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VNA in different age cohorts. The frequency of samples with VNA = 0 drops sharply in age cohorts older than 45 years. For people younger than 45 years old, the proportion of people with VNA ≥ 1/20 titer ranged from 3.2 to 6.7%, and for people older than 45 years old – from 33.3 to 53.2%.
