Effectiveness of vaccination against influenza in HIV-infected pediatric patients in the 2016-2017 epidemic season

Abstract

BACKGROUND. Pediatric patients infected with the human immunodeficiency virus (HIV) are at risk of developing severe influenza. Vaccination against influenza in HIV (+) children in Poland is recommended and free of charge. The aim of the study was to evaluate the effectiveness of influenza vaccination in this group of patients. MATERIAL AND METHODS. The study group consisted of 25 HIV-infected children, patients of the Department of Paediatric Infectious Diseases in Wrocław, vaccinated against influenza from September to December 2016. The incidence of influenza and influenza-like diseases was monitored from December 1, 2016 to April 15, 2017. IgG / IgM against influenza A and B by ELISA and against AH1N1 by HI method before vaccination and 4-6 weeks after vaccination were determined. Nasopharyngeal swabs of influenza RNA for PCR testing were collected in each patient during each hospitalization in the epidemic season. RESULTS. In the 2016/2017 epidemic season, none of the patients developed symptomatic influenza or any other flu-like infection with fever. Influenza A virus RNA was detected in nasopharyngeal swabs in 8 patients, none of them presented any clinical symptoms of infection. Positive pre-vaccination IgG levels against influenza A and B were detected in 36% (9/25) and 68% (17/25) of patients, respectively. After vaccination, positive concentrations were found in 56% (14/25) and 80% (20/25) of patients, respectively. Positive concentration of IgM antibodies was achieved by 60% (15/25) of the respondents - for influenza A and 52% (13/25) - for influenza B. In 11 patients (45.8%) before vaccination, protective titres of antibodies against H1 haemagglutinin were obtained, after the vaccination the proportion of patients with a protective titer was 52.4%. CONCLUSIONS. Influenza vaccination in HIV-infected children is effective in preventing symptomatic influenza virus infection but does not prevent transmission of infection in the population. Annual influenza vaccination and seasonal natural infections with influenza viruses result in the persistence of measurable antibody levels until the next epidemic season.