New York City has published the results of more than 1.8 million coronavirus antibody tests, along with a trove of demographic data that confirms prior testing and hospital data showing that poorer neighborhoods in the Bronx and Queens have been hardest hit by the pandemic.
The data, which was initially released on the city’s coronavirus data website on Tuesday and will be continually updated, breaks down positive antibody rates by borough, zip code, age and sex between April 11th through the week of August 8th. The city has categorized the tests based on the date of specimen collection, and aggregated them by week. A person tested twice in one week would only be counted once in that week. It may not, however, account for individuals who took the test again on a different week.
New York City was the first municipality in the country to release such detailed data, according to Dr. Dave Chokshi, the city’s newly appointed health commissioner.
“The concept of disseminating data and metrics is so important,” said Denis Nash, an epidemiology professor at the CUNY School of Public Health, who praised the city for creating what has become a robust coronavirus data website.
“Could they do more?” he said. “Of course. But when they have something new and important, they put it there.”
Overall, 26% of those tested in the five boroughs had antibodies to the virus. The number is larger than the smaller study released by Governor Andrew Cuomo which showed that nearly 22% of of some 28,000 city residents surveyed had antibodies.
At one point, the positivity rate of antibody testing soared to as high as 61% in early April. It has since leveled off to around 20% over the last three weeks.
Among the boroughs, the Bronx had the highest rate, that of 33%, while Manhattan had the lowest rate, that of 19%.
Income played a dominant role. Of those tested in neighborhoods with the highest poverty level, 35% tested positive. By comparison, that figure was almost 19% among who were tested in neighborhoods with low poverty.
Along gender lines, women got tested at a higher rate, but more men tested positive, 28% compared to 25%.
At the neighborhood level, Corona, Queens, where nearby hospitals were inundated with coronavirus patients early during the crisis, had the highest positive testing rate for antibodies at 52%. Similarly Brooklyn’s Borough Park, where the Hasidic community was badly hurt by the virus, saw a positive testing rate of nearly 47%.
The high rates of antibodies has spurred more discussion of the possibility of herd immunity in certain neighborhoods in New York City where the virus took a toll. In Borough Park, where life has nearly resumed back to normal, some members of the ultra-Orthodox Jewish community have asserted that they may have reached herd immunity. But on Wednesday, the city announced that there was an “uptick” in coronavirus infections in the neighborhood that health officials said they traced back to a wedding that violated social distancing guidelines.
Some have also speculated whether herd immunity might explain the city’s low infection rates, which have been below 2% for more than two months. To date, more than 227,000 New York City residents have been infected with coronavirus. More than 23,600 New Yorkers have died either directly or indirectly from the disease.
Wafaa El-Sadr, an epidemiology professor at Columbia University, told the New York Times, “If antibody tests are accurately identifying those who have been infected and if these antibodies are protective, are some communities in N.Y.C. close to achieving herd immunity, like Corona in Queens, for example.”
But during a press conference on Wednesday, Mayor Bill de Blasio shot down the idea, saying, “I don’t think we have any evidence of herd immunity anywhere in New York City.”
“We’re nowhere near that point from what we know,” he added.
The concept of herd immunity is highly speculative given the little scientists know about coronavirus and the protection its antibodies confer.
In a confusing update last Friday, the Center for Disease Control and Prevention noted that people who have tested positive for COVID-19 do not need to quarantine or get tested again for up to three months as long as they do not develop symptoms.
Many interpreted the new guidance as meaning that infected individuals have immunity for up to three months, something that a small study in China suggested. Later in the day, the CDC issued a statement pushing back on reports that the agency was suggesting infected individuals have any immunity.
The World Health Organization has maintained that there is still no evidence that people who have recovered from COVID-19 and have antibodies cannot get infected a second time. Some have also questioned the reliability of antibody tests.
“The problem is, we don’t know how much protection people have after that and whether that means they’re fully protected or not,” Dr. Jay Varma, the city’s top health adviser, told reporters on Wednesday. “What we’re seeing in the situation in the neighborhoods where we see higher infection rates is that, you know, everybody should still consider themselves potentially at risk of infection. It’s just safest to plan that way.”
Nash said that regardless of the level of immunity, the percentage of New Yorkers with antibodies still is “well below what we need.”
“While it may be something that can help slow transmission, I don’t think it’s something where we can let our guard down,” he added.
The data has other limitations, namely that the sample was not a random selection of New Yorkers. Nash speculated that those who submit to antibody testing are more likely to be those who believe they may have been infected and thereby are also more likely to be positive.
Income and access to testing are also likely factors. Certain affluent and largely white parts of Manhattan around and below Central Park saw high testing rates even though these neighborhoods had among the lowest rate of positive tests.
“There’s a lot of guesswork that has to happen around interpretation when you don’t know the underlying reason why people got the test,” he explained.
While experts will likely be interested in dissecting the city’s antibody data, Nash said that diagnostic test data, which the city also reports and which indicates the current positive testing rate, is generally more useful in guiding the behavior of the public.
Nevertheless, he said that seeing neighborhood data on antibody testing might offer some people validation for what they recalled and felt was happening during the peak of the crisis.
It might also, he added, “prompt you to get an antibody test.”