Impact of Rotavirus Vaccine Introduction and Vaccine Effectiveness in the Republic of Moldova

Abstract

Background: The Republic of Moldova was the first low- to middle-income country in the World Health Organization European Region to introduce rotavirus vaccine (July 2012). We aimed to assess the impact of the rotavirus vaccine program and estimate vaccine effectiveness (VE).

Methods: Surveillance for rotavirus gastroenteritis was conducted in 2 hospitals in the capital city of Chisinau starting in September 2009. Monthly rotavirus admissions by age were examined before and after introduction of rotavirus vaccination using interrupted time-series analyses. We performed a case-control study of VE by comparing rotavirus case patients with test-negative controls.

Results: Coverage with at least 1 dose of vaccine increased from 35% in year 1 to 55% in year 2 for children <1 year of age. The percentage of hospital admissions positive for rotavirus fell from 45% in the prevaccine period to 25% (rate reduction, 36%; 95% confidence interval [CI], 26%-44%) and 14% (rate reduction, 67%; 95% CI, 48%-88%) in the first and second years after vaccine introduction, respectively, among children aged <5 years. Reductions were most pronounced among those aged <1 year. Significant reductions among cohorts too old to be vaccinated suggest indirect benefits. Two-dose VE was 79% (95% CI, 62%-88%) against rotavirus hospitalization and 84% (95% CI, 64%-93%) against moderate to severe rotavirus.

Conclusions: These results consistently point to profound direct and herd immunity impacts of the rotavirus vaccine program in young children in the Republic of Moldova. Vaccine coverage was modest in these early years following introduction, so there remains potential for further disease reductions.

Keywords: Moldova; case-control; rotavirus; surveillance; vaccine effectiveness.

Figure 1.

Age in weeks of receipt of dose 1 (A) and dose 2 (B) of monovalent rotavirus vaccine, Moldova, August 2012–July 2014.

Figure 2.

A, Rotavirus–positive and rotavirus-negative hospital admissions among children <5 years of age (includes only data from the Municipal Children’s Infectious Diseases Hospital, which conducted consistent surveillance since September 2009), Moldova, September 2009–July 2014. B, Rotavirus-positive hospital admissions by age, Moldova, September 2009–July 2014. Abbreviation: RV, rotavirus.

Figure 3.

Percentage reduction in rotavirus hospitalizations and any-dose vaccine coverage in the first and second years following vaccine introduction, by age, Moldova, August 2012–July 2014.

Figure 4.

Vaccine effectiveness (VE) percent estimates against rotavirus hospitalization by severity score, Moldova, August 2012–July 2014. All VE estimates control for hospital and age group.