The effects reveal a dark fact about herd immunity.
After a dramatic winter and long summer, it turns out that Covid-19 has penetrated every nook and cranny of the United States. But scientists are so sure, based on in-depth new research.
In the United States, most Americans have not yet been exposed to the virus, according to a poll published Friday in The Lancet.
Based on a survey of 28,503 people who were receiving dialysis treatment, the study reports that 8 percent of people tested positive for coronavirus antibodies. Based on that sample, the authors estimate that 9.3 percent of the US population at large has coronavirus antibodies.
The study was funded through Ascend Clinical Laboratories, a laboratory that receives samples from dialysis laboratories. The studies were carried out by a team from Stanford University.
Dialysis patients may not be the best representation of the American population: They are older and less likely to faint in public. But Wafaa El-Sadr, director of the Global Health Initiative at Columbia’s Mailman School of Public Health, says the estimates do provide useful information, however. El-Sadr was not involved in the investigation.
“[Seroprevalence, or the extent of a pathogen in a population], the knowledge gathered so far in the US has had its limitations,” El-Sadr tells Inverse. “They tried very hard. . . to make it as representative as possible. “
Thomas McDade is the director of Northwestern’s Human Biology Research Laboratory and is also not involved in the study.
“We want to be careful before jumping to conclusions beyond the dialysis patient population,” he told Inverse.
However, we can still glean insights from this data, McDade observes. For example, things that can simply expect exposure to the virus, such as where a user lives or demographic trends, reveal where the virus has spread and to whom.
The seroprevalence of antibodies against the coronavirus in the state, based on samples taken from dialysis patients.
States with Covid-19 antibody percentages: The team collected dialysis knowledge from 1,300 clinics across the country. These patients were tested for antibodies in July.
Since it can take two to three weeks for a sufficient amount of antibodies to be detected in a test, the survey gives an idea of how many other people have had antibodies in June.
That means this is a snapshot of the time before the virus re-emerged this summer, but after it devastated the Northeast and hot spots like Louisiana in March and April. This trend is reflected in the antibody data, which differs greatly by region:
“At that time, the Northeast has been hit the hardest with by Covid-19,” El-Sadr says. “It’s not surprising that there would be a higher seroprevalence noted in those individuals, compared to [people in] other regions in the country.”
McDade notes that regional differences were expected, due to the disparate way US states created Covid-19 policies and population density in each region.
“The truth is that there are many regional diversifications in seroprevalence, depending on population density and timing of policies,” he says.
Black or Hispanic people were 3. 9 times more likely to have antibodies to the coronavirus than white people, according to the study.
An accompanying observation written by scientists at Imperial College London notes that racial disparities in Covid-19 exposure are in line with trends reported in England, representing an “alarming gap” that “demands urgent attention”.
The costs are high: The Covid Tracking Project reports that Black people in the United States are dying from Covid-19 at a rate 2. 4 times higher than other white people.
Population density was correlated with antibody levels, but El-Sadr suggests that family density could be a better measure.
The study also showed that people living in places with a population density greater than 8,607 people per square kilometer were more likely to have antibodies. The link “makes intuitive sense,” El-Sadr says, but there are other explanations from past antibody studies that raise nuances.
The divide between rich and poor — In New York City, for instance, Manhattan has the most people per square mile of all the boroughs. However, it has the lowest percentage of people with antibodies. That’s because while there are more people per square mile in Manhattan, there are fewer people sharing a single household (Covid-19 spreads easily within a household), says El-Sadr.
“You’ll notice that boroughs like Queens and Brooklyn, which have higher family density, are the ones that have been hit the hardest,” he says.
This means that, when focusing on the density of a city, it would be better to take a closer look at the number of people sharing a single household, which in any populated city is a key indicator of the source of income or wealth.
Thinking beyond herd immunity – Serology surveys are typically used as markers of exposure, not immunity. Scientists are still unsure how immunity to Covid-19 works or how long it lasts. This 9.3 percent number still suggests is that herd immunity through natural infection is out of reach anyway, placing additional import on developing a vaccine and rolling it out nationwide.
“It’s extremely unlikely, if not impossible, that we’re going to reach herd immunity through natural infection,” El-Sadr says.
Although we were close and long-term immunity was guaranteed (we don’t know yet), the burden of allowing the virus to spread rampantly was high. High seroprevalence very similar to a single measure: coronavirus deaths equivalent to 100,000 people.
As El-Sadr explains, this places an additional responsibility on the country not only to develop an effective vaccine, but also to roll it out across the country, especially in groups that are at higher risk of death.
“I think the message to me is that in the case of vaccines, we’re going to have to have plans in place,” he says.
“We have a very broad national strategy on how we’re going to get this out to all the other people who want it because, looking at a map, it looks like we have to cover the whole country. “
This article was originally published on September 25, 2020.