NEW: Early results from coronavirus antibody tests in general population

  • Prevalence of Covid-19 ranged from 2.49% to 4.16%
  • In Santa Clara County, that means an estimated 48,000 to 81,000 people were infected
  • That is 50-85-fold more than the number of confirmed cases

The first early results are on from coronavirus antibody testing in a general population: Covid-19 (SARS-CoV-2) is much more widespread than positive tests indicate.

Watch my interview with scientist Dr. Jay Buttacharya

The goal of the study is to find out how prevalent Covid-19 has been beyond those who have tested positive. Many Americans have had the disease in the recent past but had few or no symptoms. They are believed to be largely immune from a repeat infection, or from infecting anybody else.

Knowing how many truly had coronavirus will allow scientists to calculate the first accurate death rate. Until now, the publicized mortality rates have been skewed higher than they really are because officials have only counted deaths among those who tested positive. A more accurate number will come from calculating deaths among everybody who had coronavirus, including those who were never diagnosed with it.

According to a preprint scientific paper on a part of the study conducted in Santa Clara, California, the population prevalence of COVID-19 in Santa Clara ranged from 2.49% to 4.16%.

That works out to a range of an estimated 48,000 to 81,000 people infected in Santa Clara County by early April. Those numbers are 50-85-fold more than the number of confirmed cases.

The scientists of the study say the population prevalence of Covid-19 (SARS-CoV-2) antibodies in Santa Clara County implies that the infection is “much more widespread than indicated by the number of confirmed cases.”

Coronavirus in Santa Clara County, California is “much more widespread than indicated by the number of confirmed cases.”

Study scientists

That make the true death rate, at least in Santa Clara, significantly lower than earlier publicized figures.

The scientists are continuing their research in other locations.

WATCH: My story with one of the scientist on the study, Stanford’s Dr. Jay Bhattacharya

The study paper abstract follows, and the link to it is below that:

Background Addressing COVID-19 is a pressing health and social concern. To date, many epidemic projections and policies addressing COVID-19 have been designed without seroprevalence data to inform epidemic parameters. We measured the seroprevalence of antibodies to SARS-CoV-2 in Santa Clara County. Methods On 4/3-4/4, 2020, we tested county residents for antibodies to SARS-CoV-2 using a lateral flow immunoassay. Participants were recruited using Facebook ads targeting a representative sample of the county by demographic and geographic characteristics. We report the prevalence of antibodies to SARS-CoV-2 in a sample of 3,330 people, adjusting for zip code, sex, and race/ethnicity. We also adjust for test performance characteristics using 3 different estimates: (i) the test manufacturer’s data, (ii) a sample of 37 positive and 30 negative controls tested at Stanford, and (iii) a combination of both. Results The unadjusted prevalence of antibodies to SARS-CoV-2 in Santa Clara County was 1.5% (exact binomial 95CI 1.11-1.97%), and the population-weighted prevalence was 2.81% (95CI 2.24-3.37%). Under the three scenarios for test performance characteristics, the population prevalence of COVID-19 in Santa Clara ranged from 2.49% (95CI 1.80-3.17%) to 4.16% (2.58-5.70%). These prevalence estimates represent a range between 48,000 and 81,000 people infected in Santa Clara County by early April, 50-85-fold more than the number of confirmed cases. Conclusions The population prevalence of SARS-CoV-2 antibodies in Santa Clara County implies that the infection is much more widespread than indicated by the number of confirmed cases. Population prevalence estimates can now be used to calibrate epidemic and mortality projections.

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11 thoughts on “NEW: Early results from coronavirus antibody tests in general population”

  1. Sharyl,
    It is important to ALSO point out that if this study is true:
    (1) instead of the currently reported CASE mortality rate of 5.3%, the TRUE mortality rate is 0.06% to 0.10%, similar to flu. Since deaths are so skewed towards people over 60, under 60 with no co-morbidities could have extraordinarily low risk of mortality.
    (2) Antibody testing in the WORST areas (e.g. NYC) may show that those populations may have large portion already IMMUNE to further infection. Even if immunity doesn’t last forever, it will likely protect till vaccines are available.

  2. I have posted this & shared this onto my Facebook page but to everyone else but me it says webpage not available. Tried two different times.

        1. Sharyl Attkisson

          Some think this is good news. It means the lethality rate of coronavirus is many times smaller than originally publicized. Also these people who have already had it, according to scientists, are good to go back to work without much risk of getting sick again or passing virus to others.

  3. This virus is obviously killing a lot of people, but the question that has thus far remained unanswered is whether this is due to a high mortality rate among people who have been infected, vs. the rapidity of its spread through the general population. Until we have a reliable answer to this crucial question, we can’t know what to expect for the coming months and years. Herd immunity is not expected to be reached until 65% of the population has been infected. At this point we have no idea whether this will take one year or ten years. It may be that we are much closer to reaching this crucial turning point than previously thought. But, it is still too soon for people to be rebelling against the social distancing rules and the forced closures. Yes, it is bad for the economy and lots of people are hurting. But there remains the strong possibility that if it hadn’t been for the social distancing, the number of fatalities would have been ten times worse than it has been. This is a distinct possibility. We just don’t know. We have to err on the side of caution until we know with a high degree of certainty what the true mortality rate is and what percent of the population has already been infected.

  4. Palo Alto “April 13. The state has conducted about 215,400 tests as of April 13, with 23,338 people testing positive, according to state data.”

    I can’t believe antibody test RESULTS are still in their infancy: Brit reported about the German town weeks ago. The world’s news mgmt. might not want to tell us nature is doing its job when the big money wants to sell the world something else.

  5. My 67 year old brother has been in icu in Walnut creek John Muir hospital with cp19 and pnumonia..He called me on the phone and said they were going to treat him with Hydrochloroquine and z pack combo, which I was 100 percent behind. I am a 77 year old retired nurse, flight attendant, presently in sacramento , only 50 miles away.
    His wife took over his treatment, they intubated him and he has been in a sedated(med induced coma) since the afternoon I spoke to him.
    I am not allowed to speak to anyone but her for info and she refuses my calls, but will text me . I don’t text.
    She hates Trump and I believe she didnot let them continue with the 99 percent successful treatment.
    I was hoping to get some media attention.
    I think you used to work with my husband Bill Magee@ channel 7 in Sfo
    I felt compelled to contact you for help.
    I don’t tyoe or text but if you could find time to call me @3606789123 I would consider it an answered prayer
    Carol Magee and my email is [email protected]

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