Impact of varicella vaccination in Argentina: Seroprevalence in children and adults in a pediatric hospital

• Published in: Vaccine: X Vol. 10; p. 100136
• Main Authors: Gentile, Angela, del Valle Juarez, María, Lucion, María Florencia, Pejito, María Natalia, Martínez, Ana Clara, Folino, Agostina, Viegas, Mariana, Giglio, Norberto
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.04.2022; Elsevier
• Subjects: Pediatrics; Regular paper; Seroprevalence; Varicella; Varicella vaccine; Varicella; Pediatrics; Varicella vaccine; Seroprevalence
• ISSN: 2590-1362; 2590-1362
• DOI: 10.1016/j.jvacx.2021.100136

Varicella is the primary infection caused by varicella-zoster virus (VZV). In Argentina, the varicella vaccine was introduced in the National Immunization Programme in 2015 as a single dose scheduled at 15 months of age. To estimate VZV seroprevalence in a healthy hospital based population before and after vaccine introduction to the NIP. Cross-sectional, observational, analytic study. Healthy subjects 1–40 years of age were included between June and December 2019 and tested for VZV-antibodies. Results were compared to data from a similar prevaccination study. Out of 599 samples, 11 indeterminate results were excluded, 424 were positive; overall seroprevalence rate was 72.1% (95 %CI = 68,3–75,8%). No differences were observed between pre and post vaccination studies for overall prevalence or between age groups, except for vaccinated children aged 11–15 (p = 0,005). Rates increased in both periods in subjects aged 6 years or older. Primary vaccine failures were 21%; in subjects <5 years 83% seropositive cases had been vaccinated, in >5 year-olds >90% seropositive cases were associated with a history of infection (OR: 10,4; IC95%: 6,4–16,8; p < 0,001) or household contact (OR:4,8; IC95%: 3,1–7,6; p < 0,001). Vaccination protected against disease (OR: 0.25; 95 %CI: 0.09–0.68; p = 0.004). seroprevalence was high in all age groups except in unvaccinated 12 to 15-month infants. Seropositivity was due to vaccination in 15 months to 5 year-old children and to infection in older children.