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Monica Gandhi MD, MPH Profile picture
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24 Apr, 8 tweets, 3 min read
Wanted to send you 2 articles today that indicate when an epidemic can be downgraded to endemic for an infectious disease. What is an epidemic? An epidemic is when a disease affects a large number of people within a community, population, or region. That is what was happening in
the UK prior to their mass vaccination program. This study in UK looked at 373,402 participants aged ≥16 years who had mass swabbing (even when asymptomatic after vax) Dec 1, 2020-April 3, 2021. In fact, 1,610,562 PCR swabs as vax rolling out.
medrxiv.org/content/10.110…
Whether AztraZeneca (which is like J&J in being an adenovirus/DNA vaccine) or Pfizer (mRNA vaccine), symptomatic infection massively reduced after even 1 dose and importantly so was asymptomatic infection with CT<30 on PCR (at which point extremely hard to transmit).
So, by incorporating CT thresholds into their PCR analyses, they really show us the power of the vaccines in limiting the ability of a vaccinated person who has virus in their nose to transmit to anyone else in this large study. See
science.sciencemag.org/content/370/65…
This is likely why UK now has <200 people in the hospital with COVID-19 in a country of >66 million.
ourworldindata.org/grapher/uk-dai…
Which is why the UK has downgraded the status of the COVID-19 epidemic to endemic (low circulation of cases; not causing high hospitalizations or deaths) as of today (even with country opening) at about 50% 1st dose (ourworldindata.org/covid-vaccinat…)
news.yahoo.com/covid-pandemic…
And at 62% rate 1st dose vax in Israel (ourworldindata.org/covid-vaccinat…), that country had 0 daily COVID-19 deaths for 1st time in 10 months (again with mingling, etc.) leading country to fairly conclude they will reach herd immunity without vaccinating children timesofisrael.com/israel-reports…
And when it comes to San Francisco & the definition of an epidemic versus endemic, with <10 people in the hospital now (900K people) with #covid19 after excellent vax rate (65% 1st dose), we can turn to true epidemic (3x as many OD deaths than covid here) nytimes.com/2021/04/23/us/…

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More from @MonicaGandhi9

Monica Gandhi MD, MPH Profile picture
23 Apr
Two amazing papers recently that show the power of the vaccination to "uncouple" cases from hospitalizations and also massively prevent severe disease. Fully vaccinated Houston, 96% effective at preventing hospitalization; 98.7% at preventing death
medrxiv.org/content/10.110…
Paper, NEJM shows that 2 symptomatic infections (both mild, variants) out of 417 after vaccination (with mass screening program of asymptomatic)-rate of 0.005% consistent with CDC data last week showing 0.005% symptomatic breakthroughs out of 77 million
nejm.org/doi/full/10.10…
The fact that the 2 participants in NEJM study had mild infection with variants is consistent with fact that T cell immunity is preserved across the variants with mRNA vaccination
biorxiv.org/content/10.110…
Read 9 tweets
Monica Gandhi MD, MPH Profile picture
22 Apr
Thanks Dr. McBride. I think laying out the evidence on why ceasing outdoor masking (except when at rallies or packed crowds) based on biology will help ease us back to normal, shows trust of the public & is nuanced/tiered messaging.
My key points are as follows: 1) People know when they are outside (!); 2) A study in Wuhan China with careful contact tracing shows 1 of 7324 infections seem to be connected with outside transmission (& no outbreaks);
onlinelibrary.wiley.com/doi/10.1111/in…; 2) A meta-analysis from UCSF shows
risk inside >20x more than outside; 3) Scoping review from University of Canterbury shows outdoor transmission rare, citing the opportunity costs of " impact on physical and mental health and wellbeing" not gathering outside.”canterbury.ac.uk/science-engine…
Read 4 tweets
Monica Gandhi MD, MPH Profile picture
21 Apr
Want to talk about INFLECTION POINT and how it looks like we have reached this in our country with hospitalizations at this vaccination rate & also turning the corner in Michigan. We discussed this first with Israel & I think "inflection point" with both hospitalizations & cases
will be different by country/state/region depending on degree of natural immunity there. This article in Nature from early on in the Israel roll-out: "You need to vaccinate much >1/3 of the population to really see a reduction in transmission", how much
nature.com/articles/d4158…
more probably depends on 1) natural immunity (surges before (CA has 38% of its population exposed); 2) degree of lockdown as you are vaccinating (UK more; Israel less; places in US variable); 3) maybe even what vaccine (?India). Paper from Israel (Fig)
nature.com/articles/s4157…
Read 15 tweets
Monica Gandhi MD, MPH Profile picture
20 Apr
This is true but I am VERY worried about India right now. My understanding is that vaccine capacity is not maximal because more raw materials are needed. India has called on the Biden Administration (ASlavitt) for help. Masks/distancing as much as possible in crowded conditions.
India has Covishield (AZ vaccine) + Covaxin (Bharat Pharm). I see from phase I/II trial of the Covaxin vaccine that cell-mediated responses were generated (although used IFN-gamma assay that Sputnik V used in their paper instead of direct measurement).
medrxiv.org/content/10.110…
However, reason worried about Covaxin is that we have not seen phase 3 clinical trial results yet except in press release; would love to see peer reviewed publication (does anyone know status?). Covaxin is a whole inactivated viral vaccine like Sinovac
economist.com/graphic-detail…
Read 7 tweets
Monica Gandhi MD, MPH Profile picture
20 Apr
Will we be able to achieve herd immunity and at what level vaccination? I believe we will but I don't know at what % vaccination though I suspect it could be 65-70%. Why?
1) Achieving herd immunity with a vaccine is dependent on its effectiveness; the mRNA vaccines are more
effective than we dared hope with 100% efficacy at 6 months per Pfizer data and amazing CDC breakthrough data showing (with ongoing cases), of 77 million fully vaccinated against COVID-19, ~5,800 infections (0.008%) – 0.005% symptomatic (29% asymptomatic)
pfizer.com/news/press-rel…
2) Study from Israel shows children do not need to be vaccinated to massively reduce transmission in this group. Just vaccinating adults >16 years brings down infections among children substantially (every 20 point increase adults; halves in children)
medrxiv.org/content/10.110…
Read 6 tweets
Monica Gandhi MD, MPH Profile picture
19 Apr
@DLeonhardt article today NYT illustrates what @drlucymcbride, I & so many others discussing: a fear of normal or even following simple March 8 CDC guidelines that vaccinated people can get together without masks/distancing due to irrational fear.
nytimes.com/2021/04/19/bri…
"Fortunately, [fear] also curable. The vaccines have nearly eliminated death, hospitalization and other serious Covid illness among people who [got] shots. .vaccines have also radically reduced chances that people contract even a mild version of Covid or can pass it on to others"
Even acclaimed experts like @ashishjha realized how "awesome" it was to meet friend for drink unmasked 2 months (!) after his last shot. My advice for society on this as MD who talks to patients about irrational fear all time?
1) Leaders like President Biden? Model behavior like
Read 7 tweets

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