted for a disproportionate share of Covid-19 deaths — 133,482 out of 608,000 total US deaths. But death rates among that population slowed significantly once vaccinations took off. In early January, US nursing homes reported more than 5,000 resident deaths every week, according to federal data.

In the last week of June, nursing homes reported just 147 resident deaths. That represents remarkable progress in protecting the most vulnerable.

3) Vaccinated people can contract Covid-19, but cases are almost always mild

The Covid-19 vaccines are very good, but they aren’t perfect. Some number of people who have been fully vaccinated will contract the coronavirus, and they may also account for some of the rising case numbers.

When the Pfizer/BioNTech and Moderna vaccines were first approved, it was the astounding 95-percent efficacy rates that got all the attention. But even then, that meant a very small number of vaccinated people did get sick.

That share will grow as the delta variant becomes more dominant; as Irfan reported, the initial evidence suggests the Pfizer/BioNTech vaccine is still 80 percent effective in preventing illness. But that means a larger number of vaccinated people may contract the virus and feel symptoms as the variant continues to spread.

That is still a high success rate. The World Health Organization said last week that most vaccinated people who do contract the delta variant experience no symptoms. They may also be less likely to spread the virus, as they appear to shed less of it, CDC Deputy Director Jay Butler told reporters at the Infectious Diseases Society of America briefing.

And the vaccines are still providing impressive protection against severe illness, which is reflected in the minuscule number of vaccinated people being hospitalized or dying of Covid-19.

“Breakthrough infections tend to be milder,” Butler said. “Even if infection occurs, [vaccination] decreases the risk of hospitalizations and death.”

Rising cases are not ideal. Millions of Americans are still vulnerable to Covid-19, and a more dangerous variant of the virus is taking hold. The number of deaths occurring each day is still the equivalent of a jetliner crashing every 24 hours.

But this is a different kind of wave than the ones that preceded it, with nearly 160 million Americans and counting now fully vaccinated. The solution is the same as it’s been for the past six months, as Celentano told me over email: “The best way to avoid the acquisition of SARS-CoV-2 is to get vaccinated now!”

Otherwise, as long as the virus is circulating, there are risks.

“The more virus that circulates, the more mutations that occur, and greater chance of the emergence of yet another new variant,” Jen Kates, director of global health at the Kaiser Family Foundation, told me.

A new variant that is more deadly, more transmissible, or more resistant to vaccines “would of course have more severe public health implications.”