Removing the age restrictions for rotavirus vaccination: a benefit-risk modeling analysis

Abstract

Background: To minimize potential risk of intussusception, the World Health Organization (WHO) recommended in 2009 that rotavirus immunization should be initiated by age 15 weeks and completed before 32 weeks. These restrictions could adversely impact vaccination coverage and thereby its health impact, particularly in developing countries where delays in vaccination often occur.

Methods and findings: We conducted a modeling study to estimate the number of rotavirus deaths prevented and the number of intussusception deaths caused by vaccination when administered on the restricted schedule versus an unrestricted schedule whereby rotavirus vaccine would be administered with DTP vaccine up to age 3 years. Countries were grouped on the basis of child mortality rates, using WHO data. Inputs were estimates of WHO rotavirus mortality by week of age from a recent study, intussusception mortality based on a literature review, predicted vaccination rates by week of age from USAID Demographic and Health Surveys, the United Nations Children's Fund (UNICEF) Multiple Indicator Cluster Surveys (MICS), and WHO-UNICEF 2010 country-specific coverage estimates, and published estimates of vaccine efficacy and vaccine-associated intussusception risk. On the basis of the error estimates and distributions for model inputs, we conducted 2,000 simulations to obtain median estimates of deaths averted and caused as well as the uncertainty ranges, defined as the 5th-95th percentile, to provide an indication of the uncertainty in the estimates. We estimated that in low and low-middle income countries a restricted schedule would prevent 155,800 rotavirus deaths (5th-95th centiles, 83,300-217,700) while causing potentially 253 intussusception deaths (76-689). In contrast, vaccination without age restrictions would prevent 203,000 rotavirus deaths (102,000-281,500) while potentially causing 547 intussusception deaths (237-1,160). Thus, removing the age restrictions would avert an additional 47,200 rotavirus deaths (18,700-63,700) and cause an additional 294 (161-471) intussusception deaths, for an incremental benefit-risk ratio of 154 deaths averted for every death caused by vaccine. These extra deaths prevented under an unrestricted schedule reflect vaccination of an additional 21%-25% children, beyond the 63%-73% of the children who would be vaccinated under the restricted schedule. Importantly, these estimates err on the side of safety in that they assume high vaccine-associated risk of intussusception and do not account for potential herd immunity or non-fatal outcomes.

Conclusions: Our analysis suggests that in low- and middle-income countries the additional lives saved by removing age restrictions for rotavirus vaccination would far outnumber the potential excess vaccine-associated intussusception deaths. Please see later in the article for the Editors' Summary.

Figure 1. Age distribution of rotavirus deaths among children under 5 y, by WHO mortality group.

Figure 2. Vaccine coverage for dose 1 of DTP by week of age and WHO mortality group based on the DHSs and UNICEF MICs.

Figure 3. Global analysis of the relationship between esimated number of rotavirus gastroenteritis deaths avoided versus intussusception deaths caused by removal of the age restrictions for rotavirus vaccination.

These estimates are from 2,000 simulations with each blue dot representing a potential estimate of rotavirus deaths prevented (y-axis) versus intussusception deaths caused (x-axis) from removal of the age restrictions given the uncertainty on the parameters in the model: rotavirus mortality, vaccine efficacy, vaccine coverage, intussusception incidence, intussusception risk from vaccine, and intussusception fatality. The black square represents the median estimate.

Figure 4. WHO region specific analysis of relationship between esimated number of rotavirus gastroenteritis deaths avoided versus intussusception deaths caused by removal of the age restrictions for rotavirus vaccination.

These estimates are from 2,000 simulations with each blue dot representing a potential estimate of rotavirus deaths prevented (y-axis) versus intussusception deaths caused (x-axis) from removal of the age restrictions given the uncertainty on the parameters in the model: rotavirus mortality, vaccine efficacy, vaccine coverage, intussusception incidence, intussusception risk from vaccine, and intussusception fatality. The black square represents the median estimate. Because group A countries with very low child mortality (i.e., high-income) represent <0.1% of the global rotavirus deaths, they were excluded from this analysis.