OBJECTIVE: We aimed to compare the clinical, epidemiological, and prognostic features of the H1N1 pandemic in 2009 and the severe acute respiratory syndrome coronavirus 2 pandemic in 2020. METHODS: This retrospective study involved subjects from seven centers that were admitted and found to be positive for H1N1 or COVID-19 real-time polymerase chain reaction test. RESULTS: A total of 143 patients with H1N1 and 309 patients with COVID-19 were involved in the study. H1N1 patients were younger than COVID-19 ones. While 58.7% of H1N1 patients were female, 57.9% of COVID-19 patients were male. Complaints of fever, cough, sputum, sore throat, myalgia, weakness, headache, and shortness of breath in H1N1 patients were statistically higher than in COVID-19 ones. The duration of symptoms until H1N1 patients were admitted to the hospital was shorter than that for COVID-19 patients. Leukopenia was more common in COVID-19 patients. C-reactive protein levels were higher in COVID-19 patients, while lactate dehydrogenase levels were higher in H1N1 ones. The mortality rate was also higher in H1N1 cases. CONCLUSIONS: The severe acute respiratory syndrome coronavirus 2 pandemic is a major public health problem that continues to affect the world with its high rate of contagion. In addition, no vaccines or a specific drug for the benefit of millions of people have been found yet. The H1N1 pandemic is an epidemic that affected the whole world about ten years ago and was prevented by the development of vaccines at a short period. Experience in the H1N1 pandemic may be the guide to prevent the COVID-19 pandemic from a worse end.

Experience with the effect of antiviral therapy on HBsAg seroconversion in acute hepatitis B is limited. We aimed to evaluate the factors affecting HBsAg seroconversion in patients with acute hepatitis B (AHB) receiving antiviral treatment. We performed a retrospective and multicenter study involving 107 adult patients who received antiviral treatment for AHB between January 2018 and December 2023. The median age was 48 (min–max, 18–91) years, and 66.3% of the patients were male; 70 patients with 24-week follow-up (15 patients without HBsAg seroconversion versus 55 patients with HBsAg seroconversion) were compared based on HBsAg seroconversion status. Multivariate logistic regression analysis revealed that age was independently associated with HBsAg seroconversion (odds ratio = 0.926; 95% confidence interval (CI) 0.874 to 0.981; p = 0.009). A one-year increase in age was associated with a 0.926-fold decrease in HBsAg seroconversion. In conclusion, age was an independent predictor of HBsAg seroconversion following acute hepatitis B virus infection.