Marc Lipsitch Profile picture
Infectious disease epidemiologist and microbiologist, aspirational barista. Director @CCDD_HSPH Tweets in personal capacity.
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Dec 21, 2021 4 tweets 2 min read
Hey #econtwitter is there a common explanation behind 1) the incomparability of medical data from different EMR instances; 2) the incomparability of mattresses made by different manufacturers and sold by different retailers 3) the incompatibility of different mfg camera lenses? Feels like the common thread may be that the opportunity to prove oneself better/ better for the cost that would arise from comparability is less appealing than the risk of being proven worse; better to hold onto market share from loyalists than risk competition.
Dec 18, 2021 21 tweets 5 min read
the following thread is purely my personal opinion as a @CCDD_HSPH @HarvardEpi epidemiologist. I would welcome feedback though I am trying to take some breaks so don't promise to reply. Thanks in advance to anyone who provides critique or further info Impact of #Omicron obviously depends on severity. Number of cases is growing exceptionally fast and several countries have seen such growth continue for quite a while (weeks, which is a lot of time with doubling times of small number of days
Dec 6, 2021 7 tweets 2 min read
Clear explainer of a very carefully nuanced report. While the main thing to say is "small numbers," it does seem that the average severity among those in the hospital is comparatively low. Two thoughts about interpretation: 1/ Omicron growing very fast. Patients hospitalized for COVID are typically (not always) well into their infection. In a fast-growing epidemic, the proportion infected 10d ago, say, is lower on any given day than in a slow-growing one. This alone could cause unusually lo ...
Aug 18, 2021 17 tweets 18 min read
@CT_Bergstrom @jsm2334 Certainly this kind of bias merits consideration. I think the particular figure cited in that table is an example of Simpson's paradox, which is a special type of confounding. @CT_Bergstrom @jsm2334 For those new to these terms, confounding is just the problem that (in this case) vaccine is not randomly distributed in the population, so the vaccinated have different risks from the unvaccinated for reasons other than their vaccine: in this case, age.
Aug 13, 2021 7 tweets 2 min read
As often happens, the headline is too simple for the more subtle message of the article… The article's main point is unarguable: "we cannot control the delta variant by maximizing the immunity of only a segment of the population."
Jul 20, 2021 14 tweets 3 min read
At the risk of boiling down too much and certainly losing some detail, one way to summarize this wonderful thread is that when we think about vaccine effectiveness, we should think of 4 key variables: 1 which vaccine, 2 age of the person, 3 how long after vax, 4 vs what outcome. We've been using the simple view that the major vaccines in use in the US/Europe are possibly less effective against infection/symptoms when a variant is involved, but remain highly effective against severe outcomes. Published data so far support this view.
Jul 7, 2021 8 tweets 2 min read
Now published led by @G_RegevY and with @rebeccajk13… . . Different approach from many other VE studies, following HCW vaccinated vs unvaccinated, tested when exposed to a case, to assess VE against infection given exposure, consistent with our recommendations in…
Jun 13, 2021 11 tweets 5 min read
Now out with @rebeccajk13 Interpreting vaccine efficacy trial results for infection and transmission…
funded in part by #SeroNet In which we show that earlier work by Rinta-Kokko et al on interpreting prevalence measures for vaccine efficacy generalizes to the COVID-19 case and that the odds ratio for PCR+ in vax vs unvax persons swabbed at random
May 25, 2021 4 tweets 2 min read…. A key point: lab leak does not imply manipulation and manipulation does not imply ill intent. I disagree with @SenTomCotton on many many things but this set of tweets quoted in the article lays it out correctly
May 13, 2021 28 tweets 6 min read
This tweet got me thinking again about a topic that's been on my mind for the last several weeks and throughout the pandemic. In principle I fully agree with @flodebarre that people should evaluate arguments for logical soundness and consistency with facts, not who makes them. But many people have asked me (most recently @AmyDMarcus) how thoughtful people should know whom to trust in getting information (science) and advice (for personal actions) and opinions (about policy) on a topic like COVID
May 13, 2021 5 tweets 4 min read
In this clip @SenRandPaul FALSELY claims… that the @cambridgeWG has characterized work at the Wuhan Institute of Virology as gain-of-function. I and many other @cambridgeWG support proper investigation of SARS-CoV-2 origins including the lab leak hypothesis and continue to oppose many forms of GOF research but it is just fabrication to say we have made any statement as a group about work in Wuhan.
May 12, 2021 4 tweets 1 min read
Really important @nytimes article on how easy access to vaccines remains a key issue not just hesitancy…. I’d add two points less explicit in article 1. People say that seeing others get vax without incident reduces their hesitancy. If so then each vaccine administered to those where access is the main problem can have a multiplier effect in overcoming hesitancy in others.
Apr 30, 2021 4 tweets 3 min read
Great that attention is remaining focused on #AMR a big problem.… . But the relentless claims that this is primarily or largely a problem of agriculture are not evidence-based. Some years ago @BillHanage and I and @G_RegevY and our students pointed out the absence of strong evidence (while acknowledging challenges of generating it)…
Apr 19, 2021 4 tweets 1 min read
Is there some bizarre legal notion of causality at play here that the force used would have had to be such that it would have killed anyone, not just the actual person it did kill? I'm willing to believe that the law traditionally has such a notion (or not -- hope some lawyers will help me understand) but if so it seems truly indefensible. We all have the preexisting condition of being mortal. We each have a different breakpoint for how much...
Mar 22, 2021 11 tweets 4 min read
.@alisonannyoung has been one among the most active, persistent, and fair-minded reporters covering lab accidents in the US @USATODAY. This long piece makes the serious case for investigating poss lab origin for #SARSCoV2.…. This is not about conspiracy theories or China-bashing. This is about the basic principle, at least as old as Rev. Bayes and Sherlock Holmes, that when something unusual happens, you have to consider explanations that are also individually unlikely.
Mar 15, 2021 4 tweets 3 min read
CONGRATULATIONS DR. @AccorsiEmma defending her PhD with flying colors today. Thanks especially to @chuttenh who supervised much of the work linking microbiome and #epidemiology #EpiTwitter and to committee members @SHaneuse and @BillHanage @HarvardEpi @CCDD_HSPH @HarvardChanSPH Two of her thesis papers have been published.…
Feb 28, 2021 18 tweets 5 min read
New preprint on estimating and Interpreting vaccine efficacy trial results for infection and transmission | medRxiv. With ⁦@rebeccajk13⁩. Long discussion on applications to observational VE studies… tl;dr: Analyze separately cases ascertained for different reasons. Don't combine those found because symptomatic with those found by screening a cross section or by testing contacts.
Feb 25, 2021 17 tweets 7 min read
Our paper on identifying and mitigating biases in epidemiologic studies of #COVID-19 is now out and is #OA .…. Skillfully led by
this project involved much of our group and many discussions arising from papers we were reading. including @XuetingQ @EvaRumpler @LeeKShaffer @rebeccajk13 Ed Goldstein @NeneRiehus from @CCDD_HSPH with special guests @mats_julius and @mugecevik .
Feb 25, 2021 6 tweets 3 min read
@ZoeMcLaren Thanks for tweeting about this article. I'm going to leave the matching issue for another day, but I want to add a note of caution as one of the authors. We did not claim, and the data do not directly address, the reduction in total infections. @ZoeMcLaren We used the word "documented infection" to highlight the fact that many infections may have gone undocumented, especially those not symptomatic. The documented infections is a mixture of symptomatic (probably most of them) and asymptomatic (probably a smaller fraction)
Jan 31, 2021 4 tweets 3 min read
@profshanecrotty Thanks @profshanecrotty for another super informative thread (ht @HelenBranswell for tweeting). My 2 cents is just to remember that the comparison between sero+ and sero- in the control arm in Novavax was not randomized and involved ~40 cases in each group. @profshanecrotty @HelenBranswell Study was of course not designed to assess natural immunity, so kudos to the scientists for reporting these important data, but caution in interpretation. Several reasons to expect bias in observational seroprotection studies like this…
Jan 31, 2021 4 tweets 2 min read
Reupping this. Existing vaccines may well have been unable to get us to the herd immunity threshold before the variants made things harder. Now more unlikely. But if we can identify (hard) and vaccinate (harder) the most vulnerable it will make continued spread less destructive.…