Long-haul risks drive home importance of vaccination

A large, population-based study published in Nature highlights COVID-19’s real long-term threat to our lives.

Long-haul COVID-19 patients face significant health threats, including a higher risk of dying for as long as six months after catching the virus, according to the study that examined more than 87,000 COVID-19 patients and nearly 5 million control patients in a U.S. database. In addition, researchers analyzed the subset of 379 diagnoses of diseases possibly related to COVID-19; 380 classes of medications prescribed; and 62 laboratory tests. To understand the long-term effects of more severe COVID-19, the researchers harnessed Veterans Health Administration data to conduct a separate analysis of 13,654 patients hospitalized with COVID-19 compared with 13,997 patients hospitalized with seasonal flu (a well-known, well characterized respiratory viral illness). All patients survived at least 30 days after hospital admission, and the analysis included six months of follow-up data. 

This subset of data analysis showed that those who had contracted COVID-19 fared considerably worse long term than those who had influenza. COVID-19 survivors had a 50-per-cent increased risk of death compared with flu survivors after six months. The extent of the risk of disease and death and the extent of organ system involvement are far higher than other respiratory viruses such as influenza.

A recent study published in CMAJ analyzed seven hospitals in the Toronto area and also found that patients with COVID-19 had a greater risk of death and ICU admission and longer hospital stays than patients with influenza.

Furthermore, compared with the general population, COVID-19 survivors had just over a 260 per cent increased risk of death over the following six months. In the non-infected population, excess deaths were estimated at eight people per 1,000 patients at the six-month mark. Among patients who were ill enough to be hospitalized with COVID-19 and who survived beyond the first 30 days of illness, there were 29 excess deaths per 1,000 patients over the following six months. According to the research, some of these later deaths are not necessarily recorded as deaths due to COVID-19, suggesting that the official numbers are only the tip of the iceberg in terms of the total pandemic death toll.

Further, long-haul COVID-19 patients also have a much higher long-term chance of illness, and not just respiratory illnesses: higher rates of stroke and other nervous system ailments; mental health problems such as depression; onset of diabetes; heart disease and other coronary problems; digestive disorders; kidney disease; blood clots; joint pain; hair loss; and general fatigue.  

Unfortunately, the general population’s understanding of this crisis still seems to be worryingly low. We have invested millions of dollars in communicating the immediate risks via public health messaging, but given the long-term consequences, have we communicated how dangerous it is to disregard, disrespect and undermine the power of our key tool against COVID-19? Rare blood clots related to vaccination should not be a deterrent. According to the latest data, 1.9 cases of these distinctive clotting events have occurred per one million people vaccinated (32 cases of venous thromboembolism among 17 million AstraZeneca vaccinations in Europe and the U.K.) The real risk? 0.00019 per cent of all doses administered. This rare clotting risk must not overshadow the benefits of COVID-19 protection.

The Public Health Agency of Canada, the European Medicines Agency, and the American Heart Association/American Stroke Association, the U.S. Centers for Disease Control (CDC) and the Food and Drug Administration, among others, have all concluded that the risk of unusual blood clots is extremely low and have asserted that the benefits of the vaccine outweigh the very rare risks.

The key is communicating to patients how to look out for a “two-in-a-million” side effect. The American Heart Association has cited the list of potential symptoms that could occur up to two weeks after vaccination – blurry vision, fainting, sensory changes, seizures, leg pain or shortness of breath.

Our physicians are well capable of diagnosing and treating blood clots early, effectively and efficiently. New clinical guidelines advise clinicians on what anticoagulation medications should be used to treat this condition. More importantly, we have a better understanding of the clinical data, prevalence, specific symptoms and the population at risk.

The U.S. CDC study based on real-world data efficacy on vaccines contains no surprises and plenty of reassurances: Pfizer-BioNTech or Moderna vaccines were 94 per cent effective against hospitalization among fully vaccinated adults and 64 per cent effective among partially vaccinated adults aged 65 or older in a multistate network of U.S. hospitals in January-March.

A recent real-world study from Scotland found that Pfizer’s vaccine was 91 per cent effective against hospitalization at 28 to 34 days following vaccination.

Interestingly, emerging new real-world data indicate that both the Pfizer and AstraZeneca vaccines cut the spread of symptomatic COVID-19 within a household by up to 50 per cent after one shot. In addition, AstraZeneca’s shot was 76 per cent effective at protecting against COVID-19 with symptoms for at least 90 days after the first shot. The study also found that AstraZeneca’s vaccine was 88 per cent effective against hospital admissions. These data suggest that continuing to rapidly vaccinate Canadians will have a marked impact on hospitalization and might lead to commensurate reductions in post-COVID-19 conditions and deaths.

In public health, we stress the importance of prevention. Staving off serious health issues related to this never-ending pandemic is of the utmost importance. Therefore, it is necessary to use the evidence of long-term risks to highlight the real dangers of COVID-19 and encourage all Canadians to be vaccinated and protect themselves, their loved ones and their community from potentially devastating short- and long-term health effects. 

Given that the burden of long-haul COVID-19 is substantial, the lingering effects of this disease will reverberate for many decades.

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Ediriweera Desapriya


Ediriweera Desapriya is a research associate in the Department of Pediatrics, Faculty of Medicine, University of British Columbia.

Parisa Khoshpouri


Dr. Parisa Khoshpouri is a research associate in the Department of Radiology, Faculty of Medicine, University of British Columbia.

Kamal Gunatunge


Kamal Gunatunge is a senior lecturer in the Department of Pharmacology, Faculty of Medicine, University of Sri Jayewardenepura Nugegoda, Sri Lanka.

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