Effectiveness of A Fourth Dose of COVID-19 mRNA Vaccine in the Elderly Population During the Omicron BA.2 and BA.5 Circulation: A Nationwide Cohort Study in Korea (K-COVE)

Abstract

We estimate the effectiveness of 4th dose booster of COVID-19 mRNA vaccine in individuals aged >=60 years during Omicron BA.2 and BA.5 circulation in Korea. The effectiveness against critical infection was 67.7% (95% CI 50.7%-78.8%) at 31-60 days and 62.1% (45.5%-73.7%) at 61-90 days.

Effectiveness of the second COVID-19 booster against Omicron: a large-scale cohort study in Chile

“…Similar to our findings, the study in Sweden also found moderate waning after 2 months 27 . Likewise, a study in Korea 31 and in Portugal 32 found that a fourth mRNA COVID-19 vaccine dose provided high protection against severe illness compared to a third dose in individuals older than 60 years. Last, anecdotal evidence from two participants in a cohort of healthcare workers in the USA suggests that a second homologous mRNA booster may induce a substantial and durable neutralizing antibody response 37 .…”

“…Policymakers need evidence of realworld effectiveness to guide vaccination policies. However, there is limited evidence for the effectiveness of second boosters, and it primarily refers to mRNA vaccines in Canada, Israel, Korea, Portugal, Sweden, and the USA among populations at higher risk (e.g., older adults and immunocompromised persons) 21,24,25,[27][28][29][30][31][32] . Furthermore, a few studies have examined the potential waning of protection against COVID-19 for second boosters 27 or the effectiveness against severe disease of a second booster dose for individuals who received their primary series based on inactivated vaccines 26 .…”

Willingness to receive the second booster of COVID-19 vaccine among older adults with cancer: a stratified analysis in four provinces of China

“…Notably, this decline is more conspicuous among cancer patients and the older adults relative to their healthier counterparts (12)(13)(14). Contemporary evidence indicates that a second booster dose can enhance the immunogenicity of COVID-19 vaccines in these crucial groups, thereby augmenting vaccine effectiveness and reducing risks of infection, severe illness, hospitalization, and death (15,16). To further substantiate this, the United States Food and Drug Administration (FDA) and China's Bureau of Disease Control and Prevention endorse an additional booster dose for immunocompromised individuals, including the older adults and adults suffering from severe underlying conditions such as cancer, after completing the primary three-dose COVID-19 vaccination regimen (12,17).…”