Vaccine hesitancy in the age of COVID-19

As the long-awaited COVID-19 vaccines are being administered to the Canadian public, a significant proportion of the population remains hesitant to get their injections. Vaccines generally have minor amounts of negative publicity; however, since the COVID-19 vaccines were developed at an accelerated rate, people are afraid that long-term side effects have yet to be revealed. This has led, in some cases, to the exaggeration of side-effects and a decreased proportion of the population getting vaccinated. In Ontario, for instance, only 70% of long-term care workers chose to be vaccinated[1], citing hearsay evidence of paralysis and incapacitation following vaccination[2].

Vaccine hesitancy harms not only those who do not get vaccinated, but also those to whom they might spread the virus – including vulnerable populations, such as those in long-term care homes and hospitals. This is particularly a concern with respect to the high rate of vaccine hesitancy among healthcare workers[3], which has been exacerbated by the recent withdrawal of the ‘vaccinate or mask’ policy for nurses working in Ontario[4]. To help dispel these myths, this feature will describe misconceptions about general vaccine safety and side-effects, as well as the safety of the four approved COVID-19 vaccines (Pfizer, Moderna, AstraZeneca, and Janssen).

Reasons for vaccine hesitancy

A wide range of factors and social forces are responsible for vaccine hesitancy. These include misinformation from the scientific community (most notably Andrew Wakefield’s infamous paper linking autism to vaccines[5]), inaccurate and misleading reporting of spurious, weak, or rare temporal relationships to adverse health outcomes[6], misinformation campaigns on social media which distort anecdotes, and a general fear of needles and chemicals[7]. Though most public motives for avoiding vaccines are driven by misinformation, some reasons for refusal to be vaccinated are justified. For instance, live attenuated vaccines cannot be given to immunocompromised individuals, and people with severe allergies to certain vaccine components can suffer anaphylactic shock if administered vaccines which contain specific allergens. However, these exceptions apply only to a tiny fraction of the population (only 1 in 125 000 people have allergic reactions to COVID-19 vaccines)[8]. Distinguishing between misinformation and legitimate risks, and communicating that these risks – while real – are exceedingly rare, may help allay the fears surrounding vaccines.

To begin, Andrew Wakefield’s 1992 paper, published in the prestigious biomedical journal, The Lancet, described a causative relationship between the MMR (Measles, Mumps, and Rubella) vaccine and the onset of autism. It claimed to describe a mechanism by which the vaccine ‘caused’ autism – it supposedly caused symptoms resembling inflammatory bowel disease (IBD), which in turn led to changes in the brain that precipitated autism[9]. This claim, however, was scientifically invalid – most of the cases he studied saw the gut changes occur after the onset of autism, the mechanism of altered brain function had previously been refuted, and he was unable to find vaccine particles remaining in the tissues of any patients studied[10]. The paper was soon retracted from the journal[11], (as was his medical license) but the initial publication galvanized the anti-vaccine movement[12]. Since then, claims about severe and common vaccine side effects, including autism, have time and again been disproven. Despite this, the anti-vaxxer camp has continued to grow[13], and has drawn support due to sensationalized reporting and social media. For instance, a 2015 Toronto Star article on the “dark side” of the Gardasil human papillomavirus vaccine described rare and coincidental events in recipients of the vaccine. One example described how a teenager mysteriously died after receiving the vaccination but provided no supporting evidence that the vaccine was responsible for her sudden death[14]. Though the article was eventually withdrawn from the newspaper, it is illustrative of how media can distort anecdotes and generate fear among the lay population. Partly due to this public mistrust surrounding Gardasil, vaccination rates among youth have dropped from nearly 100% just a few years ago to less than 50% in Canada and other developed nations[15]. Like Wakefield’s paper, this highlights how misinformation can spread faster than information, and how damage due to misinformation is not easily undone.

Moreover, vaccine hesitancy is driven by fear of the unknown and the presence of ‘unnatural’ chemicals present in vaccines. Generally, these components serve as adjuvants, which are compounds required to stimulate a more potent immune response and induce long-lasting immunity. These include aluminum, polysorbate 80, and formaldehyde, among others[16]. The fear surrounding these compounds are often amplified by online anti-vaccine campaigns. For example, the popular anti-vaxxer webpage, “A Voice for Choice”, claims that aluminum is present in vaccines at “neurotoxic levels”, a false statement[17]. Though scientific evidence demonstrates that these components, at the concentrations present in vaccines, do not have negative side effects, some remain afraid that their children are being administered compounds which have long-lasting or unknown toxic effects[18].

Though the above misgivings about vaccines can be easily disproven, a more insidious source of doubt comes from complications or diseases that are documented in clinical trials following vaccinations. These are usually low-frequency autoimmune complications, such as paralytic Bell’s Palsy and Guillain-Barre syndrome, and some vaccinations are suggested to slightly elevate the risk for these conditions. For instance, in most years the Influenza vaccine elevates the occurrence of Guillain-Barre syndrome by 1 to 2 additional cases per one million individuals[19]. Though the statistical evidence suggests only minor differences, if any at all, these fears are cited by anti-vaxxers as ‘scientifically proven’ reasons why vaccines should not be used. What is omitted by these campaigners, however, is that Influenza infection carries a higher risk for Guillain-Barré syndrome – so much so that the flu shot actually lowers the overall risk of the disease[20]. Hence, a simple counterargument is that the diseases vaccinated against have far more severe and more frequent consequences than the vaccines.

COVID-19 vaccine side-effects

Despite the widespread impacts of the COVID-19 pandemic, the vaccines being distributed face a considerable degree of reluctance and hesitancy. This is a particular concern because vaccination is not only useful in protecting those who receive the shot, but in protecting the community at large via herd immunity. The proportion of people who need to be immune to achieve herd immunity ranges from approximately 60% to 80%[21],  but this may be difficult to achieve given that over 50% of Canadians express some reluctance to receive the vaccine shots[22]. As of May 2021, we have only achieved 50% vaccination rates in Canada and USA, yet daily vaccination rates are decreasing. In fact, some workplaces are considering paying people to receive their shots[23].

A recent paper noted that many of those who do not plan on getting vaccinated made this decision based on concerns about safety[24]. While it is true that vaccines have unsafe side effects, they are rare and in almost all cases minor, especially when compared to the risk of COVID-19 itself. Common side effects of the four[SC1]  presently approved vaccines (of which only three are available; Janssen vaccines have yet to arrive in Canada in large numbers) include local pain at the injection site, chills, fatigue, headaches, and fever[25],[26],[27],[28] and typically resolve within 1-3 days[29],[30]. There are some reports that the second shots of the mRNA vaccines (Pfizer and Moderna) can have slightly stronger symptoms, often resembling the flu, but these resolve within a few days[31]. When weighed against the risks of COVID-19 – both in terms of contracting the disease and spreading it to vulnerable populations – a few days of flu-like symptoms is comparatively minor. Nevertheless, there are some valid concerns associated with these vaccines.

Given that phase 3 clinical trials lasted less than a year, compared to the usual 1-4 years, alongside the fact that the Pfizer and Moderna vaccines are the first major use of mRNA vaccines, concerns about safety are understandable. However, phase 3 trials for the vaccines were conducted across tens of thousands of people, and safety data from the public distribution of the vaccines continues to be collected and monitored[32]. There remains a small possibility that there may be some long-term negative side effects, but this is unlikely since we would expect them to be foreshadowed by immediate or medium-term side effects, of which none were observed. Nevertheless, there some concerns about immediate adverse events are justified, in particular anaphylaxis and blood clotting.

Take severe allergic reactions, for instance, which a misleading news cycle has used to help fuel hesitancy. Uncommon anaphylactic reactions to the mRNA vaccines have occurred, and thus the fears surrounding them are not completely unfounded.[33]. News headlines, on the other hand, often insinuated that those with penicillin[34], peanut[35], and other common allergies should not take the vaccine at all. Even if the articles themselves were consistent with government recommendations, these sensationalized headlines can engender reluctance to take the vaccine, hurting individuals’ health and that of society at large. Furthermore, all vaccine recipients are monitored for a short period after vaccination to ensure their safety, given that most anaphylactic reactions occur soon after vaccination[36]. The CDC only recommends not getting the vaccine if a patient is allergic to polyethylene glycol or polysorbate, which is exceedingly rare[37]; those with common food allergies have no elevated risk[38]. Finally, if someone is concerned about a potential reaction, they should talk to their doctor, rather than consulting a potentially misleading online source.

Another legitimate concern is blood clotting following the AstraZeneca and Janssen vaccines[39]. Unlike the mRNA vaccines, these companies built their vaccines using Adenovirus vectors, and the immune responses which develop are slightly different. In particular, abnormal blood clotting was found in a very small fraction of patients aged 20 to 50, sometimes alongside a decrease in the levels of platelets[40]. This is referred to as vaccine-induced immune thrombotic thrombocytopenia or VITT[41]. Current evidence suggests that these events could be the result of the AstraZeneca vaccine, so fears of these events are valid – especially considering that they can be fatal. However, this is another rare effect – as of the time of writing, the European Medical Agency is investigating 86 suspected cases, which is a tiny fraction of the 25 million Europeans who have received this vaccine thus far[42]. Furthermore, the complication is concentrated in a particular demographic (women under the age of 60), so immunization strategies can further mitigate an already-low risk[43]. The Canadian government has paused the vaccine’s delivery to those under 55 out of precaution[44], but this recommendation does not solely reflect a consideration of the vaccine’s costs and benefits on its own. Instead, the NACI (the government body that made the decision) recommended the pause since the country has an excess supply of mRNA vaccines (Pfizer and Moderna), which do not come with this associated risk[45].

Thus, while government restrictions on vaccine recipients’ ages are justified, vaccine hesitancy in eligible populations is not. The risk of dying from VITT following vaccination (approximately 1 in 100,000) is far lower than the risk of dying from COVID-19 (roughly 1 in 50, extrapolating from Canada’s cases and deaths)[46], and the rate is so low that researchers are still debating whether it is statistically significant[47].

Alongside these valid concerns, hesitancy surrounding the COVID-19 vaccines is often amplified by claims with no scientific basis or facts that are presented without context. Social media has facilitated the spread of misinformation about side effects, particularly the vaccine’s impact on fertility and pregnancy. Due to standard clinical trial protocol, as well as ethical concerns, phase 3 trials of the COVID-19 vaccines did not enroll any pregnant women – therefore, the data collected thus far cannot conclusively assess the vaccines’ impacts on this demographic. However, several women enrolled became pregnant over the course of these trials, and there is no indication of any negative impacts in the data on these patients[48]. Moreover, there were some earlier concerns that the mRNA vaccines might interfere with the development of the placenta. A region on the spike protein resembles part of the Syncytin-1 protein, which is important for placental development, so some feared that antibodies against the protein could affect fertility. Further study of the vaccines’ mechanisms of action, however, clearly show that this does not occur[49]. In fact, both the American Society for Reproductive Medicine and the Royal College of Obstetricians and Gynecologists note that there is “no biologically plausible mechanism” for mRNA vaccines to affect fertility[50],[51]. Despite this, there are numerous reports of hesitancy attributable to this concern[52]. Once again, the spread of misinformation has led to fears and hesitancy that harm individuals and society.

In sum, while hesitancy around the COVID-19 vaccines is understandable, the risks associated with vaccination are far outweighed by its benefits. People will experience side effects rarely, and even then, they tend to be minor and short-lived. Severe allergic reactions and blood clotting are real side effects; however, they are even more uncommon. Moreover, Canadian regulations further minimize these risks – people are monitored for allergic reactions after getting their injections, and the use of AstraZeneca vaccines in those under 55 has been paused. Finally, many claims made in news reports and social media – for instance, those surrounding food allergies or fertility – are simply not valid given the data available. Altogether, these fears – whether valid, exaggerated, or misinformed – should be publicly addressed and placed into the context of a far more deadly disease to maximize the public health benefits of these vaccines.










[9] Seth Mnookin, The Panic Virus: The True Story of the Vaccine-Autism Controversy

[10] Seth Mnookin, The Panic Virus: The True Story of the Vaccine-Autism Controversy


[12] Seth Mnookin, The Panic Virus: The True Story of the Vaccine-Autism Controversy


































[46], Accessed May 6, 2021







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