BACKGROUND:

Rotavirus remains an important cause of gastroenteritis and has been associated with the hospitalization of 34 to 53 per 10 000 children <5 years of age in the United States annually from 2008 to 2012. Rotavirus vaccines are underused compared with other routine vaccines. We describe rotavirus vaccine coverage and missed opportunities for rotavirus vaccination.

METHODS:

The National Immunization Survey is a random-digit–dial, population-based survey including US children 19 to 35 months of age. Children fully vaccinated for rotavirus were those who received 3 doses of the pentavalent rotavirus vaccine, 2 doses of the monovalent rotavirus vaccine, or ≥3 doses of either vaccine type. Doses of the diphtheria-tetanus-acellular pertussis vaccine received from 6 weeks through 8 months and 0 days of age when the rotavirus vaccine was not received were considered missed opportunities for rotavirus vaccination according to Advisory Committee on Immunization Practices (ACIP) guidelines, and doses of the diphtheria-tetanus-acellular pertussis vaccine or measles-mumps-rubella vaccine from 6 weeks through 24 months and 0 days of age were considered missed opportunities according to World Health Organization recommendations.

RESULTS:

Of the 14 571 children included in the 2014 National Immunization Survey, 71% were fully vaccinated for rotavirus. Lower socioeconomic status increased the likelihood of being unvaccinated for rotavirus. Among the 14% of children who received no doses of the rotavirus vaccine, 72% had ≥1 ACIP-defined missed opportunities, and 83% had ≥1 World Health Organization–defined missed opportunities. Higher socioeconomic status increased the likelihood of having missed opportunities. Complete rotavirus vaccine coverage could be improved to 81% if all missed opportunities within the ACIP-recommended schedule were addressed.

CONCLUSIONS:

Addressing missed opportunities for rotavirus vaccination is essential to achieving the 80% rotavirus vaccine coverage target outlined by Healthy People 2020.

What’s Known on This Subject:

Rotavirus vaccines are underused compared with other routine childhood vaccines. Since their introduction in 2006, coverage has plateaued at ∼70%, whereas coverage for other routine childhood immunizations (eg, diphtheria-tetanus-acellular pertussis vaccine and pneumococcal conjugate vaccine) consistently exceeds 90%.

We describe risk factors for not receiving the rotavirus vaccine and missed opportunities for rotavirus vaccination among children included in the 2014 National Immunization Survey.

Before rotavirus vaccine introduction, rotavirus disease caused an estimated 200 000 emergency outpatient visits and 55 000 to 70 000 hospitalizations each year among children <5 years of age in the United States.1 Rotavirus vaccines, introduced in 2006 and 2008, reduced rotavirus-attributed hospitalizations by 70% to 80%.1,3 Effectiveness of the rotavirus vaccine in preventing hospitalization has been measured at 83% to 84% in the United States.2 Despite the success of rotavirus vaccines, rotavirus remains an important cause of severe gastroenteritis, resulting in the hospitalization of 34 to 53 per 10 000 children <5 years of age in the United States from 2008 to 2012.4 Vaccine coverage reports from the Centers for Disease Control and Prevention indicate that only ∼70% of vaccine-eligible children 19 to 35 months of age are completely vaccinated for rotavirus.3,5 In comparison, coverage for other vaccines given at the same ages, such as ≥3 doses of the diphtheria-tetanus-acellular pertussis (DTaP) vaccine and pneumococcal conjugate vaccine, exceeds 90%.5 Failure to vaccinate for rotavirus has been linked with rotavirus disease, and improving rotavirus vaccine uptake is a public health priority.6

The Advisory Committee on Immunization Practices (ACIP) recommends administration of the first dose of rotavirus vaccine no earlier than 6 weeks of age but no later than 14 weeks and 6 days of age with completion of the series by 8 months and 0 days of age.7 The age restrictions for rotavirus vaccine administration were informed by the history of rotavirus vaccine safety. The first licensed rotavirus vaccine, RotaShield (tetravalent rotavirus vaccine; Wyeth), was withdrawn from use in 1999 after association with 1 excess case of intussusception (telescoping of the bowel) in every 10 000 children vaccinated.8 Some data from children vaccinated with RotaShield suggested a possible association between late administration of rotavirus vaccine and increased risk of intussusception, which informed the current recommended rotavirus vaccine schedule.9,11 Two second-generation rotavirus vaccines have been developed and licensed in the United States since RotaShield was removed from the market. In 2006, a 3-dose, live-attenuated, pentavalent rotavirus vaccine (RV5) (RotaTeq; Merck) was licensed, and in 2008, a 2-dose, live-attenuated, monovalent rotavirus vaccine (RV1) (Rotarix; GlaxoSmithKline) became available. The 2 current licensed rotavirus vaccines (RV1 and RV5) are estimated to cause 1 to 6 excess cases of intussusception per 100 000 vaccinated.12 Given the substantial decrease in rotavirus morbidity and mortality since vaccine introduction, the benefits of rotavirus vaccination outweigh this small excess risk of intussusception.13,14 Globally, particularly in low-resource settings, initiating and completing vaccination before 8 months of age is impractical.12 In 2013, the World Health Organization (WHO) recommended initiating rotavirus vaccination up to 24 months of age, noting that potential benefits of vaccination would outweigh the small safety risks associated with the vaccination of older children.15 We assessed both the ACIP- and WHO-defined missed opportunities for rotavirus vaccination to consider the potential for rotavirus vaccines in as broad of a context as possible.

The DTaP combination vaccine is considered the backbone of vaccine coverage in the United States, and the first 3 doses are recommended at 2, 4, and 6 months of age. This correlates with the recommended schedule for rotavirus immunization. RV1 is a 2-dose vaccine recommended at 2 and 4 months of age, and RV5 is a 3-dose vaccine recommended at 2, 4, and 6 months of age. In this study, we evaluate missed opportunities for children to receive the rotavirus vaccine by identifying doses of DTaP vaccine that were administered within the ACIP-recommended rotavirus vaccine schedule without administration of the rotavirus vaccine. To evaluate the potential impact of expanding rotavirus vaccination according to WHO recommendations, we also considered doses of the measles-mumps-rubella (MMR) vaccine given up to 24 months of age as an opportunity to administer rotavirus vaccine.16 The initial dose of MMR vaccine is recommended at ages 12 to 15 months.7 Consistently high coverage and the recommended vaccination schedule make it a useful target for simultaneous rotavirus vaccination.

This study was deemed not to be human subjects research by the Emory University Institutional Review Board. All analyses were conducted by using the 2014 National Immunization Survey (NIS) data set.17 Briefly, the NIS is a 2-phase, nationally representative telephone survey of parents of US children 19 to 35 months of age. Initially, parents are contacted by random-digit dialing to obtain their children’s vaccine history and demographic information. After contact with parents, vaccine providers are contacted to verify vaccine information. Only provider-verified immunization data were included in this study.

Completely vaccinated children were those who received 3 doses of RV5, 2 doses of RV1, or ≥3 doses of mixed RV1 and RV5. Partially vaccinated children were those who received 1 or 2 doses of RV5, 1 dose of RV1, or a 2-dose mixed series (RV1 and RV5). Unvaccinated children were those who received no doses of the rotavirus vaccine. Three-dose DTaP vaccine coverage was estimated for comparison with rotavirus vaccine coverage.

Health care encounters wherein DTaP vaccine was given were considered an opportunity to simultaneously vaccinate for rotavirus. Doses of DTaP vaccine received from 6 weeks through 14 weeks and 6 days of age, with no concomitant rotavirus vaccination, were considered missed opportunities for rotavirus vaccine initiation. DTaP vaccine doses received from 15 weeks through 8 months and 0 days of age were considered missed opportunities for rotavirus vaccine doses 2 or 3.

Vaccination with DTaP vaccine or MMR vaccine from 6 weeks through 24 months and 0 days of age, with no concomitant rotavirus vaccination, was considered a missed opportunity to simultaneously vaccinate for rotavirus according to WHO recommendations because the WHO does not have age restrictions for the administration of rotavirus vaccines.

All analyses were conducted by using SAS 9.4 (SAS Institute, Inc, Cary, NC) and weights included in the NIS data set. Weighting procedures and variables were applied as described in the NIS data user’s guide.18 SAS procedures specific to complex survey methods were used to determine proportions, odds ratios, and associated confidence intervals. Estimates of vaccine coverage and missed opportunities were stratified by child and maternal demographic variables of interest available in the NIS data set (Tables 1 and 2). Adjusted and unadjusted estimates of vaccine coverage and missed opportunities were determined by using logistic regression. Adjusted models included factors thought to be associated with vaccine coverage or missed opportunities, and covariables were retained according to stepwise regression with backward elimination.3,6,19,20 Because adjusted odds ratios were considered nominally different from unadjusted estimates, they are not presented in results but are available in Supplemental Table 4.

TABLE 1

Stratified Summary of Rotavirus Vaccination Among Children Included in the 2014 NIS (19–35 Months of Age)

%Unvaccinated, %Partially Vaccinated, %Fully Vaccinated, %Unvaccinated Versus Fully Vaccinated, OR (95% CI)Partially Versus Fully Vaccinated, OR (95% CI)
Overall 100.0 13.9 15.3 70.7 a a
Child demographics
Race and/or ethnicity
Hispanic 25.7 10.7 17.5 71.8 0.8 (0.6–1.0) 1.5 (1.2–2.0)
Non-Hispanic white 47.6 14.0 11.9 74.0 Reference Reference
Non-Hispanic African American 13.6 17.5 25.0 57.5 1.6 (1.2–2.1) 2.7 (2.1–3.5)
Non-Hispanic multiracial and/or other 13.1 16.4 13.2 70.4 1.2 (0.9–1.6) 1.2 (0.8–1.6)
No. children in household
1 28.4 12.4 12.8 74.8 Reference Reference
2 or 3 56.4 12.6 14.9 72.5 1.1 (0.8–1.3) 1.2 (0.9–1.6)
≥4 15.2 21.6 21.7 56.7 2.3 (1.7–3.1) 2.2 (1.6–3.1)
Maternal demographics
Education
<12 y 17.6 15.9 18.2 65.8 1.7 (1.3–2.3) 2.6 (1.9–3.4)
12 y 24.9 16.8 19.3 63.9 1.9 (1.5–2.4) 2.8 (2.2–3.6)
>12 y, not college graduate 23.9 13.4 18.4 68.2 1.4 (1.1–1.8) 2.5 (1.9–3.3)
College graduate 33.6 11.1 8.7 80.2 Reference Reference
Socioeconomic characteristics
Poverty status
Above poverty, >$75 000 27.4 10.7 7.3 82.0 0.7 (0.5–0.8) 0.4 (0.3–0.6) Above poverty, ≤$75 000 33.9 13.8 15.2 71.0 Reference Reference
Below poverty 33.4 16.8 21.9 61.4 1.4 (1.1–1.8) 1.7 (1.3–2.1)
Unknown 5.4 a a a a a
Uninsured at any point
Yes 9.4 19.3 18.4 62.3 1.8 (1.3–2.5) 1.4 (1.0–2.0)
No 89.8 12.3 15.0 72.7 Reference Reference
Unknown 0.7 a a a a a
Provider characteristics: facility type
All public 11.7 15.7 19.2 65.1 1.6 (1.2–2.2) 1.8 (1.3–2.6)
All hospital 12.6 19.5 14.9 65.6 2.0 (1.5–2.5) 1.4 (1.1–1.8)
All private 55.7 11.5 12.3 76.1 Reference Reference
Military and/or other 3.1 15.5 22.5 62.1 1.6 (0.7–3.7) 2.1 (1.6–2.7)
Mixed 16.8 12.1 22.3 65.6 1.2 (0.9–1.6) 2.2 (1.2–4.3)
%Unvaccinated, %Partially Vaccinated, %Fully Vaccinated, %Unvaccinated Versus Fully Vaccinated, OR (95% CI)Partially Versus Fully Vaccinated, OR (95% CI)
Overall 100.0 13.9 15.3 70.7 a a
Child demographics
Race and/or ethnicity
Hispanic 25.7 10.7 17.5 71.8 0.8 (0.6–1.0) 1.5 (1.2–2.0)
Non-Hispanic white 47.6 14.0 11.9 74.0 Reference Reference
Non-Hispanic African American 13.6 17.5 25.0 57.5 1.6 (1.2–2.1) 2.7 (2.1–3.5)
Non-Hispanic multiracial and/or other 13.1 16.4 13.2 70.4 1.2 (0.9–1.6) 1.2 (0.8–1.6)
No. children in household
1 28.4 12.4 12.8 74.8 Reference Reference
2 or 3 56.4 12.6 14.9 72.5 1.1 (0.8–1.3) 1.2 (0.9–1.6)
≥4 15.2 21.6 21.7 56.7 2.3 (1.7–3.1) 2.2 (1.6–3.1)
Maternal demographics
Education
<12 y 17.6 15.9 18.2 65.8 1.7 (1.3–2.3) 2.6 (1.9–3.4)
12 y 24.9 16.8 19.3 63.9 1.9 (1.5–2.4) 2.8 (2.2–3.6)
>12 y, not college graduate 23.9 13.4 18.4 68.2 1.4 (1.1–1.8) 2.5 (1.9–3.3)
College graduate 33.6 11.1 8.7 80.2 Reference Reference
Socioeconomic characteristics
Poverty status
Above poverty, >$75 000 27.4 10.7 7.3 82.0 0.7 (0.5–0.8) 0.4 (0.3–0.6) Above poverty, ≤$75 000 33.9 13.8 15.2 71.0 Reference Reference
Below poverty 33.4 16.8 21.9 61.4 1.4 (1.1–1.8) 1.7 (1.3–2.1)
Unknown 5.4 a a a a a
Uninsured at any point
Yes 9.4 19.3 18.4 62.3 1.8 (1.3–2.5) 1.4 (1.0–2.0)
No 89.8 12.3 15.0 72.7 Reference Reference
Unknown 0.7 a a a a a
Provider characteristics: facility type
All public 11.7 15.7 19.2 65.1 1.6 (1.2–2.2) 1.8 (1.3–2.6)
All hospital 12.6 19.5 14.9 65.6 2.0 (1.5–2.5) 1.4 (1.1–1.8)
All private 55.7 11.5 12.3 76.1 Reference Reference
Military and/or other 3.1 15.5 22.5 62.1 1.6 (0.7–3.7) 2.1 (1.6–2.7)
Mixed 16.8 12.1 22.3 65.6 1.2 (0.9–1.6) 2.2 (1.2–4.3)
TABLE 2

Summary of Missed Opportunities for Rotavirus Vaccination Among Children Included in the 2014 NIS (19–35 Months of Age)

%Missed Opportunity, 8 mo 0 d, %Missed Opportunity, 24 mo 0 d, %Missed Opportunity Versus None, 8 mo 0 d, OR (95% CI)Missed Opportunity Versus None, 24 mo 0 d, OR (95% CI)
Child demographics 100.0 — — — —
Race and/or ethnicity
Hispanic 25.7 69.1 78.9 0.9 (0.8–1.1) 1.0 (0.8–1.3)
Non-Hispanic white 47.6 70.9 78.7 Reference Reference
Non-Hispanic African American 13.6 65.7 79.0 0.8 (0.6–1.0) 1.0 (0.8–1.3)
Non-Hispanic multiracial and/or other 13.1 68.1 76.2 0.9 (0.7–1.1) 0.9 (0.7–1.1)
No. children in household
1 28.4 69.9 75.9 Reference Reference
2 or 3 56.4 69.2 78.4 1.0 (0.8–1.2) 1.2 (1.0–1.4)
≥4 15.2 69.2 83.5 1.0 (0.8–1.2) 1.6 (1.3–2.1)
Maternal demographics
Education
<12 y 17.6 64.8 77.7 0.6 (0.5–0.7) 0.8 (0.7–1.1)
12 y 24.9 66.7 77.2 0.7 (0.5–0.8) 0.8 (0.7–1.0)
>12 y, not college graduate 23.9 67.2 77.3 0.7 (0.6–0.8) 0.8 (0.7–1.0)
College graduate 33.6 75.4 80.6 Reference Reference
Socioeconomic characteristics
Poverty status
Above poverty, >$75 000 27.4 74.2 78.8 1.2 (1.0–1.5) 1.0 (0.9–1.3) Above poverty, ≤$75 000 33.9 70.4 78.0 Reference Reference
Below poverty 33.4 65.1 79.1 0.8 (0.7–0.9) 1.1 (0.9–1.3)
Unknown 5.4 64.9 75.5 0.8 (0.6–1.1) 0.9 (0.6–1.3)
Uninsured at any point
Yes 9.4 63.5 76.3 0.7 (0.5–0.9) 0.8 (0.6–1.2)
No 89.8 70.9 79.2 Reference Reference
Unknown 0.7 a a a a
Provider characteristics: facility type
All public 11.7 62.2 72.7 0.6 (0.5–0.8) 0.6 (0.5–0.9)
All hospital 12.6 58.6 69.3 0.5 (0.4–0.6) 0.5 (0.4–0.7)
All private 55.7 73.3 80.8 Reference Reference
Military and/or other 3.1 75.1 89.5 0.9 (0.7–1.1) 1.2 (0.9–1.5)
Mixed 16.8 71.6 83.1 1.1 (0.7–1.8) 2.0 (1.3–3.2)
%Missed Opportunity, 8 mo 0 d, %Missed Opportunity, 24 mo 0 d, %Missed Opportunity Versus None, 8 mo 0 d, OR (95% CI)Missed Opportunity Versus None, 24 mo 0 d, OR (95% CI)
Child demographics 100.0 — — — —
Race and/or ethnicity
Hispanic 25.7 69.1 78.9 0.9 (0.8–1.1) 1.0 (0.8–1.3)
Non-Hispanic white 47.6 70.9 78.7 Reference Reference
Non-Hispanic African American 13.6 65.7 79.0 0.8 (0.6–1.0) 1.0 (0.8–1.3)
Non-Hispanic multiracial and/or other 13.1 68.1 76.2 0.9 (0.7–1.1) 0.9 (0.7–1.1)
No. children in household
1 28.4 69.9 75.9 Reference Reference
2 or 3 56.4 69.2 78.4 1.0 (0.8–1.2) 1.2 (1.0–1.4)
≥4 15.2 69.2 83.5 1.0 (0.8–1.2) 1.6 (1.3–2.1)
Maternal demographics
Education
<12 y 17.6 64.8 77.7 0.6 (0.5–0.7) 0.8 (0.7–1.1)
12 y 24.9 66.7 77.2 0.7 (0.5–0.8) 0.8 (0.7–1.0)
>12 y, not college graduate 23.9 67.2 77.3 0.7 (0.6–0.8) 0.8 (0.7–1.0)
College graduate 33.6 75.4 80.6 Reference Reference
Socioeconomic characteristics
Poverty status
Above poverty, >$75 000 27.4 74.2 78.8 1.2 (1.0–1.5) 1.0 (0.9–1.3) Above poverty, ≤$75 000 33.9 70.4 78.0 Reference Reference
Below poverty 33.4 65.1 79.1 0.8 (0.7–0.9) 1.1 (0.9–1.3)
Unknown 5.4 64.9 75.5 0.8 (0.6–1.1) 0.9 (0.6–1.3)
Uninsured at any point
Yes 9.4 63.5 76.3 0.7 (0.5–0.9) 0.8 (0.6–1.2)
No 89.8 70.9 79.2 Reference Reference
Unknown 0.7 a a a a
Provider characteristics: facility type
All public 11.7 62.2 72.7 0.6 (0.5–0.8) 0.6 (0.5–0.9)
All hospital 12.6 58.6 69.3 0.5 (0.4–0.6) 0.5 (0.4–0.7)
All private 55.7 73.3 80.8 Reference Reference
Military and/or other 3.1 75.1 89.5 0.9 (0.7–1.1) 1.2 (0.9–1.5)
Mixed 16.8 71.6 83.1 1.1 (0.7–1.8) 2.0 (1.3–3.2)

—, not applicable.

a

Estimate not included.

We also performed a sensitivity analysis to estimate the potential increase in rotavirus vaccine coverage that may be achieved by improving the linkage between DTaP (or MMR) and rotavirus vaccine administration. For this analysis only, complete rotavirus vaccination was conservatively considered as 3 doses of rotavirus vaccine because RV5 is the most frequently used rotavirus vaccine in the United States.

The 2014 NIS included 24 897 children. We excluded children without provider-verified data (N = 9838) and those who had received a rotavirus vaccine of unknown type (N = 488), resulting in 14 571 children (59%) being included in this analysis. Of these children, 71% were fully vaccinated for rotavirus, 15% were partially vaccinated, and 14% were unvaccinated. Among fully vaccinated children, 72% received RV5, 27% received RV1, and <1% received a mixed schedule (doses of RV1 and RV5). Among partially vaccinated children, 73% received 1 or 2 doses of RV5, 11% received a single dose of RV1, and 16% received 1 dose of each vaccine type.

Stratified estimates of rotavirus vaccine coverage indicated that coverage varied by socioeconomic factors. Children whose mothers were not college graduates, in households with ≥4 children, who received vaccines in a nonprivate clinic, and who had been uninsured at any point had an increased likelihood of being unvaccinated for rotavirus (Table 1). Racial differences in rotavirus vaccine coverage were evident, with African American children being at increased risk of being unvaccinated.

Stratified estimates of partial rotavirus vaccine coverage indicate that the risk factors for partial vaccination are similar to those associated with being unvaccinated for rotavirus. Low socioeconomic status and racial/ethnic minority status increased the likelihood of being partially rather than fully vaccinated (Table 1).

For comparison, risk factors associated with not having received 3 doses of DTaP were also determined. Indicators of lower socioeconomic status were significantly associated with failure to receive 3-dose DTaP vaccination (Supplemental Table 4).

FIGURE 1

Flowchart of missed opportunities for rotavirus vaccination among children 19 to 35 months of age included in the 2014 NIS.

FIGURE 1

Flowchart of missed opportunities for rotavirus vaccination among children 19 to 35 months of age included in the 2014 NIS.

Close modal

Among children who were unvaccinated for rotavirus, 83% had ≥1 missed opportunity to receive rotavirus vaccine between 15 weeks and 24 months of age, and 75% had ≥2 missed opportunities (Fig 1). Among partially vaccinated children, 96% had ≥1 missed opportunity, and 86% had ≥2 missed opportunities for rotavirus vaccination between 15 weeks and 24 months of age. Children were more likely to have had missed opportunities up to 24 months of age if there were other children in the household or if they received vaccines from mixed provider types (Table 2).

Complete rotavirus vaccine coverage could be improved from 71% to 81% if all missed opportunities within the ACIP-recommended schedule were addressed. We found that 94% rotavirus vaccine coverage could be achieved if all missed opportunities within the WHO-recommended schedule were addressed (Table 3).

TABLE 3

Sensitivity Analysis of Potential Rotavirus Vaccine Coverage Given Conditions of Increased Rotavirus Vaccine Use Among Children With Missed Opportunities to Receive the Vaccine

ACIP Rotavirus Vaccination Through 8 mo of AgeWHO Rotavirus Vaccination Through 24 mo of Age
Unvaccinated children (14%)
— 70.7 — 70.7
25 1.8 72.5 25 2.4 73.1
50 3.6 74.3 50 4.8 75.5
75 5.4 76.1 75 7.2 77.9
100 7.2 77.9 100 9.6 80.3
Partially vaccinated children (15%)
— 70.7 — 70.7
25 0.9 71.6 25 3.3 74.0
50 1.8 72.5 50 6.6 77.3
75 2.7 73.4 75 9.9 80.6
100 3.6 74.3 100 13.2 83.9
Overall
— 70.7 — 70.7
25 2.7 73.4 25 5.7 76.4
50 5.4 76.1 50 11.4 82.1
75 8.1 78.8 75 17.1 87.8
100 10.8 81.5 100 22.8 93.5
ACIP Rotavirus Vaccination Through 8 mo of AgeWHO Rotavirus Vaccination Through 24 mo of Age
Unvaccinated children (14%)
— 70.7 — 70.7
25 1.8 72.5 25 2.4 73.1
50 3.6 74.3 50 4.8 75.5
75 5.4 76.1 75 7.2 77.9
100 7.2 77.9 100 9.6 80.3
Partially vaccinated children (15%)
— 70.7 — 70.7
25 0.9 71.6 25 3.3 74.0
50 1.8 72.5 50 6.6 77.3
75 2.7 73.4 75 9.9 80.6
100 3.6 74.3 100 13.2 83.9
Overall
— 70.7 — 70.7
25 2.7 73.4 25 5.7 76.4
50 5.4 76.1 50 11.4 82.1
75 8.1 78.8 75 17.1 87.8
100 10.8 81.5 100 22.8 93.5

Most children who are unvaccinated for rotavirus had at least 1 missed opportunity to receive the rotavirus vaccine. We estimated a ∼10% increase in complete rotavirus vaccination to 81% coverage if all identified missed opportunities for simultaneous DTaP and rotavirus vaccination within the current ACIP schedule were addressed.21 Approximately two-thirds of this improvement in coverage is possible with the complete vaccination of children who are currently unvaccinated against rotavirus, and less improvement would be achieved by targeting partially vaccinated children (Table 3). Addressing all identified missed opportunities could close the gap between current rotavirus vaccine coverage and the Healthy People 2020 goal of 80% complete coverage. We found that children from higher-income households and those whose mothers had achieved a college degree were more likely to have missed opportunities for rotavirus vaccination within the ACIP-recommended schedule. Parental vaccine hesitancy, specifically among mothers with a college level of education, has been described.22,25 We had no way of determining from the NIS if failure to receive the rotavirus vaccine at the time a child was eligible was due to parental refusal or provider failure to offer it. Either way, it is a missed opportunity; however, addressing the 2 different causes would involve different interventions.

Characteristics of children who are unvaccinated for rotavirus differed from those associated with missed opportunities to receive the vaccine. Although higher household income and college education were correlated with missed opportunities, lower educational achievement, uninsured status, and having ≥4 children in the household correlated with failure to receive the rotavirus vaccine. DTaP coverage was also lower among those of lower socioeconomic status, suggesting that socioeconomic factors play an important role in failure to receive routine vaccines, including the rotavirus vaccine. Because low socioeconomic status has also been associated with an increased risk of rotavirus-attributed hospitalization, preserving access to vaccines (eg, US Vaccines for Children Program) and identifying ways to further improve vaccination rates in these at-risk children is a high priority.20,26

Rotavirus vaccination is effective in the prevention of severe gastroenteritis, and failure to vaccinate has been linked with rotavirus disease.27 Rotavirus disease in the United States has developed a biennial pattern since vaccine introduction. The increase in rotavirus disease observed every other year may be attributable to dynamics of community protection (indirect protection).28,29 Because only ∼70% of vaccine-eligible children in the United States are fully vaccinated for rotavirus, it may take 2 years for a sufficient population of rotavirus-susceptible children to accumulate and amplify rotavirus transmission as opposed to annual outbreaks before vaccine introduction. Interestingly, these biennial peaks of disease have not been observed in countries with higher rotavirus vaccine coverage. In Australia and Finland, where vaccine coverage exceeds 90%, rotavirus disease prevalence remained low after vaccine introduction.30,31 Addressing the underuse of the rotavirus vaccine in the United States may eliminate the current biennial surges in rotavirus disease.

We also explored the impact of vaccinating older children according to WHO recommendations. We found that linking rotavirus vaccination with DTaP or MMR vaccination up to 24 months of age could result in rotavirus vaccine coverage as high as 94%. Expansion of the schedule for rotavirus vaccination in the United States could decrease the burden of rotavirus disease while also setting an important precedent for global rotavirus vaccine use.

Missed opportunities for rotavirus vaccination are common among US children. Low rotavirus vaccine uptake may be attributable to both socioeconomic barriers and possibly vaccine hesitancy. Understanding the barriers to rotavirus vaccine uptake and developing effective public health measures to promote vaccine use will be essential to reducing rotavirus morbidity in the United States. Complete rotavirus vaccination is limited at ∼81% by the current ACIP-recommended rotavirus schedule as assessed by using missed opportunities. Improving rotavirus vaccination coverage to ∼90%, which is comparable to DTaP and other established routine childhood immunizations, does not appear possible with the current ACIP-recommended rotavirus vaccine schedule based on the identified missed opportunities.

For sensitivity analysis, complete vaccination was considered 3+ doses, and partial vaccination was considered 1 to 2 doses of the rotavirus vaccine. —, not applicable.

Dr Bednarczyk conceptualized and designed the study, reviewed and revised the manuscript, and supervised data analyses; Dr Anderson conceptualized and designed the study and reviewed and revised the manuscript; Dr Orenstein critically reviewed the manuscript, suggested further data analysis and key revisions, and contributed important intellectual input; Dr Yi critically reviewed the manuscript and offered important intellectual input; Ms Sederdahl conducted data analyses, drafted the initial manuscript, and reviewed and revised the manuscript; and all authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.

FUNDING: No external funding.

ACIP

DTaP

diphtheria-tetanus-acellular pertussis

MMR

measles-mumps-rubella

NIS

National Immunization Survey

RV1

monovalent rotavirus vaccine

RV5

pentavalent rotavirus vaccine

WHO

World Health Organization

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## Competing Interests

POTENTIAL CONFLICT OF INTEREST: Dr Anderson has received personal fees from AbbVie for consulting, funds to conduct clinical research from Merck, and his institution receives funds to conduct clinical research from MedImmune, Regeneron Pharmaceuticals, PaxVax Corporation, Pfizer, Merck, Novavax, Sanofi Pasteur, and Micron Technology; the other authors have indicated they have no potential conflicts of interest to disclose.

FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.