Update on Vaccine-Derived Poliovirus Outbreaks - Democratic Republic of the Congo and Horn of Africa, 2017-2018.

Widespread use of live attenuated (Sabin) oral poliovirus vaccine (OPV) has resulted in marked progress toward global poliomyelitis eradication (1). However, in underimmunized populations, extensive person-to-person transmission of Sabin poliovirus can result in genetic reversion to neurovirulence and paralytic vaccine-derived poliovirus (VDPV) disease (1). This report updates (as of February 26, 2019) previous reports on circulating VDPV type 2 (cVDPV2) outbreaks during 2017-2018 in the Democratic Republic of the Congo (DRC) and in Somalia, which experienced a concurrent cVDPV type 3 (cVDPV3) outbreak* (2,3). In DRC, 42 cases have been reported in four cVDPV2 outbreaks; paralysis onset in the most recent case was October 7, 2018 (2). Challenges to interrupting transmission have included delays in outbreak-response supplementary immunization activities (SIAs) and difficulty reaching children in all areas. In Somalia, cVDPV2 and cVDPV3 were detected in sewage before the detection of paralytic cases (3). Twelve type 2 and type 3 cVDPV cases have been confirmed; the most recent paralysis onset dates were September 2 (cVDPV2) and September 7, 2018 (cVDPV3). The primary challenge to interrupting transmission is the residence of >300,000 children in areas that are inaccessible for vaccination activities. For both countries, longer periods of surveillance are needed before interruption of cVDPV transmission can be inferred.

Monovalent Rotavirus Vaccine Effectiveness and Impact on Rotavirus Hospitalizations in Zanzibar, Tanzania: Data From the First 3 Years After Introduction.

Background: Low-income settings challenge the level of protection provided by live attenuated oral rotavirus vaccines. Rotarix (RV1) was introduced in the United Republic of Tanzania in early 2013, with 2 doses given at the World Health Organization-recommended schedule of ages 6 and 10 weeks, along with oral poliovirus vaccine. Methods: We performed active surveillance for rotavirus hospitalizations at the largest hospital in Zanzibar, Tanzania, from 2010 through 2015. Using a case-test-negative control design, we estimated the vaccine effectiveness (VE) of 2 RV1 doses in preventing rotavirus hospitalizations. Results: Based on 204 rotavirus case patients and 601 test-negative controls aged 5-23 months, the VE of 2 RV1 doses against hospitalization for rotavirus diarrhea was 57% (95% confidence interval, 14%-78%). VE tended to increase against hospitalizations with higher severity, reaching 69% (95% confidence interval, 15%-88%) against the severity score for the top quarter of case patients. Compared with the prevaccine period, there were estimated reductions of 40%, 46%, and 69% in the number of rotavirus hospitalizations among infants in 2013, 2014, and 2015, respectively, and reductions of 36%, 26%, and 64%, respectively, among children aged <5 years. Conclusions: With data encompassing 3 years before and 3 years after vaccine introduction, our results indicate that successful delivery of RV1 on the current World Health Organization schedule can provide substantial health benefits in a resource-limited setting.

Intussusception among infants in Tanzania: findings from prospective hospital-based surveillance, 2013-2016.

INTRODUCTION: intussusception surveillance was initiated in Tanzania in 2013 after monovalent rotavirus vaccine was introduced, as part of the 7-country African evaluation to assess whether the vaccine was associated with an increased risk of intussusception. An increased risk from vaccine was not identified. Published data on intussusception in Tanzanian infants are limited. METHODS: prospective intussusception surveillance was conducted at 7 referral hospitals during 2013-2016 to identify all infants with intussusception meeting Brighton Level 1 criteria. Demographic, household and clinical data were collected by hospital clinicians and analyzed. RESULTS: a total of 207 intussusception cases were identified. The median age of cases was 5.8 months and nearly three-quarters were aged 4-7 months. Median number of days from symptom onset to admission at treatment hospital was 3 (IQR 2-5). Seventy-eight percent (152/195) of cases had been admitted at another hospital before transfer to the treating hospital. Enema reduction was not available; all infants were treated surgically and 55% (114/207) had intestinal resection. The overall case-fatality rate was 30% (62/206). Compared with infants who survived, those who died had longer duration of symptoms before admission to treatment hospital (median 4 vs 3 days; p < 0.01), higher rate of intestinal resection (81% [60/82] vs 44% [64/144], p < 0.001), and from families with lower incomes (i.e., less likely to own a television [p < 0.01] and refrigerator [p < 0.05). CONCLUSION: Tanzanian infants who develop intussusception have a high case-fatality rate. Raising the index of suspicion among healthcare providers, allocating resources to allow wider availability of abdominal ultrasound for earlier diagnosis, and training teams in ultrasound-guided enema reduction techniques used in other African countries could reduce the fatality rate.

Trends in diarrhea hospitalizations among infants at three hospitals in Tanzania before and after rotavirus vaccine introduction.

BACKGROUND: The Tanzania Ministry of Health introduced monovalent human rotavirus vaccine in January 2013, to be administered at ages 6 and 10 weeks. Data suggest there was high vaccine uptake. We used hospital ward registers from 3 hospitals to examine trends in diarrhea hospitalizations among infants before and after vaccine introduction. METHODS: Ward registers from Dodoma Regional Referral Hospital (Central Tanzania), and two hospitals in Mbeya (Southwest area), Mbeya Zonal Referral Hospital and Mbalizi Hospital, were used to tally admissions for diarrhea among children by age group, month and year. Rotavirus surveillance had started at these hospitals in early 2013; the proportion of infants enrolled and rotavirus-EIA positive were examined by month to determine peak periods of rotavirus disease post-vaccine introduction. RESULTS: Registers were available for 2-4 prevaccine years and 2-3 post introduction years. At Dodoma Regional Referral Hospital, compared with the mean of 2011 and 2012, diarrhea hospitalizations among infants were 26% lower in 2015 and 58% lower in 2016. The diarrhea peak shifted later in the year first by 1 and then by 2-3 months from prevaccine. At the Mbeya hospitals, the number of diarrhea admissions in prevaccine period varied substantially by year. At Mbeya Referral Hospital, diarrhea hospitalizations among infants were lower by 25-37% in 2014 and 11-26% in 2015, while at Mbalizi Hospital, these hospitalizations were 4% lower in 2014 and 14% higher in 2015. Rotavirus testing data demonstrated a lowering of the prevaccine peak, a shift in timing of the peak months and indicated that other diarrheal peaks in post-introduction years were not due to rotavirus. CONCLUSIONS: In this ecological evaluation, total diarrhea hospitalizations among infants were lower (≥25% lower in ≥1 year) following introduction in 2 of 3 hospitals. There are challenges in using ward registers to ascertain possible impact of rotavirus vaccine introduction on trends in hospitalizations for treatment of all diarrheal illness.

Detection of rotavirus before and after monovalent rotavirus vaccine introduction and vaccine effectiveness among children in mainland Tanzania.

BACKGROUND: Monovalent rotavirus vaccine (RV1) was introduced in Tanzania in January 2013 under the Reach Every Child initiative, to be given at ages 6 and 10 weeks. We used the sentinel hospital rotavirus surveillance system to examine the rotavirus detection rate before and after vaccine introduction and estimate vaccine effectiveness. METHODS: Before vaccine introduction, rotavirus surveillance was established at two mainland hospitals; children admitted for acute diarrhea were eligible for enrollment and stools were tested for rotavirus antigen. We compared the rotavirus positivity rate in the pre-vaccine period (Tanga Hospital, 2009 and 2011; Bugando Medical Centre, 2012) to that from post-introduction years, 2014-2015. In 2013, surveillance was established at 9 additional hospitals. We examined rotavirus positivity among infants at these sites for 2014-2015. We obtained vaccine records and calculated vaccine effectiveness at 3 sites using case-test-negative control design. RESULTS: At Tanga Hospital, the rotavirus positivity rate among infants was 41% (102/251) pre-vaccine and 14% (28/197) in post-vaccine years (rate ratio: 0.35 [95% CI 0.22-0.54]). At Bugando, the positivity rate was 58% (83/143) pre-vaccine, and 18% (49/277) post-introduction (rate ratio 0.30 [95% CI 0.210.44]). Results were similar among children <5 years. At the new sites, the median site rotavirus positivity rate among infants was 26% in 2014 (range 19-44%) and 18% in 2015 (range 16-33%). The effectiveness of ≥1 RV1 dose against rotavirus hospitalization among children 5-23 months was 53% (95% CI: -14, 81), and 66% (95% CI: 9-87) against hospitalization with intravenous rehydration. Following introduction, peak rotavirus activity occurred later in the year and appeared more concentrated in time. CONCLUSION: Rotavirus surveillance data from Tanzania indicate that the rotavirus positivity rate among children hospitalized with diarrhea that were enrolled was substantially reduced after vaccine introduction. Low positivity rates among infants were detected at hospitals across the country. Overall, the data support that rotavirus vaccine has been successfully introduced and is effective in Tanzanian children.

Improving the efficiency and standards of a National Immunization Program Review: lessons learnt from United Republic of Tanzania.

A National Immunization Program Review (NIP Review) is a comprehensive external assessment of the performance of a country's immunization programme. The number of recommended special-topic NIP assessments, such as those for vaccine introduction or vaccine management, has increased. These assessments often have substantial overlap with NIP reviews, raising concern about duplication. Innovative technical and management approaches, including integrating several assessments into one, were applied in the United Republic of Tanzania's 2015 NIP Review. These approaches and processes were documented and a post-Review survey and group discussion. The Tanzania Review found that integrating assessments so they can be conducted at one time was feasible and efficient. There are concrete approaches for successfully managing a Review that can be shared and practiced including having a well-planned desk review and nominating topic-leads. The use of tablets for data entry has the potential to improve Review data quality and timely analysis; however, careful team training is needed. A key area to improve was to better coordinate and link findings from the national-level and field teams.