Burden of Influenza in Thai Infants: Potential Impact of Maternal Vaccination
Session I – Sanasuttipun, Wiwan
Title of Contribution: Burden of Influenza in Thai Infants: Potential Impact of Maternal Vaccination
Authors: Wiwan Sanasuttipun PhD1, James Mark Simmerman PhD.RN1, Jens Levy PhD1, Jongkol Lertiendumrong, MD.PhD2, Peera Areerat MD3, Denchai Sornkit MD4, Somrak Chantra MD5, Somsak Thamthitiwat MD1, Wichai Sanasuttipun MD6
Affiliation(s):
1International Emerging Infections Program, Thailand Ministry of Public Health -U.S.CDC Collaboration; 2International Health Policy Program, Ministry of Public Health, Thailand; 3Public Health Office, Sa Kaeo Province, Thailand; 4Public Health Office, Nakhon Phanom Province, Thailand; 5Crown Prince Hospital, Sa Kaeo Province, Thailand; 6Nakhon Phanom Hospital, Nakhon Phanom Province, Thailand
Background: Influenza is an important cause of respiratory illness worldwide. Infants are at increased risk for serious complications but influenza vaccine is not approved for infants <6 months. Recent data from Bangladesh suggest that maternal influenza vaccination may be a valuable strategy to reduce disease burden in infants (Zaman et al, 2008). We aimed to describe the incidence of influenza pneumonia requiring hospitalization in Thai children <1 year of age and to explore the potential impact of a maternal vaccination program.
Methodology: We conducted active, population-based surveillance for hospitalized pneumonia in 2 rural Thailand provinces. Clinical pneumonia was defined as evidence of acute infection with signs or symptoms of respiratory disease. A sample of pneumonia patients with chest radiographs within 48 hours of admission provided nasopharyngeal swabs for influenza testing by PCR. We estimated the incidence of influenza pneumonia in children <1 year of age. We then conducted a sensitivity analysis using different cost and vaccine coverage assumptions to estimate the impact of a hypothetical maternal influenza vaccination program with an annual birth cohort of 800,000.
Results: During January 2004-December 2007, we enrolled and tested 1,326 patients less than 1 year of age (60.9% male). Influenza pneumonia was confirmed in 85 (6.4%) infants. The median length of hospital stay was 5.0 days (range 0-18 days). Influenza A was identified in 70 infants (5.3%) and Influenza B in 15 infants (1.1%). Annual influenza pneumonia incidence was estimated to be 139 per 100,000 population. Assuming 80% maternal immunization coverage, 60% vaccine efficacy against laboratory-confirmed influenza in the child, a maternal vaccination program would prevent 534 hospitalizations per year and approximately 2,670 hospital bed days per year.
Conclusions: Thai infants are at increased risk of hospitalization due to influenza pneumonia. Maternal vaccination could provide meaningful public health benefits to both mothers and their infants and deserves consideration in the development of influenza vaccination policy.
