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Zain Chagla Profile picture
Zain Chagla
@zchagla
Infectious Diseases Physician at St. Joe's Hamilton / Associate Professor at McMaster University. Views are mine alone and don’t reflect institutions.
Aug 14, 2022 • 5 tweets • 2 min read
Before this is sensationalized, 40 to 70 percent of people in series are hiv positive (and some of the negatives are at risk).

Prior smallpox vaccine campaigns didn’t have to deal with overrepresentation of hiv as a risk factor. 41 percent here:

nejm.org/doi/full/10.10…
May 1, 2022 • 5 tweets • 3 min read
The fast changing epidemiologic data of the hepatitis outbreak in children definitely makes finding an etiology hard. Here's the one thing I don't understand. The recent MMWR report notes the first few cases in Oct - Feb. Even the israeli data goes back to Feb 2021...
1/3 Wouldn't the paedatric transplant networks be raising the alarm in the USA in 2021 - given 2 of the Alabama cases needed transplant -- if this was happening across the USA - you'd expect some rise in liver transplant. Numbers are flat here @HHSGov
2/3
 optn.transplant.hrsa.gov/data/view-data…
Jan 5, 2022 • 8 tweets • 3 min read
Hearing a lot of folks turning down their booster as it's moderna. For those over the age of 50 - especially if medical conditions, please take the first dose you're offered. Firstly - this is the highest risk group for breakthrough infections leading to hospitalization
1/ Omicron is coming and breakthroughs unfortunately will be the norm. 2 doses are protective, but three doses in higher age groups will offer more protection for severe disease. Add to this many will be infected in the next 2-3 weeks, delaying minimizes any benefit.
2/
Jan 3, 2022 • 4 tweets • 1 min read
Just to get a sense of the numbers - there are around 4800 active cases in the city of Hamilton. We are likely diagnosing 1 in 7 to 1 in 10 given all the testing issues.

This roughly translates to 6 to 9% of the city that has COVID.

1/ This isn’t meant to be scary - it’s having impacts on healthcare Human Resources as healthcare workers live and work in the same communities.

But with an reproductive rate of 1.7 and a short generation time, we may be over 50% soon in the next week or two.
Oct 31, 2021 • 8 tweets • 2 min read
A booster campaign should focus on local data driven highest risk groups. What does Ontario show
1. Vaccines seem to preventing infections pretty well across all age groups, despite people saying they’re waned to nothing 2. Certain groups - particularly over 70 are at the highest risk of a breakthrough. Their risk is still lowered by the fact they’re at lower risk by getting COVID and still reduced complications. Still this is the appropriate target for a third dose given complications
Oct 5, 2021 • 7 tweets • 4 min read
A new study in the lancet suggests vaccine efficacy falls to 47% for ALL COVID-19 by 4 months, but what really counts - hospitalization is still preserved at over 88% prevention. One major issue I can note below...
thelancet.com/journals/lance… Looking at prior COVID infected (which the data cutoff Dec 14 2020) - only about 2% captured by prior PCR, and a few by serology. Some of this is probably lack of data through KP...
Jul 20, 2021 • 7 tweets • 3 min read
PH Ontario reports on vaccine breakthroughs released yesterday. Few caveats to the report but really showing how different this disease is post vaccine
1. New cases represented by unvaccinated and partially vaccinated (see right of this image) 2. Around 1900 breakthrough cases. Half of those asymptomatic - likely under diagnosed (outbreak) but unclear how clinically relevant given lack of symptoms. Still relatively few cases in relation to the pandemic - even recently
Jun 26, 2021 • 6 tweets • 2 min read
A Thread of why COVID-19 is a different disease in fully vaccinated individuals

1) 7 deaths and 14 hospitalizations in long term care in Ontario during a third wave which brought our health systems to overwhelming clinical needs

15 total symptomatic deaths of COVID-19 in Ontario of people that were fully vaccinated. Compared to 4000+ deaths over that interval.
May 6, 2021 • 4 tweets • 2 min read
This @NEJM paper suggesting 30% efficacy of the vaccine against B117 in Qatar is making the rounds. Really nice design for post 2nd dose vaccination, but the do not include a time-lag for 14 days post first dose (at least I can see in the paper/supp) 1/3
nejm.org/doi/full/10.10… Why is this important - well - we know vaccines take 10-14 days to kick in. So judging efficacy based on those first 10-14 days doesn't make sense. From Ontario data over 2/3 of breakthrough cases occur in this period.
2/3
May 5, 2021 • 4 tweets • 1 min read
Report from Ontario on Vaccine breakthroughs amongst first 3.5 mill
-0.06% of people partially or fully vaccinated had a breakthrough
-2/3 of those under 2 weeks
-only 3.9% of breakthroughs (were 7 d post second dose)
-B117 still the major cause of breakthrough - the odd others -155 hospitalizations amongst "breakthrough cases" amongst 3.5 million doses. Only 6 (all >60) amongst fully vaccinated
-49 deaths amongst partially vaxxed, 0 amongst fully
-all vaccines seem same ballpark for breakthroughs (0.04 to 0.1%)
Apr 25, 2021 • 5 tweets • 4 min read
#CovidIndia Am hearing many doctors telling patients to get plasma (blood from survivors) for their sick loved ones. This is NOT a useful therapy and should not be considered as part of the standard of care for COVID-19. Please see explanation and share:
1/ Original study was in India - 464 adults - death was unchanged with plasma vs. no plasma.
bmj.com/content/371/bm…
2/
Apr 24, 2021 • 5 tweets • 1 min read
Many of us in 🇨🇦 are seeing something in healthcare we've never seen before and it's scary. While we need to communicate to the public and make them a stakeholder in this, it's important to realize that fear and shame are no longer effective strategies.
1/ It's been 15 months into the pandemic. People are either making risky decisions because they choose to (people know how to physically distance, mask, etc by now) or they're put into situations where that isn't possible. There isn't a knowledge gap for the former.
2/
Apr 15, 2021 • 6 tweets • 2 min read
The risk of getting COVID and being hospitalized is at its highest Vax are here to help us decrease transmission, BUT most potent role is reducing your risk of hospitalization and death after 2 weeks - all 3 available in Canada after the first shot. Numbers below 1/ Pfizer

Clincal trials - ZERO severe cases post first dose.

Real life
Israel - 74% reduction in hospitalization 14 days post first dose as compared to unvax
Scotland - 60% reduction day 14 - up to 84% day 28 (huge amount of B117)
2/
Apr 11, 2021 • 4 tweets • 2 min read
There's a lot of stress and grief - and it needs to be balanced with hope. Life will return to normal. Yes there is turbulence and we're facing the most critical point in the pandemic, but with vaccines, there is an expiry date to our fears 1/

bit.ly/2QfXjy0 With cases near the peak they have been for the entire pandemic, the vaccines in our most vulnerable have had profound effects. We should be nearing 150 deaths a day nationally, instead we're sitting around 30. Still too many, but 100+ deaths a day saved by vaccines. 2/
Mar 15, 2021 • 4 tweets • 1 min read
I know people are concerned about astrazeneca and the clotting issue. These types of things are difficult to tease out, if it's an incredibly rare reaction vs. natural rate. However, this is the power of phase IV (post marketing) surveillance 1/6 Imagine you literally followed every adult in the New York City Area for 4 weeks - all 15 million or so of them. Followed them to see what happened to them. A percentage will have things occur - car accidents, hit by lightning, and develop blood clots. 2/6
Mar 12, 2021 • 6 tweets • 2 min read
Many people quote 62% efficacy in the AstraZeneca trial. This is based on a pooled analysis of two trials looking at two dosing regimens, which varied. The standard dosing regimen was the one chosen for publication. My analysis here
acpjournals.org/doi/abs/10.732…
1/n Issue with these vaccines is the way they're packaged. They take a modified chimpanzee adenovirus (that can't replicate) and add the DNA of the spike protein. Once in the cell uses it's machinery to make this protein and trigger an immune response (similar to mRNA vax) 2/n
Mar 11, 2021 • 8 tweets • 2 min read
Can we stop the narrative please that a prolonged first dose strategy is going to breed super variants. The immune system is NOT like antibiotic resistance. 1/n Antibiotic resistance is due to bacteria changing their proteins, adding pumps, or secreting enzymes to break down antibiotic chemicals that are meant to kill bacteria. These sometimes are already established, picked up from other bacteria, or emerge over time. 2/n
Mar 7, 2021 • 12 tweets • 4 min read
I know many are a bit on the fence (as with me) about moving our vaccination plan to a 4 month lag between doses. The balance is the evidence at two months shows protection albeit suboptimal - but we are taking a gamble at 4 months plus long term response. 1/n But I'm coming around to it. This is driven by a supply shortage of vaccine, and I get it. As with playing poker, you can blame the dealer for your hand, or you can try to make the most of it by strategy/bluffing etc. We're choosing to get the most of what we have. 2/n
Feb 24, 2021 • 11 tweets • 3 min read
FDA Data set around J+J Vaccine Released. This is the hopeful vaccine that will change the world - knowing that a) storage requirements are amazing (2-8 degrees) and b) single dose regimen, which in LMIC is going to be great for mass vaccination. Some highlights Efficacy analysis was slightly different - primary was moderate to severe (see below) - however some exploration of any COVID-19.
Feb 6, 2021 • 5 tweets • 2 min read
One thing to watch for the weeks to come. As B117 is rare for now, it’s emergence really does give us a better sense of the epi links occurring around us. With so much circulating COVID normally it’s hard to necessarily pick out where it came from So if I get B117, there’s only a certain number of cases in the community. With enhanced contact tracing it should be easier to highlight the chain of transmission given they will all be B117. Similarly outbreaks have a common link.
Jan 16, 2021 • 10 tweets • 2 min read
I've been thinking more about sustainability in the face of this pandemic. As a vaccine rolls out more and more, how do we create processes now that are sustainable for the future year to come, to improve the way we deal with a mixed immune population of COVID moving to future1/ 1. Rapid tests are a part of it. Put rapid tests at every assessment center. Patients with symptoms get a rapid test and PCR - and allow rapid test neg folks out of iso until PCR returns (with some exception for those in vulnerable settings or healthcare) 2/