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Sabina Vohra-Miller Profile picture
@SabiVM
Jan 21 • 7 tweets • 3 min read • Read on X
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Does Long Covid alter the immune system?

New evidence suggests this may indeed be the case.

Study summary in collaboration with @LizMarnik
1/7 Image
This is the study we attempt to summarize:


2/7 nature.com/articles/s4159…
Research is slowly starting to find out what processes may be behind some of the symptoms those with long COVID experience. Image shows screenshot of actual article
Samples were collected via a prospective observational study that enrolled individuals with prior SARS-CoV-2 infection with and without long COVID symptoms
3/7 Participants were enrolled in a prospective observational study that enrolled individuals with prior SARS-CoV-2 infection with and without long COVID symptoms. Samples were collected from participants at 8 months post infection before any participants were vaccinated or reinfected. Results were compared between those with long COVID symptoms to those without.
Those with Long COVID exhibited systemic inflammation and immune dysregulation

There was improper crosstalk between the cellular and humoral adaptive immunity in those with long COVID
4/7 Those with Long COVID exhibited systemic inflammation and immune dysregulation There was improper crosstalk between the cellular (eg: T cells) and humoral adaptive (eg: antibodies) immunity in those with long COVID Individuals with long COVID had: increased numbers of COVID-19 specific CD4+ T cells that were able to migrate to inflamed tissues exhausted COVID-19-specific CD8+ T cells higher levels of COVID-19 antibodies mis-coordination between COVID-19-specific T and B cell responses
These findings provide further evidence that there are immune system differences in long COVID that is likely contributing to their symptoms.
5/7 Researchers also saw significant increases in the following in those with long COVID (LC) compared to those without (R): TFH cells T regs CD4 central memory T cells These findings provide further evidence that there are immune system differences in long COVID that is likely contributing to their symptoms.
Limitations:
- Small small size
- long COVID is an umbrella term so may not apply to every long COVID patient
- data was only from 8 months after infection, need longer duration studies
6/7 Small small size, therefore validation of results in larger cohorts is necessary. We are starting to realize the long COVID is an umbrella term used to group those with varying post COVID conditions. So this may not apply to every long COVID patient. This is why we need more research and better diagnostics. This data was only from 8 months after infection. It would be helpful to see if these results change over time and how vaccination or repeat infection may impact these findings.
Final thoughts:
- This data seems consistent with the theory of persistent viral reservoirs in long COVID
- The misalignment b/w cellular & humoral adaptive immunity may explain inflammation & debilitating clinical symptoms in those with long COVID
7/7 This data seems consistent with the theory of persistent viral reservoirs in long COVID. This causes ongoing stimulation by viral antigens which keeps the immune system active. The observation of higher COVID-19 antibody levels in those with long COVID supports this. The misalignment between cellular and humoral adaptive immunity in those with long COVID may explains the inflammation and clinical symptoms associated with this debilitating condition. More studies with larger cohorts are needed to see if this is found in all long COVID patients and to look at how these results may changes...

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More from @SabiVM

Sabina Vohra-Miller Profile picture
Aug 27
Canada specific FAQs on the updated Covid-19 vaccines
🧵 1/8 Image
Options available:
Pfizer and Moderna: both of these will target the KP.2 variant.

The mRNA vaccines are anticipated to be available around the middle of October.

Unfortunately Canada did NOT purchase any Novavax for 2024-2025.
2/8 Options available in canada Health Canada has received submissions from both Pfizer and Moderna for the updated COVID-19 vaccines. Both of these will target the KP.2 variant. The mRNA vaccines are anticipated to be available around the middle of October. Currently, KP.3.1.1 is the dominant COVID-19 variant, overtaking parent linage of KP.3 and KP.2 variants. Unfortunately Canada did NOT purchase any Novavax for 2024-2025. This is partially because of lower uptake of this vaccine, and also because Novavax had already committed to vaccines targeted towards the JN.1 variant (predecessor of...
NACI Recommendations
An updated 2024-2025 COVID-19 vaccine should be offered as a strong recommendation to:

- All adults 65 years of age or older
- Those 6 months of age and older at higher risk of exposure or illness.
3/8 NACI Recommendations An updated 2024-2025 COVID-19 vaccine should be offered as a strong recommendation to: All adults 65 years of age or older Those 6 months of age and older: Residents of long-term care homes and other congregate living settings Have underlying medical conditions that place them at higher risk of severe COVID-19 Who are pregnant In or from First Nations, Métis and Inuit communities Members of racialized and other equity-deserving communities People who provide essential community services
Read 8 tweets
Sabina Vohra-Miller Profile picture
Jul 22
We are in a summer COVID surge and this has lead to many questions! In this post @LizMarnik and I share things to consider to protect yourself, what we both do & consider in our own actions and recommendations for others to help make society safe & equitable for all.
🧵 1/8 WE ARE IN A COVID SURGE. WHAT THINGS SHOULD YOU CONSIDER?
Why are cases increasing? Mostly due to new variants, summer behaviours such as travel and really, because that’s just how pandemics work.
2/8 Why are cases increasing? 1. New variants: KP.2 and KP.3 make up a large percentage of the COVID-19 cases right now. These are two new variants that have differences compared to prior variants. This means that prior infection and vaccination doesn't give as much protection for these newer variants. Fall vaccines will target JN.1 (Novavax) or KP.2 (mRNA) but these are not yet available. 2. Summer behaviors: As the weather warms, people move indoors to air conditioned indoor settings. Summer also brings with it things like large parties and gatherings, new settings for children like camps and...
There are lots of things you can do to stay safe:

Mask, esp indoors. Test. Be in well-ventilated areas, outdoors preferred, stay home when sick and vaccinate.
3/8 How to stay safe during a surge? Mask: Especially when indoors and in crowded areas. Wear a well-fitted respirator. Test: Keep tests on hand for when you have symptoms. Remember while it is allergy season for many, symptoms can overlap with viral infections. Be in well-ventilated areas: Choose outdoors over indoors. Open windows, run HEPA filters & use CO2 monitors indoors. Higher CO2 means there is not as much ventilation therefore risk is higher. Eat outdoors: Choose a restaurant patio, a picnic at a park or if your kid goes to camp, request they be able to eat lunch outside Keep your ger...
Read 8 tweets
Sabina Vohra-Miller Profile picture
May 9
So much disinformation on AstraZeneca's announcement re: withdrawing their COVID-19 vaccine, so I thought I should go back and review the timelines of what occurred in Canada.

Hang on, because this is going to be a wild ride. Thread, and a long one. /1
theguardian.com/business/artic…
Image
AstraZeneca's COVID-19 vaccine was first approved in Canada on Feb. 26, 2021. /2
cbc.ca/news/politics/…
Image
In Canada, it was first only recommended to be used in adults 64 and younger. This is because the initial study results were too limited to allow a reliable estimate of vaccine efficacy in individuals 65+. /3
ctvnews.ca/health/coronav…
Image
Read 24 tweets
Sabina Vohra-Miller Profile picture
May 8
New post on Rapid Antigen Tests. Will post the entire thread here instead of just a link, given importance.

A master thread with current data: key concepts, which brands are more sensitive, tips to improve sensitivity & important considerations. 1/7 RAPID ANTIGEN TESTS A master thread with current data: key concepts, which brands are more sensitive, tips to improve sensitivity and important considerations.
Recent CDC MMRW Report found overall sensitivity of RATs was 47% compared to PCR.
The peak percentage of positive RAT was 59.0% occurred 3 days after onset of symptoms.
Highest on days when fever was reported, lowest on days when no symptoms were reported. 2/7 RAPID ANTIGEN TESTS - OVERALL SENSITIVITY Recent CDC MMRW Report assessed the performance of Rapid Antigen Tests (RATs) compared to PCR. The study collected data from a household transmission study between Nov 2022 - May 2023. Overall sensitivity of RATs was 47% compared to PCR. The peak percentage of positive RAT was 59.0% and PCR was 83.0%, which occurred 3 days after onset of symptoms. Highest sensitivity for RATs was on days when fever was reported, and the lowest sensitivity was on days when no symptoms were reported.
Overall QuickVue and Flowflex had the highest sensitivity. Special mention for Australian Fanttest. Several commonly used RATs performed extremely poorly.
3/7 CERTAIN BRANDS ARE MORE SENSITIVE Several studies on Omicron-related variants have been conducted to assess the sensitivity of various brands of RATs Overall QuickVue and Flowflex had the highest sensitivity. Special mention for Australian Fanttest. A new study just published looked at 10 commonly found RATs in Canada. Of these, the three that were best performing wer that were best performing were: BTNX Cassette (spit) Flowflex Medsup The worst performers were: BTNX, PCL, PanBio, SDBiosensor, StandardO A US-based study looking at common US tests found the following sensitivity: Health 73...
Read 7 tweets
Sabina Vohra-Miller Profile picture
Apr 25
Avian Flu:
Current situation, context and what you need to know 1/8 Image
AVIAN FLU - A BRIEF HISTORY:
Highly Pathogenic Avian Influenza (HPAI) is caused by Influenza A H5 and H7 viruses. The current highly infectious strain of Avian Influenza that is spreading is the H5N1.
H5N1 is not new. 2/8 AVIAN FLU - A BRIEF HISTORY: Highly Pathogenic Avian Influenza (HPAI) is caused by Influenza A H5 and H7 viruses. The current highly infectious strain of Avian Influenza that is spreading is the H5N1. H5N1 is not new. It was first detected in chickens in Scotland in 1959; however that strain was very different from the current version of H5N1 which underwent a significant evolution around 1997. Sporadic cases and outbreaks have resulted in hundreds of human cases of the H5 Avian influenza virus, particularly the H5N1 subtype and predominantly from direct contact with infected birds in comme...
Currently we have an outbreak of the subtype H5N1 clade 2.3.4.4b.
There are 33 outbreaks across 8 states in cattle reported in USA. None in dairy cattle in Canada, CFIA monitoring closely.
This degree of spread outside of birds & poultry is unprecedented & concerning.
3/8 Currently we have an outbreak of the subtype H5N1 clade 2.3.4.4b. There is some data to show that this strain requires a lot more direct contact for spread to humans than H7N9. Avian flu has been spreading amongst wild birds, poultry and as of recently, dairy cattle. It is now estimated that it has been spreading in dairy cattle since late 2023. As of April 21st, there are 33 outbreaks across 8 states in cattle reported in the USA alone. Avian flu has not yet been discovered in dairy cattle or other livestock in Canada; however, CFIA is currently on high-alert and monitoring closely. In add...
Read 10 tweets
Sabina Vohra-Miller Profile picture
Apr 2
In science & esp medicine, risk is a tricky thing to contend with - besides of course being a mathematical one - and involves many considerations in order to have a more fulsome understanding.

In this post @LizMarnik and I attempt to explain these concepts. 1/9 Let’s talk risk What is relative vs absolute risk? What is cumulative risk? Why do these terms matter? And how do these impact our lives?
In simple terms, risk is the probability of an event occurring. In statistical terms, the risk of an event occurring is simply defined as its probability.
2/9 WHAT IS RISK? In simple terms, risk is the probability of an event occurring. In statistical terms, the risk of an event occurring is simply defined as its probability. Absolute risk of a disease is your risk of developing the disease over a time period. Relative risk is used to compare the risk in two different groups of people. What does this mean?
Take a fictitious disease - AhCrap. Risk of dying due to this is 2/million & using GoodStuff tx can reduce risk to 1/million.
While relative risk reduction is 50%, only one less person out of 1M w AhCrap are saved by GoodStuff, making absolute risk reduction fairly small.
3/9 ABSOLUTE VS RELATIVE RISK Take a fictitious disease, say Disease AhCrap. The risk of dying due to AhCrap is two in a million - ie, for every one million people who suffer from AhCrap and are not treated, two out of these one million people will die. Let's say we have a way to treat this AhCrap disease, using GoodStuff treatment. This treatment can reduce the risk of dying from two in a million to one in a million. Because the risk of dying decreased from two in a million to one in a million, the relative risk decreased by 50%. However, the absolute risk only changed from 2/1,000,000 to 1/1,...
Read 9 tweets

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