Huge ANTIBODY study in NYC among 40,000 health care professionals. Key #COVID19 findings:

13.7% were seropositive.

Of 6078 w/ previous PCR testing, 34.8% were PCR positive.

Of previous PCR-positives, 6.5% had with negative antibody test results. https://jamanetwork.com/journals/jama/fullarticle/2769322

2) Of the 3892 with previous PCR-negative HCP, 3490 (89.7%) were also seronegative - leaving ~10% positive.

Of 34,251 with no PCR testing, 3077 (9.0%) were seropositive.

3) “Missing data ranged from 0% to 15.4%. Working in COVID-19 units or in intensive care units were each associated with seroprevalence in bivariate analyses but not in multivariable analyses.

(TRANSLATION: crude correlation existed, but disappeared for ICU after adjustment)

4) “In a fully adjusted model, a previous positive PCR test result (relative risk, 1.52 [95% CI, 1.44-1.60]; P < .001) and reported high suspicion of virus exposure (relative risk, 1.23 [95% CI, 1.18-1.28]; P < .001) were associated with seroprevalence. “

5) “From April 20, 2020, to June 23, 2020, all Northwell HCP were offered free, voluntary antibody testing, regardless of symptoms, at 52 sites in the greater NYC area. HCP missing all data were excluded. Testing was for qualitative IgG or total immunoreactivity to #SARSCoV2”

6) FYI: seroprevalence means antibody prevalence, or what % or pop has antibodies to #SARSCoV2.

That said, note that antibodies can disappear over 1-3 months after infection, but given timeline of epidemic & testing in NYC, probably limited time for too many. But some perhaps.

7) Also note: antibody disappearing over months does NOT mean any prior immunity from infection is lost. Discussed earlier here. https://mobile.twitter.com/drericding/status/1286176254409035777 https://twitter.com/drericding/status/1286176254409035777