Direct, indirect, total, and overall effectiveness of the rotavirus vaccines for the prevention of gastroenteritis hospitalizations in privately insured US children, 2007-2010

Abstract

We demonstrate how direct, indirect, total, and overall effectiveness estimates and absolute benefits of rotavirus vaccines vary through the years following vaccine introduction. Privately insured US children in a large claims database were followed from age 8 months until they 1) experienced a hospitalization for rotavirus or acute gastroenteritis; 2) lost continuous health plan enrollment; 3) turned 20 months of age; or 4) reached the end of the study period. Vaccine effectiveness estimates in preventing rotavirus and acute gastroenteritis hospitalizations were estimated using Cox proportional hazards regression, stratified by calendar year and adjusted for birth month. Incidence rate differences were estimated to determine the absolute number of gastroenteritis hospitalizations prevented in the cohort. Among 905,718 children, 51%, 66%, 80%, and 86% received 1 or more doses of rotavirus vaccine in each year from 2007 to 2010. The direct vaccine effectiveness of 1 or more doses of rotavirus vaccine in preventing rotavirus gastroenteritis hospitalizations ranged from 87% to 92% each year. Accounting for indirect protection increased estimates of vaccine effectiveness by an additional 3%-8% among those vaccinated. Failing to account for population-level vaccine benefits in 2010, when circulation of rotavirus was low, could underestimate the sustained impact of the vaccine program.

Keywords: diarrhea; gastroenteritis; immunity, herd; pharmacoepidemiology; program effectiveness; rotavirus; rotavirus vaccines; use-effectiveness.

Figure 1.

Types of vaccine effectiveness as described by Halloran et al. (1). A vaccinated population will still have some individuals within the population who are unvaccinated because 100% vaccination coverage is generally never achieved. VE, vaccine effectiveness.

Figure 2.

Derivation of the unvaccinated population (population 1) and the vaccinated population (population 2) in the rotavirus vaccine effectiveness cohort study of US commercially insured infants and children 8–20 months of age, 2001–2005 and 2007–2010. Births were identified using International Classification of Diseases, Ninth Revision, Clinical Modification, codes in inpatient and outpatient records. These records were restricted to infants 0 years of age and to females 10–50 years of age. Twenty-three of 905,718 infants were excluded from this cohort in the final rotavirus gastroenteritis analysis because their cohort entry date (8-month birthday) equaled their cohort exit date (rotavirus gastroenteritis hospitalization date (n = 4) or loss of health plan enrollment date (n = 19)); for the same reasons, 40 infants were excluded from the final acute gastroenteritis analysis. DTaP, diphtheria, tetanus, and acellular pertussis vaccine; RV1, monovalent rotavirus vaccine; RV5, pentavalent rotavirus vaccine.

Figure 3.

A) Incidence of rotavirus gastroenteritis (RGE) hospitalizations per 10,000 child-years among commercially insured US infants and children 8–20 months of age, individual years following vaccine introduction (2007–2010) versus prevaccine years combined (2001–2005). Solid line, 2001–2005; dashed and dotted line, 2007; small dashed line, 2008; large dashed line, 2009; dotted line, 2010. B) Incidence of RGE hospitalizations per 10,000 child-years among commercially insured US infants and children 8–20 months of age, individual prevaccine years (2001–2005). Solid line, 2001; dashed and dotted line, 2002; small dashed line, 2003; large dashed line, 2004; dotted line, 2005.

Figure 4.

Diarrhea-related hospitalizations per 10,000 children among commercially insured US infants, 8–20 months of age, in the pre–rotavirus vaccine period (2001–2005) and rotavirus vaccine period (2007–2010). Solid black line, rotavirus (International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM), code 008.61); small black dashed line, viral excluding rotavirus (ICD-9-CM codes 008.6 and 008.8, excluding 008.61); large black dashed line, bacterial (ICD-9-CM codes 001–005 and 008.0–008.5, excluding 003.2); hollow dashed line, presumed infectious (ICD-9-CM codes 009.0–009.3); dotted line, presumed noninfectious (ICD-9-CM code 558.9); dashed and dotted line, diarrhea otherwise specified (ICD-9-CM code, 787.91).

Figure 5.

A) Incidence of acute gastroenteritis (AGE) hospitalizations per 10,000 child-years among commercially insured US infants and children, 8–20 months of age, individual years following vaccine introduction (2007–2010) versus prevaccine years combined (2001–2005). Solid line, 2001–2005; dashed and dotted line, 2007; small dashed line, 2008; large dashed line, 2009; dotted line, 2010. B) Incidence of AGE hospitalizations per 10,000 child-years among commercially insured US infants and children, 8–20 months of age, individual prevaccine years (2001–2005). Solid line, 2001; dashed and dotted line, 2002; small dashed line, 2003; large dashed line, 2004; dotted line, 2005.