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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.