Preplanned Studies: Comparative Analysis of Vaccine Inequity and COVID-19 Transmission Amid the Omicron Variant Among Countries — Six Countries, Asia-Pacific Region, 2022

In this study, six representative countries from the Asia-Pacific region categorized by economic tiers were analyzed to investigate the correlation between immunization and COVID-19 results. The findings suggest that countries with high-income scales exhibit higher rates of complete vaccination, early commencement of vaccination programs, and lower CFR. Additionally, a notable increase in both CFR and MFI was seen in countries with lower vaccination rates in comparison to the country with the highest rate of full vaccination.

The Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) demonstrates greater transmissibility, increased upper respiratory tract prevalence, and lower disease severity compared to previous variants (2). Despite the decrease in disease severity, Omicron’s rapid transmission rates persist as a significant obstacle to pandemic control. The administration of booster doses has been shown to enhance defense against severe COVID-19 during the Omicron surge, with elevated antibody levels sustained for the initial four months post-vaccination (3). Yet, the effectiveness of vaccines appears to diminish over time (4). In summary, while vaccines have significantly curtailed the severity and death rate from COVID-19, they do not offer absolute protection from infection, with cases of “long COVID” prevalent even amidst those who experienced mild or asymptomatic cases of the virus (5). Particularly vulnerable to severe outcomes, including hospitalization and death from COVID-19, are older adults, especially those contending with multiple chronic illnesses, notably cardiovascular or respiratory conditions, or dementia (6).

This study reveals that lower-income countries exhibit lower rates of complete vaccination and later initiation of the vaccination process. This highlights the disparity in vaccine coverage within the Asia-Pacific region and underscores the urgent need for rectification. Our models indicate that by raising the full vaccination rate from less than 70% to more than 90% as accomplished in Indonesia, the MFI decreased by 19.90% and the CFR declined by 8.02%. Consistent with our findings, Watson et al. (7) pointed out that COVID-19 vaccinations have significantly influenced the pandemic’s trajectory. However, limited vaccine accessibility in economically disadvantaged countries has restricted its benefits, reinforcing the urgency for global vaccine equality and comprehensive coverage. The primary global objective should remain focused on amplifying vaccination coverage across the world’s eligible populace, giving special regard to individuals at an elevated risk of severe illness, such as older demographics, cardiac patients, and individuals with dementia (8). This is a significant global concern as stated by COVAX, the World Health Organization’s initiative promoting global equality of COVID-19 vaccine access, which maintains that until all individuals are protected, no one is truly safe (9). Several stratagems to ensure equalized COVID-19 vaccine coverage have been proposed, including expansion of the COVAX facility, waivers for intellectual property rights, amplified manufacturing capabilities within economically disadvantaged nations, reinforced and improved health infrastructure, and implementation of extensive COVID-19 vaccination initiatives (10). In the future, prioritizing and enhancing routine vaccination schedules within high-risk areas of low- and mid-income nations will abet improved control of future pandemics by addressing vaccine scarcity and unequal accessibility.

In the present study, the severity of COVID-19 across six representative countries was evaluated using an array of outcome measures, including mortality, morbidity, CFR, and MFI. An infectious disease’s burden is not solely determined by its case and death counts but also significantly impacted by the total population. Mortality is assessed based on both the number of deaths and the total target population, while CFR factors in the number of cases and deaths. The MFI, a more comprehensive indicator developed for this study, integrates case and death counts with the total targeted population to evaluate COVID-19’s severity. As a general metric, the MFI presents a valuable tool for evaluating and comparing the burden of COVID-19 across various regions. The data analyzed in this study pertain to a period when the Omicron variant represented 100% of COVID-19 cases, thus presenting a picture of the ongoing prevalence of this variant relative to studies featuring earlier variants.

However, some limitations warrant consideration. First, given that reporting of the SARS-CoV-2 variant appears every two weeks, the timing of Omicron’s dominance may be inaccurately represented. Second, the disparity in vaccine types and disease surveillance reporting systems across different countries could potentially bias the results. Third, the beta regression model displayed some underdispersion — an inherent trait of such models — which, while not significantly detracting from our conclusions, invites a more conservative interpretation of hypothesis tests. Furthermore, the existing study lacks data from asymptomatic, mild, moderate, severe, critical, and fatal cases, a spectrum that future research should consider in order to enhance the MFI’s efficiency and accuracy. Despite controlling for potential confounding variables, some factors not accounted for in this research, such as vaccine type, could potentially impact COVID-19 transmission. Thus, caution must be exercised when interpreting the study results.

No conflicts of interest.

The work of the team from Our World in Data. HEAL (Healthy Environments And Lives) National Research Network, National Health and Medical Research Council (Grant No. 2008937), the China Scholarship Council (CSC), and the Centre for Data Science.