Trevor BedfordVerified account

@trvrb

Scientist , studying viruses, evolution and immunity. Collection of threads here:

Seattle, WA
bedford.io
Joined December 2010
691 Photos and videos Photos and videos

Tweets

You blocked @trvrb

Are you sure you want to view these Tweets? Viewing Tweets won't unblock @trvrb

  1. Jul 12

    We're recruiting a bioinformatician and a full-stack developer to the Bedford Lab to work on and . Details here: .

    8 replies 152 retweets 195 likes
    Undo
  2. Jun 30

    Follow up #2: This supports the expectation that we'll see Delta circulation influenced by degree of regional vaccine coverage.

    We know from that B.1.617.2 is primarily transmitting through the unvaccinated (or partially vaccinated) population. It's difficult to predict the size of a B.1.617.2 epidemic we'll see, but I would expect at least some correlation with regional vaccine coverage. 12/12
    Show this thread
    33 replies 57 retweets 252 likes
    Show this thread
    Show this thread
    Undo
  3. Jun 30

    Follow up #1: Prompted by question on Twitter () I just did a simple correlation of total population fully vaccinated against Delta-specific Rt across 20 states with good data. We get a decently strong negative correlation with R^2 of 0.32.

    18 replies 36 retweets 212 likes
    Show this thread
    Show this thread
    Undo
  4. Jun 30

    Although I don't have a huge amount of faith in this specific 11% estimate, at the moment, just based on what's happening in the UK, I would expect there to be a US wave driven by Delta (figure showing Rt in UK from ). 16/16

    43 replies 75 retweets 372 likes
    Show this thread
    Show this thread
    Undo
  5. Jun 30

    Another 11% of the population infected is of course substantial, though we expect lower rates of mortality on a per case basis due to vaccination coverage differing substantially across age groups (). 15/16

    4 replies 30 retweets 234 likes
    Show this thread
    Show this thread
    Undo
  6. Jun 30

    I'd hope for these two effects to largely come out in the wash. 14/16

    1 reply 15 retweets 189 likes
    Show this thread
    Show this thread
    Undo
  7. Jun 30

    Second, vaccination is not perfect and vaccine efficacy against symptomatic disease drops from ~89% against Alpha to ~79% against Delta per report (). Breakthrough infections imply a smaller fraction of the population immune than the 62%. 13/16

    12 replies 58 retweets 311 likes
    Show this thread
    Show this thread
    Undo
  8. Jun 30

    A couple obvious places where this calculation is wrong. First, vaccination and infection are not independent and instead probably anti-correlated. This would imply a larger fraction of the population immune than the 62% used above. 12/16

    4 replies 30 retweets 285 likes
    Show this thread
    Show this thread
    Undo
  9. Jun 30

    This would imply that Delta has a susceptible pool of 38% of the US population and given final size of 29% would suggest 11% of the total US population infected with Delta or 36M people. 11/16

    13 replies 89 retweets 375 likes
    Show this thread
    Show this thread
    Undo
  10. Jun 30

    CDC lists 46% of the US population as fully vaccinated. Following , we take ~30% of the US population as having been infected. Assuming that vaccination and infection are independent yields 46% + 54% x 30% = 62% of the population with immunity. 10/16

    10 replies 37 retweets 254 likes
    Show this thread
    Show this thread
    Undo
  11. Jun 30

    Inputting R0 of 1.18 in the final epidemic size equation yields 29% of the susceptible population infected in the Delta wave. 9/16

    4 replies 29 retweets 204 likes
    Show this thread
    Show this thread
    Undo
  12. Jun 30

    Variant-specific estimates of Rt from using case counts and sequence data suggests Rt of Delta variant of 1.18 averaged across 20 states analyzed. 8/16

    8 replies 33 retweets 218 likes
    Show this thread
    Show this thread
    Undo
  13. Jun 30

    We've recently seen rapid growth of Delta, where it's displacing other circulating viruses in many states. Here, predominance of Delta in Arkansas, Colorado, Missouri and Utah occurred in only ~4 weeks. 7/16

    12 replies 111 retweets 385 likes
    Show this thread
    Show this thread
    Undo
  14. Jun 30

    Notably, the (super rough) math seems to work here. Initial Rt of ~1.1 translated to ~20% of the population infected, which is close to the 18% mathematical expectation. 6/16

    2 replies 21 retweets 197 likes
    Show this thread
    Show this thread
    Undo
  15. Jun 30

    From Sep through Mar, the US reported 24M cases of COVID-19. If we assume 2.7 infections per reported case (via ) we arrive at 65M infections in a population of 328M for ~20% of the US infected in the fall/winter wave. 5/16

    4 replies 27 retweets 209 likes
    Show this thread
    Show this thread
    Undo
  16. Jun 30

    Before we get to Delta, we can see how this logic works with the fall/winter wave in the US. Here, state-level estimates of Rt were ~1.1 in Sep and Oct 2020 and declined to ~0.9 in Mar 2021 as the epidemic ran its course and left a wake of population immunity. 4/16

    1 reply 28 retweets 219 likes
    Show this thread
    Show this thread
    Undo
  17. Jun 30

    Given a specified R0, we can calculate final epidemic size in a simple SIR model with the following equation where Z is final epidemic size. For initial R0 of 1.1, an epidemic is expected to infect 18% of the susceptible population. 3/16

    4 replies 33 retweets 238 likes
    Show this thread
    Show this thread
    Undo
  18. Jun 30

    First off, epidemic size is determined by two primary factors: 1. Efficiency of onward transmission from an index case, commonly quantified as R0 2. Size of susceptible pool 2/16

    4 replies 36 retweets 270 likes
    Show this thread
    Show this thread
    Undo
  19. Jun 30

    How big of a wave of do we expect in the US from the Delta variant? Here I describe a simple approach to this question and attempt a rough back-of-the-envelop estimate. 1/16

    63 replies 673 retweets 1,931 likes
    Show this thread
    Show this thread
    Undo
  20. Jun 24

    As I've said before, I believe both zoonosis and lab leak to be plausible hypotheses for COVID origins. I'm not pushing any narrative, just trying to figure out what's going on with this particular datapoint. 15/15

    I am in the both are plausible camp. The data (as it exists) is consistent with zoonosis, but it's also consistent with lab leak. Parsing the relative probabilities of the two depends on multiple lines of evidence and is necessarily assumption ridden. 2/8
    Show this thread
    27 replies 45 retweets 349 likes
    Show this thread
    Show this thread
    Undo

@trvrb hasn't Tweeted yet.

Loading seems to be taking a while.

Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.

    You may also like

    ·