NYC still far from herd immunity, Mount Sinai data shows

A new study from researchers at the Icahn School of Medicine at Mount Sinai suggests that the presence of COVID-19 antibodies in the city is around 22%, still a ways off from the level that would indicate herd immunity. One widely communicated threshold for such immunity is 67% of the population.

The data further indicated that more than 1.7 million New Yorkers have been infected with the virus that causes COVID-19, the virus was in the city earlier than March 1, and the infection fatality rate is close to 1%, which is 10 times deadlier than the flu, Mount Sinai said.

"We can't bank on herd immunity," said Florian Krammer, professor in vaccinology at the Icahn School of Medicine and corresponding author on the study.

However, once a vaccine is approved and people start receiving it, the percentage of individuals with antibodies could start to reach the level associated with herd immunity or even surpass it, Krammer said. Ideally, that would be above 75% of the population, with an initial focus on vaccinating individuals at high risk of severe outcomes from COVID.

The study was published last week in the journal Nature.

The findings are based on 10,691 plasma samples from patients of Mount Sinai Health System obtained and tested between the weeks ending Feb. 9 and July 5.

Plasma samples examined for the study were from patients seen in emergency departments and from those admitted to the hospital for urgent care, Mount Sinai said. They were also from patients seen for OB/GYN visits, labor and deliveries, oncology-related visits, hospitalizations due to elective and transplant surgeries, preoperative medical assessments, cardiology office visits and other regular appointments.

Krammer also called attention to the infection fatality rate identified in the study. One takeaway for other geographic areas is that if they also have the kind of surge the city had in the early days of the pandemic, their health systems could become overwhelmed, resulting in the virus becoming more deadly, he said.

Efforts to prevent that from happening will be especially important through the fall and winter, he said, due to a coincidence with flu season.

The antibody test used in the research was developed and launched at Mount Sinai. It is able to detect the presence or absence of antibodies to the virus that causes COVID as well as the level of antibodies an individual has, the health system noted.

The study suggests that antibody levels are stable over time, Krammer said, which is a positive finding. However, he said, "we can't say for sure yet if everybody who has antibodies is protected."

The study was supported in part by the National Institute of Allergy and Infectious Disease, as well as the Midtown-based JPB Foundation, the San Francisco–based Open Philanthropy Project and other donations, Mount Sinai said. A Mount Sinai spokeswoman could not readily provide the cost of the effort.