Studies show that seasonal influ enza in Northeastern state of – Ceará occurs 2-3 months earlier than in the South and Southeast, where the national calendar of vaccination is based. The study will test if Brazil’s national policy targeting vaccination only in April and May inadequately protects against the harmful maternal-fetal effects of influenza in the Semi-Arid and northern regions.
The linkage of the complete tables from SINASC and SINAN available for this study was performed. Individuals with fever, referred, monitored for cough or sore throat, and with symptom onset within the last 7 days (influenza-like syndrome) were selected using the Influenza Notifiable Diseases Information System (SINAN-Influenza), Ministry of Health, Health Surveillance Secretariat. For information on the influenza vaccination program over the past five years, data from the National Immunization Program (PNI, DATASUS; pni.datasus.gov.br) were used.
Recent models indicate that the semi-arid region of Ceará, home to a population of 8.8 million, serves as the starting point for seasonal influenza transmission in Brazil. Studies suggest that the peak of influenza activity occurs before immunization campaigns begin. This study confirmed errors in the immunization schedule in Ceará and identified a significant burden of influenza among pregnant women and young infants.
From 2013 to 2018, morbidity attributable to severe acute respiratory disease (SARD) and influenza was assessed based on age, pregnancy status, and influenza subtype. Using data from the Live Birth Information System (SINASC) from the Ministry of Health, outcomes for children born to women with and without SARD were compared, and seasonal fluctuations in birth weight and pregnancy were analyzed.
In total, 3,297 cases of SARD were identified, of which 145 (4%) occurred in pregnant women. The peak incidence of SARD and influenza coincided during epidemiological weeks 15 to 20. Notably, immunization campaigns were conducted during or shortly after the peak influenza activity.
Cyclical fluctuations in birth weight and gestational age were observed, aligning with sharp declines during epidemiological weeks 50 to 10. Sixty-one infants born to mothers who had SARD during pregnancy were identified. These 61 infants had an average birth weight that was 10% lower (2,879 ± 784 g compared to 3,196 ± 573 g; P = 0.019) than those born to mothers without SARD (n = 122) and had a higher likelihood of premature birth (relative risk 3.15; 95% confidence interval: 1.52 to 6.52).
These findings suggest that influenza negatively affects pregnancy and birth outcomes in Ceará. Implementing vaccination campaigns before the peak of influenza activity could significantly improve outcomes in the state and may yield benefits for regional and national transmission dynamics.
Influenza in Ceará, located in Brazil’s semi-arid region, peaks 2 to 3 months earlier than in the Southern and Southeastern regions of the country. Interestingly, the influenza strains identified in Fortaleza are more closely related to those circulating in the Northern Hemisphere. Despite these documented epidemiological differences, Brazil follows a uniform vaccination schedule nationwide. This approach leads to inadequate protection for pregnant women and their fetuses against influenza in tropical and equatorial regions. The seasonal patterns of influenza A/H1N1 and A/H3 viruses in this area underscore the need to reconsider national strategies for influenza immunization campaigns. Reevaluating these strategies is crucial to preventing the intergenerational transmission of disease burden.
These findings indicate that influenza adversely impacts pregnancy and birth outcomes in Ceará. Implementing vaccination campaigns prior to the peak of influenza activity could significantly enhance outcomes in the state, likely benefiting transmission dynamics at both regional and national levels.