Background: Invasive disease due to Haemophilus influenzae b (Hib ID) was a major cause of mortality and sequelae among children in Argentina before the introduction of a highly-effective vaccine in 1998 through a scheme of 3 doses (2, 4, 6 months) and a booster (15-18 months). In recent years, however, an increase in the disease incidence was observed as well as in other countries of the region. Objective: To describe the epidemiological profile, the incidence of invasive disease due to Hib in Argentina and Hib vaccination coverage. To estimate the effectiveness of Hib vaccination among children <1 year.
Methods: Descriptive ecological study. Cases of invasive Hib ID reported to the National Ministry of Health between 2013-2015 were included. The characteristics and vaccination status of cases of Hib ID were analyzed. Vaccination effectiveness (VE) in children <1 year was estimated using Orenstein method: VE=(%VP - %VC) /%VP (1 - %VC). VP: vaccinated population; VC: vaccinated cases.
Results: Between 2013 and 2015, 274 cases of Hib ID were recorded. Figure1.
The average coverage for the 3rd dose and the booster dose was estimated in 91.6% (86.8 to 94.1%) and 79.1% (73.5 to 80.2%), respectively (preliminary data).
The median age of cases was 8 months (IQ:5-13), of which 67% were aged <12 mo and 90.4% were aged <24 mo; 54% were male. Nineteen, out of 24 provinces notified cases, without a seasonal pattern. Most frequent clinical presentations were meningitis (55.5%), pneumonia (17.1%) and bacteremia (8.8%). No differences were observed in the 3-year period.
Proof of vaccination was available for 71% (196) of cases; 39.3% had a complete primary series, 51% <3 doses and 9.7% received no vaccine doses. The median age of vaccination was as follows: 1st dose 2.5 mo (1.8-13.5), 2nd dose 4.5 mo (3.9-6.7), 3rd dose 6.7 mo (6-21), booster dose 18.4 mo (13.1-33). Figure 2
Conclusion: The increase of Hib ID incidence in Argentina could be multi-factorial and attributable to non-uniform vaccination coverage, delayed schedules and a non-satisfactory coverage for the booster dose that could lead to insufficient herd immunity.
M. D. V. Juarez,
S. Neyro, None
C. Biscayart, None
N. Katz, None
M. Pasinovich, None
M. Lopez Yunes, None
A. Aquino, None
C. Vizzotti, None