IMPACT OF ROUTINE VARICELLA IMMUNIZATION ON VARICELLA INFECTION AND HERPES ZOSTER INCIDENCE RATES AMONG CHILDREN AND ADOLESCENTS IN GREECE

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E. Critselis, E. Klinaki, I. Koutsoubari, M. Mavrikou, O. Dedousi, M. Tsolia, V. Papaevangelou,

National and Kapodistrian University of Athens School of Medicine Second University Department of Pediatrics, 'P. & A. Kyriakou' Children's Hospital, “P. & A. Kyriakou” Children’s Hospital First Department of Pediatrics, 'P. & A. Kyriakou' Children’s Hospital Second Department of Pediatrics, NHS,

Aim: To study the impact of varicella vaccination on ambulatory visits due to varicella and HZ at the “A & P Kyriakou” children’s hospital.

Methods : Study protocol was approved by the hospital Ethics Review Board. A review of the emergency attendance records of the Pediatric Department from January 1, 1998, through December 31, 2010, was conducted.

Statistical analysis: The incidence rates were calculated based on the total number of emergency department attendances during the study periods:

(1)Prelicensure period (1998-2003): 321,506 children (53,584/yr) (2)Postlicensure period (2007-2010): 185,059 children (46,265/yr). The prelicensure period was applied as the basis of comparison for analyses. The interim period (2004-2006) was not included since vaccine coverage was low. P values<0.05 were considered the criterion of significance. Statistical analyses were performed using SAS version 9.1 and Rao-Scott Chi-Square test.

Results:

The progressive expansion of vaccine coverage over the years was followed by a corresponding decrease in VZV cases. The incidence rate of varicella infection was significantly reduced during the postlicensure period (p<0.0001). The observed trend was markedly notable among both younger and older children. However, the decrease was noteworthy solely among Greek infants and children. (Table 1). Similarly, a significant decrease in the occurrence of herpes zoster cases was observed during the postlicensure period among children aged greater than 5 years and of Greek origin. (Table 2)

Conclusions:

Wide implementation of varicella vaccine has lead to a noteworthy decrease in ambulatory visits due to both varicella and HZ in our tertiary hospital. To date, no increase in the mean age of varicella cases has been observed. A concern is raised since virus still prevails, mostly among underserved minority groups indicating low vaccine coverage in these groups. Continuing surveillance of both diseases is necessary. Catch up vaccination of susceptible adolescents should be a priority in our area, where seropositive rates in adolescents are lower than those observed in N. Europe.