Analysis on antibody levels to seasonal influenza viruses in healthy adults in Beijing, 2017

ObjectiveTo investigate the immune level against seasonal influenza viruses in healthy adults in Beijing.

MethodsIn April 2017, the study subjects were randomly selected from communities in six districts in Beijing. A questionnaire survey was conducted among them and serum samples were collected from them to detect the antibodies against seasonal influenza viruses, including influenza A (H1N1) pdm09 virus, influenza A (H3N2) virus, influenza B virus Victoria lineage and influenza B virus Yamagata lineage. The positive rates of the antibodies and the genmetric mean titers (GMTs) in different groups were compared.

ResultsA total of 1 163 healthy adults were surveyed, in which 645 were positive for at least one antibody. The positive rates for A (H1N1) pdm09, A (H3N2), B Victoria lineage and B Yamagata lineage viruses were 25.62%, 44.88%, 1.98% and 3.53% respectively. The antibody against A (H3N2) virus had the highest GMT of 1∶24.75, while the GMT of antibody against B Victoria lineage virus was lowest (1∶5.67). The differences in antibody positive rate and GMT were significant among the four subtype influenza viruses (P＜0.001). The positive rates of antibodies against A (H3N2), B Victoria lineage and B Yamagata lineage viruses and the GMT of A (H3N2) virus antibody were higher in males than in females (P＜0.05). There were significant differences in positive rates of antibodies against A (H1N1) pdm09 virus and A (H3N2) virus and the GMTs among the populations from different districts (P＜0.05). Similar results were observed in different age groups for the positive rates of antibodies against A (H1N1) pdm09, A (H3N2) and B Yamagata lineage viruses (P＜0.001). The antibody level to A (H3N2) virus and GMT were highest in age group ≥60 years , while the antibody levels to A (H1N1) pdm09 virus and B Yamagata lineage virus and GMTs were highest in age group 18–29 years. The persons receiving vaccination in past year had higher positive rates of antibodies and GMTs against A (H1N1) pdm09, A (H3N2) and B Yamagata lineage viruses compared with unvaccinated persons (P＜0.05).

ConclusionThe positive rates of antibodies against B Victoria lineage and B Yamagata lineage viruses were low in healthy adults in Beijing, suggesting the high risks for outbreaks of infections of B Victoria lineage and B Yamagata lineage viruses. The factors influencing the antibody levels of different subtype influenza viruses slightly differed, and there was a correlation between vaccination or other factors and antibody positive rate.