Optimism bias, vaccine hesitancy and the ‘underlying condition’ nobody is talking about

6 min

Throughout the COVID-19 pandemic, we have grown accustomed to continual reports of deaths among the elderly and people with “underlying conditions”. These messages cause feelings of isolation and devaluation of the lives of people who share these risk factors for severe illness and death from COVID-19 and likely lulled many of the rest of us into a false sense of security.


Optimism bias influences beliefs and behaviours towards COVID-19

Most of us have an optimism bias that leads to an attitude of “it won’t happen to me” when it comes to adversity. We believe bad things are less likely to happen to ourselves than other people, and good things are more likely to come our way. Optimism bias fosters perseverance in the pursuit of goals and encourages effort towards overcoming obstacles. However, discounting the likelihood of unwanted events can lead us to engage in potentially dangerous activities or avoid taking necessary caution.

Optimism bias explains why more than 15% of Australians are more concerned about the effects of COVID-19 on the health of others than they are for themselves, due to self-underassessment of their own vulnerability to the disease.

The trouble with optimism bias is that our unrealistically positive expectations are resistant to change, especially in response to negative information. For example, a person who estimates their risk of COVID-19 to be 20% but is then informed that the real risk is 30%, doesn’t revise their estimate up as much as if they would revise it down if the real risk was 10%.

Australians’ fear of COVID-19 during the early stages of the pandemic dissipated as our geographic isolation, social distancing and lockdowns reduced our risk of the disease. As “doughnut days” repeated, we began to believe that COVID-19 was not as bad for us as it was for others.

Now, the Delta variant of the virus – with its increased transmissibility and potential to cause more severe disease than the original form of the virus – has exposed these beliefs as unrealistically optimistic.


Male vulnerability

Males may have a greater optimism bias than females, which could be why men are more likely than women to take risks and have correspondingly high rates of diseases resulting from such behaviour. It might also contribute to men’s delay (when compared to women) in seeking help for health problems, thereby contributing to their shorter life expectancies and their greater share of the national burden of disease.

In Australia, death rates from COVID-19 in males are one-third higher than those of females, regardless of age. International data show that males are more likely than females to be hospitalised, require intensive care, or die because of SARS-CoV-2 infection.

The risk of death from COVID-19 is 59% higher for males than females. This increase in risk is greater than that caused by many of the pre-existing conditions that we have come to accept as associated with COVID-19 deaths: including Class I and II obesity (5% and 40% increased risk of death compared to healthy body weight), being a former smoker (19% increased risk compared to never smoking), asthma needing inhaled corticosteroids (13% increase compared to non-asthmatics), heart disease (17% increase), controlled diabetes (31%) and some people with a previous cancer diagnosis or autoimmune disease.

Males hospitalised with COVID-19 are 45.7% more likely to die than females. The magnitude of the risk of death in hospitalised males is higher than the risk of death for hospitalised COVID-19 patients with: peripheral vascular disease (23% higher than those without), a history of heart attack (7% higher risk), cerebrovascular disease (18% higher), chronic lung disease (9%), rheumatic or other connective tissue disease (24%), peptic ulcer (6%), mild liver disease (2%), diabetes with long term complications (30%) or without (16%), paraplegia and hemiplegia (15%), and kidney disease (16% increased risk).

These are not the only studies to demonstrate that “after adjusting for demographics and comorbidities, male sex was an independent risk factor for mortality, intubation, and intensive care”.


When COVID-19 vaccines first became available the risk of potential serious adverse effects of vaccination was greater than the health risks of COVID-19 for some people. The situation now is different though.

The blood clotting problems that prompted caution about the Astra Zeneca vaccine have proven to be much rarer (affecting 1 in 30,000 to 50,000 Australians who receive the vaccine) than the prevalence of blood clots associated with COVID-19 (up to 1 in 2 with severe disease and 1 in 500 for people with COVID-19 who do not need hospitalisation). Given the number of COVID cases in Australia over the next few months will reach at least 10% of the population, the odds are now at least 10 to 1 in favour of the vaccine.

Unvaccinated people are five times more likely to be infected and 29 times more likely to be hospitalised with COVID-19, and among hospitalised COVID-19 patients, the unvaccinated are three times more likely to die.

Because of our optimism bias, the evidence that we should be more concerned about our risk from COVID-19 and less worried about side effects of vaccination is not enough for us to make accurate predictions about our personal risk. We can see evidence of this in Australians’ attitudes to getting vaccinated against COVID-19. Vaccine hesitancy rates are high in Australians aged under 45, and those in Queensland, South Australia and Western Australia.

A gendered approach to health

Since the beginning of the availability of COVID-19 vaccinations in Australia, vaccine hesitancy has averaged 25.7% for males and 32.3% for females but there are around 500,000 fewer Australian males who have received a first dose of vaccine.

The barriers that prevent males from accessing healthcare services more generally are likely to be responsible for relatively lower COVID-19 vaccination rates in Australian males. Removing these barriers and enacting practices that facilitate males’ access to healthcare are desperately needed, not just to make up the gender disparity between rates of COVID-19 vaccination, but to achieve equity overall in health between males and females.

COVID-19 provides a stark example of why gendered medicine, which accounts for differences in biology, psychology and sociology between males and females is required. Health system inequity doesn’t just impact males. If hospitals fill up with male COVID-19 patients, healthcare for people of all genders will suffer.

We also need an effective gendered approach to data reporting and medical research. Even though there is general agreement within the research community that sex and gender should be considered when studying biology and developing and trialling new therapies, research practice is deficient. In the midst of a pandemic with a clear gender bias, only 17.8% of published clinical trials of COVID-19 treatments report gender-specific results or analyses. An even smaller proportion of registered clinical trials that are planned or underway looks to deal adequately with gender.

Hopefully, the pre-existing condition of being male will not continue to be disregarded by researchers, health systems and policymakers. Everyone’s lives depend on it.


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