Roughly 25{3c4481f38fc19dde56b7b1f4329b509c88239ba5565146922180ec5012de023f} of New York City has probably been infected with coronavirus, Dr. Scott Gottlieb says

About 25{3c4481f38fc19dde56b7b1f4329b509c88239ba5565146922180ec5012de023f} of New York City-area residents have probably been infected with the coronavirus by now, former Food and Drug Administration Commissioner Dr. Scott Gottlieb told CNBC on Tuesday.

Researchers at The Mount Sinai Health System in New York City published a study Monday, which suggested that 19.3{3c4481f38fc19dde56b7b1f4329b509c88239ba5565146922180ec5012de023f} of people in the city have already been exposed to the virus through April 19. 

Even if that many people have Covid-19 antibodies in New York City, the initial epicenter of the U.S. outbreak, the researchers noted that would still be well below the estimated 67{3c4481f38fc19dde56b7b1f4329b509c88239ba5565146922180ec5012de023f} needed to achieve herd immunity, which is needed to eradicate the virus. The study has not yet been peer-reviewed nor accepted by an official medical journal for publication.

Based on their findings, the researchers concluded that about 0.7{3c4481f38fc19dde56b7b1f4329b509c88239ba5565146922180ec5012de023f} of everyone infected with the virus in New York City died due to Covid-19. However, Gottlieb said the infection-fatality rate, which factors in asymptomatic patients who never develop symptoms, has likely risen since mid-April.

“If you probably took that out to now, you did a seroprevalence study now, you’d probably see that the infection-fatality rate’s a little higher because more people succumbed to the infection over the course of time from April to now,” he said on CNBC’s “Squawk Box.” “And you’d probably see that the seroprevalence is a little higher because more people have gotten infected, so my guess is probably around 25{3c4481f38fc19dde56b7b1f4329b509c88239ba5565146922180ec5012de023f} of New York has now been infected with Covid.”

The infection-fatality rate is likely lower than the case-fatality rate, which looks at the percent of people who have symptoms and end up dying. Gottlieb said the case-fatality rate might be closer to 1.1{3c4481f38fc19dde56b7b1f4329b509c88239ba5565146922180ec5012de023f} or 1.2{3c4481f38fc19dde56b7b1f4329b509c88239ba5565146922180ec5012de023f}. 

The findings of the study are in line with what other researchers, including those for New York state who conducted their own seroprevalence study, have found, Gottlieb said, which helps bolster confidence in such studies. 

“We can start to believe that this probably represents an approximation of what the real result is,” he said.

The relationship between the presence of antibodies and immunity when it comes to the coronavirus remains unclear. The authors of the study noted that previous research into other coronaviruses has indicated that antibodies confer immunity. However, health officials, including Gottlieb and White House health adviser Dr. Anthony Fauci, have warned that the level and duration of immunity provided by antibodies is still unclear. 

The researchers said the antibody test used in the study has a sensitivity rate of 95{3c4481f38fc19dde56b7b1f4329b509c88239ba5565146922180ec5012de023f}, meaning it picks up positive cases 95{3c4481f38fc19dde56b7b1f4329b509c88239ba5565146922180ec5012de023f} of the time, and a specificity of 100{3c4481f38fc19dde56b7b1f4329b509c88239ba5565146922180ec5012de023f}, meaning it accurately reflects negative cases 100{3c4481f38fc19dde56b7b1f4329b509c88239ba5565146922180ec5012de023f} of the time. That means the tests could produce a false negative result, but not a false positive antibody test. All tests were analyzed in a research laboratory setting. The sample of patients used to determine the prevalence of the virus in the general population was composed of patients who presented at Mt. Sinai for a regular medical procedure or check up, unrelated to Covid-19. 

The authors of the Mount Sinai study acknowledged some factors that might have biased their sampling of the general population, but said “it nevertheless provides a window into the extent of seroprevalence in NYC.” The study was partially funded by the National Institute of Allergy and Infectious Diseases, the Collaborative Influenza Vaccine Innovation Centers, the JPB foundation and other donors.

Since April, New York and the tri-state region has managed to significantly drive down its level of spread, which means the “seroprevalence would likely not change significantly unless new infections rise again or vaccines would become available,” the researchers said.