Introduction

From January to August 2020 in Mexico, Covid-19 was the second cause of death in men and the third cause in women according to official reports.¹ Vaccination against SARS-CoV-2 is a major primary intervention to prevent Covid-19. It has been estimated that 75 to 90% of the population needs to be vaccinated to achieve herd immunity.² To do so, we need effective, affordable, and accessible vaccines. However, the success of Covid-19 vaccination programs also depends on the populations willingness to accept the vaccine. It has been reported that women,^3,4,5,6 people without employment,^4,5,6 and in lower socioeconomic levels6 tend to refuse or hesitate more frequently Covid-19 vaccination. Describing the associated factors with vaccination refusal considering the context of each country is key to understand countries differences and target interventions.

Misinformation about vaccine efficacy and safety could decrease acceptance for Covid-19 vaccines. Anti-vaccination groups have become prominent around the world and are actively calling for the refusal to vaccinate against Covid-19.⁷ Mistrust about vaccine benefits, concerns about potential side effects^8,9 as well as over the speed of vaccine development have been associated with uncertainty and unwillingness to vaccinate against Covid-19.⁶

Of particular concern is the possibility of higher refusal and hesitancy among groups at higher risk for Covid-19 complications and mortality, such as men and people over 50 years of age.¹⁰ Comparing the acceptance of the Covid-19 vaccine versus influenza’s could help to identify if a refusal to all vaccines is occurring in Mexico. Also, analyzing specific subgroups with higher vaccine refusal and hesitancy will help to identify target subgroups for information campaigns and to prepare an appropriate and equitable vaccination campaign.

We aimed to estimate the willingness to vaccinate against Covid-19 and to identify socioeconomic factors associated with vaccine refusal and hesitancy, using a nationally representative sample of the Mexican population. We also identified the key groups with low vaccine acceptance but high mortality risk due Covid-19.

Materials and methods

Results

Overall, 62.3% of the population accepted the Covid-19 vaccine, 28.2% refused and 9.5% hesitated. The highest acceptance was observed among 20-29 years old (68.3%), and the lowest among participants 60 years and older (54.0%). Hesitancy also increased with age, from 6.7% in adults 20 to 29 years to 11.7% among participants 60 years and older. Females, in comparison to males, showed lower acceptance, and higher refusal and hesitancy to the Covid-19 vaccine. Acceptance increased with higher education and socioeconomic status. By employment status, formal employees showed the highest acceptance. We observed heterogeneity in acceptance across regions, with Mexico City presenting the highest acceptance (69.3%) and Central Pacific the lowest (54.7%). Those who reported Covid-19 symptoms had the highest acceptance rate (72.3%); pauci-symptomatics had the highest hesitancy (12.9%), and asymptomatic the highest refusal (29.6%) (table I).

Table II presents the socio-demographic factors associated with refusal and hesitancy among adolescents and adults. Age was associated with a higher relative probability of refusal over acceptance, being 1.24 for participants 30-39 years, 1.21 for 40-49 years, and 1.43 for 60 and older. Similarly, the relative probability of hesitancy over acceptance was 1.4 for participants 50-59 years, and 1.55 for adults 60 years of age and older, in comparison to the 16-29 years group. Females, compared to males, had 1.15 times the relative probability of refusal over acceptance and 1.37 times the relative probability of hesitancy over acceptance. Compared to formal employees, unemployed and informal employees had 1.53 and 1.71 times the relative probability of refusal over acceptance to vaccination. In addition, informal employees had 1.58 times the relative probability of hesitancy over acceptance, compared to formal employees. Compared to Mexico City, the Central-North region had 1.6 times the relative probability of refusal over acceptance to vaccination, while Central-Pacific, Central-North, Center, North-Pacific and South-Pacific had higher relative probability of hesitancy over acceptance (2.1 times, 2.32 times, 1.93 times, 1.87 times and 1.62 times, respectively). Also, being asymptomatic, lower education and socioeconomic status were associated with higher refusal over acceptance.

Table III shows the ratio of mortality to acceptance for Covid-19 vaccines. Acceptance was always higher than Covid-19 mortality risk (ratio below 1). A perfect scenario is a ratio near zero because either the acceptance is considerably higher than mortality or mortality is very low. Men aged 60 years and older showed values higher than 0.5 in all regions, while women aged 60 or older presented ratios ranging from 0.34 to 0.69. Among participants 60 years and older, the highest ratio of mortality/acceptance-the mortality risk is similar vaccine acceptance-was observed in males living in the in North-Pacific (0.94), followed by males living in the in South-Pacific (0.77), males living in the Central-Pacific (0.72), males living in the North-Border (0.71), males living in the State of Mexico (0.70) and females living in the North-Pacific (0.69).

Discussion

From August to November 2020 in Mexico, the acceptance for Covid-19 vaccination was 62.3%, refusal 28.2% and hesitancy 9.5%. We found that older adults, females, and workers in the informal sector reported higher refusal and hesitancy. In contrast, higher education and higher socioeconomic status were associated with lower refusal and hesitancy. Refusal and hesitancy were higher in groups at a higher risk of Covid-19 mortality, in particular people over 60 years of age.

The acceptance rate of the Covid-19 vaccine in this study (62%) was lower compared to the average acceptance rate in Mexico reported in a global survey conducted in 19 countries in June 2020 (76.2%) and lower than the global average (71.5%).¹⁴ However, as the global survey was not nationally representative, we cannot rule out the possibility of selection bias. Another nationally representative survey among Mexican adults conducted in November 2020 reported an acceptance of 82%; however, this figure included both answers, “definitely will get vaccinated” and “unsure, but probably will get vaccinated”, which in our case were considered hesitant.¹⁵ It is important to consider the different time frames of the surveys. It has been documented that the acceptance of Covid-19 vaccine can change over time.¹⁶ Since the information regarding the vaccines’ effectiveness and safety changes over time, the differences in results across surveys could be explained by collection dates.

The prevalence of Covid-19 vaccine refusal increased with age, and individuals aged 60 years and older had the highest odds of refusal and hesitancy. This is different to other countries where the elders are more likely to accept the Covid-19 vaccines.^14,16,17 This finding is particularly worrisome, considering the burden of morbidity and mortality experienced by older adults, particularly men, in Mexico.¹ A previous study reported that the main determinant for refusal in the elderly is the perception of Covid-19 severity,¹⁸ which suggests that Mexican elders could be having a lower perception of disease severity, although the true underlying cause cannot be explored with our data. We also observed a higher refusal and hesitancy in women compared to men, a finding that was previously reported and explained as potentially linked to a difference in the perceived safety of the vaccines.³

We observed that Covid-19 vaccine acceptance was higher than the mortality risk in all age groups, indicated by a low mortality: acceptance ratio. However, we also noted that the groups at higher risk of Covid-19 mortality-those 60 years and older-showed the highest ratios in all regions. If individuals at higher risk of complications refuse or hesitate to get vaccinated, Covid-19 fatalities in Mexico will continue to rise as new waves of infection happen. Unfortunately, the information available in Ensanut 2020 Covid-19 was limited and did not include reasons for refusal and hesitancy. Future studies will be needed to further identify the reasons behind vaccination hesitancy and refusal.

While the Ensanut 2020 Covid-19 survey did not explore the reasons for refusal and hesitancy, we made the comparison with the stance towards influenza vaccine to explore if it was a general refusal towards vaccines. Influenza vaccines are well known by the population, as national campaigns for influenza vaccination are organized every year since 2014.¹⁹ When compared to the influenza vaccine, the acceptance of Covid-19 vaccination was lower (62.3 vs. 68.1% in influenza) and hesitancy was higher (9.5% compared to 3.5% in influenza). Particularly participants 60 years and older reported a higher acceptance for influenza (69%) than Covid-19 (53.9) (figure 1). This result suggests that specific aspects of the Covid-19 vaccines could explain the low vaccination acceptance and does not reflect a general refusal stance towards all vaccines. This is positive, as targeted information and communication could increase acceptance towards Covid-19 vaccines.⁹ Beliefs and perceptions about the Covid-19 vaccines should be addressed in the groups at higher risk of refusal and hesitancy, as identified by Ensanut 2020 Covid-19, providing clear messages about efficacy, safety, and benefits of Covid-19 vaccines which have been reported as determinants for refusal or hesitancy.⁶

Figure 1 Comparison of acceptance, refusal and hesitancy to Covid-19 and influenza vaccines by age group. México Source: Ensanut 2020 Covid-19, 2020 

Unemployed and informal employees had higher refusal (32.0 and 32.1%, respectively) and hesitancy (11.1 and 10.7%) compared to formal employees (19.3% refusal and 7.4% hesitancy). A low vaccine uptake in this group could further increase health inequalities and perpetuate them. In Mexico, 60% of workers participate in the informal sector,²⁰ meaning a lower opportunity to do home-office and a higher exposure to SARS-CoV-2 coupled without social and health security. Thus, beyond defining a targeted information campaigns, it will be necessary to identify key strategies to facilitate vaccination for informal workers, ensuring easy access to the vaccines.

Readers should be aware of the limitations of our study. The two most critical limitations stem from the cross-sectional nature of the study. First, Covid-19 vaccine acceptance is dynamic, as reported in other countries.¹⁶ The willingness to accept the vaccine is influenced by factors that might change over time, particularly in the case of Covid-19, a novel virus known only a few months before the survey. However, previous studies have shown that willingness to accept a vaccine is a good predictor of actual vaccination behavior²¹ and is useful information until new one becomes available. Second, the question in the survey was about a generic, hypothetical vaccine. By early 2021, five different vaccines have been approved in Mexico.²² Acceptance can be different by vaccine.

Developing a safe and effective vaccine is just a step in the immunization process. In addition to the challenges related to vaccine access and distribution, the population’s willingness to be vaccinated is crucial. In Mexico, 38% of the population refuses or hesitates to receive a Covid-19 vaccine, particularly among vulnerable groups: older people, unemployed and informal workers. The refusal and hesitancy of Covid-19 vaccine could jeopardize herd immunity and delay the population benefits of the vaccine, such as a reduction in the number of hospitalizations and deaths. It could also create pockets of unvaccinated individuals amongst the most vulnerable populations, that will carry the burden of potential disease outbreaks. Our study contributes to identify vulnerable groups to further explore the specific barriers by qualitative or mixed-method research and create evidence-based campaigns and well-targeted interventions to facilitate acceptance could yield important public health and social benefits.