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Feng et al in their randomized control trial of vaccine efficacy study determined a binding antibody unit of 264 or a pseudo-virus neutralization assay titer of 26 IU/ml corresponded to 80% efficacy against symptomatic COVID-19 though they could not determine threshold for asymptomatic infections in their study.32Therefore, more studies with a long-term follow-up on larger population (including vulnerable and different spectrum of immunocompromised individuals) are required to define the reliable vaccine specific correlates of protection as in Hepatitis B.
In summary, the study found that both healthy individuals and cirrhosis patients generate similar levels of memory T-cells after being vaccinated, which is an indication of effective and durable immunity. Therefore, cirrhosis patients may not need additional vaccine doses compared to healthy individuals.
One of the strengths of the study is that it examined the detailed cellular and humoral immune responses of cirrhotic patients with varying degrees of liver disease severity and causes, over a one-year period after receiving the ChAdOx1nCoV-19 vaccine. However, a limitation of the study is the small sample size, with fewer patients in the CTP class C category.