The medical care of older adults often involves the management of chronic illnesses. Typically, therapeutic interventions for chronic illnesses consist of prescribed medication. As health problems tend to accumulate with age, older adults often have multiple comorbidities and are required to consume a variety of medication. Polypharmacy—the concomitant use of multiple drugs by a single individual—is an issue in present models of healthcare (44–46). The ubiquitous use of prescribed drugs in older adults health management may hence frame these older adults' understanding of viruses like the COVID-19, thinking that they may be treated through medications readily prescribed by doctors (47). Consequently, older adults with this misconception may not view vaccination as necessary. This notion aligns with schema theory, which posits that when new information becomes available (i.e., COVID-19 vaccination), a person tries to fit this new information into the pattern which he/she had used in the past to interpret information regarding a similar situation (48). Similarly, as the healthcare regimen of older adults often involve the reduction and management of existing conditions, the preventive role vaccinations play may not be readily understood. Some older adults may see the COVID-19 vaccine as means to cure or manage disease symptoms, needed only by individuals who have contracted the virus (47, 49). Continuing on this notion of cognitive framing, regular prescription of a healthy lifestyle to combat chronic illness may also lead some to think that they may turn to these as alternatives to the vaccine (50, 51). They may form a misbelief that robust immunity from the COVID-19 virus may be achieved through exercising, eating healthy, taking vitamins, or avoiding sick people (49, 52).

Vaccination side effects such as fever, chills, fatigue and swelling of lymph nodes are typical. The introduction of a foreign substance into the body elicits an immune response, and while certain individuals may not exhibit these side effects, its presence in mild forms does not warrant immediate concern. Immune response following vaccination is important, generating the appropriate antibodies to fight off future infections. While unpleasant, some older adults may view potential COVID-19 vaccine symptoms disproportionately negative (53). Some may misconstrue these side effects as “sickness,” and mislabel the COVID-19 vaccine as disease-causing (49, 54). Even when these side-effectives are appreciated as normative biological responses, some older adults may feel that their general frailty and/or ailments exclude them from vaccine suitability (47). Given the coverage on COVID-19 vaccine side effects such as blood clotting disorders from the Oxford AstraZeneca vaccine (55) and myocarditis associations with the Pfizer-BioNTech and Mordena vaccines (56, 57), this may perpetuate the misnomer that only fit individuals are suited for COVID-19 vaccines. Some older adults may also have the misconception that the COVID-19 vaccine is primarily for people travelling overseas and those who frequent crowded settings (47, 49), a misconception possibly derived from extensive media coverage on restricted air travel and safe distancing measures. While greater contact with others and travel does increase the likelihood of infection, infections do occur domestically and within small groups.

Perceived disease susceptibility and severity of health threat form two important tenets of health behaviour engagement. According to the Protection Motivation Theory (58), these two components underpin overall threat appraisal. Working in tandem with perceived coping efficacy, they result in either adaptive (e.g., adopting health behaviour) or maladaptive responses (i.e., denial of health threat).

Perceived susceptibility reflects the appraisal of subjective risk to a negative situation (59, 60), such as an infection. Motivation to forgo pleasurable behaviours and engage in inconvenient protective health behaviour is in part driven by greater perceptions of infection susceptibility (61–65). Over the course of the pandemic, countries have developed and implemented various measures aimed at containing COVID-19 infection cases. In countries where the infection curve has been flattened or have lower incidences, perception of infection susceptibility may be reduced, and these populations may not feel the pressure to be vaccinated (21, 54). Previous research on the influenza vaccine have also found past episodes of influenza infection tended to substantiate notions of disease susceptibility (47). A lack of past COVID-19 infections and low incidence of community infections may lead some to trivialise the probability of COVID-19 infection, and hence may not be willing to be vaccinated.

Perceived health threat severity may be evaluated through group comparisons. When considering one's vulnerability to a particular disease, a stereotypical image of a high-risk group emerges (66, 67). Following which, a process of social comparison occurs, assessing similarities and differences between this stereotypical group and oneself (68). Inaccurate inferences impaired by self-enhancement biases may shape perceived vulnerability towards infection. For example, older adults who did not identify as being old or frail were less likely to abide by government guidelines to protect against overheating, trivialising potentially severe health implications; this was despite them being considered at risk objectively (69). Similarly, older adults who did not identify as sickly and frail were found were found to refuse vaccination on grounds that they had generally been healthy (49, 54), despite being considered at risk objectively (28, 29).

Consequently, behaviour engagement are held to be more likely when an individual perceives oneself to be faced with a health threat to which he/she is susceptible and which is perceived to be severe (41, 58).

COVID-19 fatigue has certainly been experienced by many, yet, vigilance and tenacity is still needful. Given the sizable population of older adults and their vulnerability to the disease, having a large percentage of these older adults vaccinated is fundamental. Recent research suggest that the willingness to vaccinate against COVID-19 might be systematically underestimated, and introducing certain virus-related information (i.e., information about herd immunity) significant increases vaccination willingness (70). This highlights the modulating capability of nuanced messaging on vaccination willingness. Identifying subpopulations and demographic descriptors of unvaccinated seniors are important, however, it is equally important to understand the misconceptions, concerns and fears specific to this group of elderly individuals. When addressing the aforementioned barriers, it is also necessary to consider appropriate and accessible channels. Previous research has suggested that targeted messaging and intervention may be more effective when introduced through a family doctor (54), grassroots volunteers from the community using a multi-component approach [i.e., home visits, telephone and leaflets reminders; (71, 72)], and through traditional media such as television and newspapers (73). Further, as older adults may be more susceptible to misinformation (74, 75), establishing that messages through said channels are verified—whether through government (76) or journalist intervention (77)—and education on digital literacy (78, 79) may serve as potential counters.

The first draft of the manuscript was prepared by JC. Both authors contributed to manuscript revision, read, and approved the submitted version.

This research was supported by a grant awarded to AH by Singapore Management University through research grants from the Ministry of Education Academy Research Fund Tier 1 (20-C242-SMU-001) and Lee Kong Chian Fund for Research Excellence.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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