Important results from Stanford study on prevalence of Covid-19 in the Bay Area – Peninsula Doctor update #10

The results from the study that I referenced in this morning’s letter are out, although the study findings aren’t officially peer-reviewed.

Stanford and the CDC tested 3330 volunteers in Santa Clara County on April 3rd and 4th, using a drive through finger-stick antibody test to look for evidence of prior COVID-19 infection. Participants were recruited using a Facebook ad and chosen to represent the counties geographic and demographic characteristics.

The unadjusted prevalence of antibodies in this study was 1.5%.

They then adjusted the numbers to account for the sensitivity of the test, and the demographics of those tested, compared to the true county demographics.

After adjustments, they estimate that the prevalence of antibodies to COVID-19 in Santa Clara County in early April was between 2.5% and 4.1%. This reflects between 48,000 and 81,000 people.

This number is 50-85 times the number of reported cases.

The significance of this study is profound. It tells us that there are many more asymptomatic cases than were previously thought. It also tells us that the percentage of people who are exposed that will go on to develop severe illness is much lower than previously reported. While we are not at all close to the percent prevalence that would offer people ‘herd immunity,’ it is reassuring that the percentage of people who go on to develop severe disease is low.

It will be very interesting to see how this data gets interpreted by the scientific community.

If anyone would like to have antibody tests done, please refer back to our earlier letter today. I am more than happy to place those lab orders for you. I still don’t find them available through Sutter, nor Quest, but we can do them through Stanford. I suspect that, within the next few weeks, this test will be widely available through all of the normal lab testing centers.

Please let me know if you have any questions or concerns,

Warmest regards,
Dr.Kroes & Dr.Santana
Peninsula Doctor is a concierge medical practice located in the Bay Area, city of Menlo Park, CA.