Seroprevalence of Protective Antibodies Against Influenza and the Reduction of the Influenza Incidence Rate: An Annual Repeated Cross‐Sectional Study From 2014 to 2019

• Published in: Influenza and other respiratory viruses Vol. 18; no. 5; pp. e13307 - n/a
• Main Authors: Guiomar, Raquel, Pereira da Silva, Susana, Costa, Inês, Conde, Patricia, Cristóvão, Paula, Rodrigues, Ana Paula, Fernandes, Aida, Dias, Ana Paula, Couto, Ana Rita, Ramos, Angélica, Moita, Carina, Rodrigues, Carina, Vale, Fátima, Caldeira, Filomena, Bruges Armas, Jácome, Pereira‐Vaz, João, Alves, José, Freitas, Ludivina, Martins, Luis, Milho, Luís, Mota‐Vieira, Luisa, Lopes, Lurdes, Freitas, Margarida, Pessanha, Maria Ana, Correia, Maria, Marques, Maria Helena, Cardoso, Maria João, Peres, Maria João, Cunha, Mário, Amantegui, Patricia, Mota, Paula, Lopes, Paulo, Pereira, Paulo, Viseu, Regina, Cabral, Rita, Côrte‐Real, Rita, Almeida, Sofia, Soares, Vânia, Mansinho, Kamal, Hungnes, Olav, Nunes, Baltazar
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.05.2024; John Wiley and Sons Inc
• Subjects: Adolescent; Adult; Age; Age groups; Aged; Aged, 80 and over; Antibodies; Antibodies, Viral - blood; Child; Child, Preschool; Children; Childrens health; Correlation coefficient; Correlation coefficients; Cross-Sectional Studies; Disease control; Disease transmission; Evaluation; Female; Females; Health care policy; Health surveillance; Hemagglutination inhibition; Hemagglutination Inhibition Tests; Humans; ILI incidence rate; Immunization; Immunoassay; Incidence; Infant; Infant, Newborn; Influenza; Influenza A Virus, H1N1 Subtype - immunology; Influenza A Virus, H3N2 Subtype - immunology; Influenza B; Influenza B virus - immunology; Influenza Vaccines - administration & dosage; Influenza Vaccines - immunology; Influenza, Human - epidemiology; Influenza, Human - immunology; Influenza, Human - prevention & control; Laboratories; Male; Middle Aged; Original; Population; Population statistics; Population studies; Portugal - epidemiology; Public health; Seasons; Seroepidemiologic Studies; Seroepidemiology; Serology; seroprevalence; Sex; Summer; Vaccines; Viruses; Young Adult; Portugal; Azores; influenza; seroprevalence; antibodies; ILI incidence rate
• ISSN: 1750-2640; 1750-2659
• DOI: 10.1111/irv.13307

ABSTRACT Background Seroepidemiological studies provide estimates of population‐level immunity, prevalence/incidence of infections, and evaluation of vaccination programs. We assessed the seroprevalence of protective antibodies against influenza and evaluated the correlation of seroprevalence with the cumulative annual influenza incidence rate. Methods We conducted an annual repeated cross‐sectional seroepidemiological survey, during June–August, from 2014 to 2019, in Portugal. A total of 4326 sera from all age groups, sex, and regions was tested by hemagglutination inhibition assay. Seroprevalence and geometric mean titers (GMT) of protective antibodies against influenza were assessed by age group, sex, and vaccine status (65+ years old). The association between summer annual seroprevalence and the difference of influenza incidence rates between one season and the previous one was measured by Pearson correlation coefficient (r). Results Significant differences in seroprevalence of protective antibodies against influenza were observed in the population. Higher seroprevalence and GMT for A(H1N1)pdm09 and A(H3N2) were observed in children (5–14); influenza B seroprevalence in adults 65+ was 1.6–4.4 times than in children (0–4). Vaccinated participants (65+) showed significant higher seroprevalence/GMT for influenza. A strong negative and significant correlation was found between seroprevalence and ILI incidence rate for A(H1N1)pdm09 in children between 5 and 14 (r = −0.84; 95% CI, −0.98 to −0.07); a weak negative correlation was observed for A(H3N2) and B/Yamagata (r ≤ −0.1). Conclusions The study provides new insight into the anti‐influenza antibodies seroprevalence measured in summer on the ILI incidence rate in the next season and the need for adjusted preventive health care measures to prevent influenza infection and transmission.