Covid Study References

I sometimes write without linking to studies because I've posted all the studies so many times already, but here's a bunch of useful ones when evidence is necessary.

THE PROBLEM:

Covid isn't a cold at all; it's a vascular disease (affecting the circulatory system) that produces microclots, which can lead to blood vessel damage, strokes, and loss of brain tissue (Frontiers in Microbiology, 2021, Journal of Thrombosis and Haemostasis, 2022, Cardiovascular Diabetology, 2022). Heart disease risk soars after even a mild case (Nature 2022), as well as the risk for heart attacks (Journal of Medical Virology, 2022). Dr. Funmi Okunola explained how Covid causes hypercoagulability, which damages the endothelium, increases strokes, pulmonary embolisms, and deep vein thrombosis, and Professor Danny Altmann explained how clearly mild Covid can be seen to affect the brain in a 2024 video. After an acute case, it hibernates in the body (like chicken pox and HIV), then can cause worse effects years later: the "SARS-CoV-2 spike protein accumulates and persists in the body for years, especially in the skull-meniges-brain axis" (Cell Host & Microbe, 2024). We still know relatively little about Covid, how long it can last, and all the things it can do to the body. HIV started out looking like a bad flu lasting a few weeks, then ten years later, people started dying of AIDS. Nobody knows for sure what the 2030s will look like. It currently still kills more people than car accidents, even as it adds to the number of collisions (Neurology, 2024). It might be wise to continue to take precautions. 

59% of SARS-CoV-2 transmission is from people who don't have any symptoms: 35% from people who are presymptomatic and 24% from people who are carrying it without developing symptoms, like Typhoid Mary (JAMA, 2021), so only masking when around people who are visibly sick, like my doctor does, avoids less than half of the potential transmission in the room, especially in primary health care. 

Viruses spread over many feet and hang in the air (think of it like cigar smoke - you can smell it from across a room, and you can tell is someone was smoking in the room before you got there): "Transmission was also found to occur from particles remaining suspended in the air and travelling longer distances, hence the benefit of wearing masks" (Health Canada, 2025). It means someone could be coughing up a lung in a store, then leave, and then you show up to an almost empty shop that feels very safe, yet the air is chock full of the virus. A general rule of thumb of always masking in public buildings means no longer having to think about risk calculations or wonder who was there beforehand.

There's no limit to how many times you can get Covid, and each infection increases risk of serious illness. Anyone can get Long Covid, even young, healthy people who eat well and exercise (Durham County Public Health, 2025). It can cause long-lasting cognitive dysfunction in your adults at least two years after infection affecting verbal working memory and cognitive reaction time (Life, 2025). Cognitive disabilities spiked since 2020, and there's no other plausible explanation for the scale and timing of this trend. In Olympic athletes, 64% of those infected had ongoing limitations in their sport (Journal of Exercise and Sport Research, 2025). 

It's decimating healthcare workers, adding to the healthcare burden from both ends. In the UK, 18% of healthcare workers were off work due to Covid. Some claim their lives have never been the same since this first infection (Medscape, 2025). In BC, over 18% of people have Long Covid symptoms causing work productivity issues compared to the burden associated with multiple sclerosis and rheumatoid arthritic, despite that Covid is preventable (CIDRAP, 2025).

Kids definitely get it too. One study estimates 15% of kids have Long Covid, but doctors are missing the signs (Rutgers, 2025). Another huge study pegged it at 14-20% (Journal of the AMA, 2024). A newer study found that blood samples may find biomarkers that can better diagnose Long Covid which might help diagnosis (CROI, 2025). In one study on children, they found inflammatory markers three months after an acute infection, which suggests damage to the immune system (CROI, 2025). Long Covid surpassed asthma as the most common chronic condition in American kids (JAMA Pediatrics, 2025).

It causes a lot of problems in the brain. I've compiled many studies on Covid's effect on the brain and continue to add to them there. 

THE SOLUTIONS:

Nothing works perfectly, so we have to follow that Swiss cheese model of doing several things at once to get to zero risk. I tend to trust my N95 and not look into any of the others things in public buildings, but I have a CR box in my house. 

Masks work (i.e. well-fitting respirators like N95s/FFP3s, not medical masks or cloth masks) (Clinical Microbiology, 2024), which is explained in plain English here. They're not just a filter, they also trap the virus using inertial impaction, interception, and electrostatic attraction (which is why you should throw out a mask if it gets wet). Here's an explainer from Dr. Jeff Gilchrist, and a two-minute video from Professor Trish Greenhalgh at Oxford.

Clean air helps (CR boxes and ventilation): "Individuals exposed to CO2 concentrations greater than 800 ppm were more likely to report mucous membrane or respiratory symptoms (Health Canada, 2025). Upper room UVGI would kill any viruses, and could be part of hospitals and school either installed near the ceiling or in the HVAC (EPA, 2025). It's expensive, but it would be an absolute game-changer.

Vaccines help reduce the effect of the virus, but you can still get it and spread it, and vaccine effectiveness wanes in a few months because the virus mutates so quickly (because there's so much spread -- it needs to get in a host body to mutate). Getting a vaccine "remains safe and strongly recommended during pregnancy" (Society of Obstetricians and Gynaecologists, 2025).

Rapid tests have a lot of false negatives in the first five days, so you can be contagious and show a negative. But by day 6, there's usually enough of it to be more accurate. They still suggesting also testing on day 7 to be sure. A positive line is almost always positive.

There's little access to meds that help (we have to be over 65 to get Paxlovid in Ontario), but in the Netherlands they've seen 75% of cases have viral clearance within 28 days with nirmatrelvir/ritonavir (CROI, 2025), and Pfizer is testing Ibuzatrelvir (but it might still not be available to anyone under 65) (C&EN, 2025). I'm less excited by nasal sprays or any supplements these days, but I'll still do the spray (just Betadine until Azelastine's approved in Canada) if I'm going to be in close contact with people who don't generally mask in public. 

Also check out Dr. Sean Mullen's downloadable factsheet and Dr. Lucky Tran's explainer of why it's still a good idea to avoid getting Covid. Both have tons of links to studies. The Delphi Consensus is older, but that just shows we knew all this (Nature, 2022).

I've landed on masks being most vital because it's all that's within our control. Wearing an N95 does a very good job of preventing getting a virus, and it also prevents spreading a virus if you have one and don't know about it, AND, with fewer hosts, it will reduce how quickly the virus mutates which will extend vaccine effectiveness.