Intussusception and rotavirus vaccination: a review of the available evidence

Intussusception risk following oral monovalent rotavirus vaccination in 3 Asian countries: A self-control case series evaluation

Rotavirus vaccines have substantially decreased rotavirus hospitalizations in countries where they have been implemented. In some high- and middle-income countries, a low-level of increased risk of intussusception, a type of acute bowel obstruction, has been detected following rotavirus vaccination. However, no increased risk of intussusception was found in India, South Africa, or a network of 7 other African countries. We assessed the association between a 2-dose monovalent rotavirus vaccine (Rotarix) and intussusception in 3 early-adopter low-income Asian countries -- Afghanistan, Myanmar, and Pakistan. Children <12 months of age admitted to a sentinel surveillance hospital with Brighton level 1 intussusception were eligible for enrollment. We collected information about each child's vaccination status and used the self-controlled case series method to calculate the relative incidence of intussusception 1-7 days, 8-21 days, and 1-21 days following each dose of vaccine and derived confidence intervals with bootstrapping. Of the 585 children meeting the analytic criteria, the median age at intussusception symptom onset was 24 weeks (IQR: 19-29). Overall, 494 (84 %) children received the first Rotarix dose and 398 (68 %) received the second dose. There was no increased intussusception risk during any of the risk periods following the first (1-7 days: 1.01 (95 %CI: 0.39, 2.60); 8-21 days: 1.37 (95 %CI: 0.81, 2.32); 1-21 days: 1.28 (95 %CI: 0.78, 2.11)) or second (1-7 days: 0.81 (95 %CI: 0.42, 1.54); 8-21 days: 0.77 (95 %CI: 0.53, 1.16); 1-21 days: 0.78 (95 %CI: 0.53, 1.16)) rotavirus vaccine dose. Our findings are consistent with other data showing no increased intussusception risk with rotavirus vaccination in low-income countries and add to the growing body of evidence demonstrating safety of rotavirus vaccines.

Microparticles entrapping pneumococcal protein SP0845 show improved immunogenicity and temperature stability

Protein based vaccines are the most safe and affordable strategy to combat pneumococcal disease circumventing the limitations of conventional polysaccharide-based vaccines like serotype dependence, high cost and inability to be administered to immunocompromised. SP0845 is a highly conserved vaccine candidate shown to provide protection against heterologous strains of Streptococcus pneumoniae, the primal cause of pneumonia. However, the associated poor immunogenicity warrants the need for adjuvants and multiple doses to mount desired responses. The present study relates to improve the immunogenicity of pneumococcal protein SP0845 by use of poly lactic acid biodegradable polymer microparticles. The immunization studies showed that microparticles elicited higher antibody response compared to alum adjuvanted protein and this immunopotentiation was achieved without the use of any additional adjuvant. They were also capable of eliciting secondary antibody response upon boosting after four months. Further, the particles upon storage at 25 and 37 °C for one month were still capable of mounting an immune response equivalent to those stored in cold chain. Thus, using microparticles entrapping SP0845 for immunization not only improve the immunogenicity but also offer better temperature stability. This can greatly reduce the cost and increase access of protein-based vaccine to resource limited settings.

Characteristics of intussusception in the period of arbitrary Rotavirus vaccination

BACKGROUND

In November 2011, rotavirus (RV) vaccine was launched in Japan as a voluntary vaccination to prevent RV-associated gastroenterocolitis. We examined the characteristics of intussusception following RV vaccination in our two centers.

METHODS

We investigated intussusception patients <16 years old from January 2006 to September 2020. Patients were categorized according to the period (before [Group A] or after the introduction of arbitrary RV vaccination [Group B]). The patient characteristics and treatment of intussusception were retrospectively investigated.

RESULTS

During the study period, 560 patients (group A, n = 233; group B, n = 327) were identified. The distribution of patients who were 0-6 months old was not significantly different between the groups (group A, n = 12, 5.2%; group B, n = 18, 5.5%). Among these 18 patients in Group B, 7 were vaccinated against RV, and 10 were not. One patient was excluded due to incomplete data. On comparing patients with and without RV vaccination, the mean age at the onset of intussusception was 3.3 ± 0.4 versus 4.0 ± 0.3 months (P = 0.19), the mean interval from the onset to treatment was 7.5 ± 2.4 versus 16.0 ± 2.2 h (P = 0.03), the time of the contrast enema for treatment was 9.1 ± 3.3 versus 7.7 ± 2.8 min (P = 0.76), and the final pressure of the contrast enema was 92.5 ± 4.4 versus 92.2 ± 4.4 cmH₂ O (P = 0.97).

CONCLUSIONS

Arbitrary RV vaccination did not influence the age distribution of intussusception, and the interval from the onset to treatment was significantly shorter in the patients with RV vaccination than in those without it. Recognizing the presence of intussusception following RV vaccination enables accurate treatment.

Epidemiology of intussusception among infants in Togo, 2015-2018

Introduction

intussusception is the leading cause of bowel obstruction in infants and young children. We describe the epidemiology and diagnostic and treatment characteristics of intussusception among Togolese infants over a 4-year period.

Methods

we implemented active surveillance among infants younger than 1 year of age admitted with intussusception from 2015 to 2018 at Sylvanus Olympio Teaching Hospital and in 2018 at Campus Teaching Hospital. Brighton Collaboration Level 1 case definition criteria were used to confirm the diagnosis of intussusception.

Results

during four years, 41 cases of intussusception, with an annual range of 8 to 14 cases (median: 10) were reported; and the highest number of cases (89%) was enrolled at Sylvanus Olympio teaching hospital. Intussusception was uncommon in the first 2 months of life, peaked from 5 to 7 months old (63%), with male predominance (63%), and showed no significant seasonality. One third of cases (34%) were transferred to the sentinel surveillance site from another health facility; and the median delay in seeking care was 4 days (range: 0-11) with ≥ 48-hour delay in 59% of cases. Clinical symptoms, ultrasound and surgery were combined to diagnose intussusception in all the cases (100%). The treatment was exclusively surgical, and intestinal resection was common (28/41, 68%). A high case fatality rate (23%) was observed and the average length of hospital stay was 10 days (range: 1-23).

Conclusion

active surveillance for intussusception in Togo has highlighted exclusive use of surgical therapy; often associated to an intestinal resection with a very high case fatality rate.

Global Experience with Rotavirus Vaccines

Rotavirus is a major cause of severe pediatric diarrhea worldwide. In 2006, two live, oral rotavirus vaccines, Rotarix and RotaTeq, were licensed for use in infants and were rapidly adopted in many high- and middle-income settings where efficacy had been demonstrated in clinical trials. Following completion of additional successful trials in low-income settings, the World Health Organization (WHO) recommended rotavirus vaccination for all infants globally in 2009. In 2018, two new rotavirus vaccines, Rotasiil and Rotavac, were prequalified by WHO, further expanding global availability. As of March 2021, rotavirus vaccines have been introduced nationally in 106 countries. Since introduction, rotavirus vaccines have demonstrated effectiveness against severe disease and mortality, even among age groups not eligible for vaccination. Cross-genotypic protection has also been demonstrated, and the favorable benefit-risk profile of these vaccines continues to be confirmed via post-marketing surveillance. Ongoing research seeks to better understand reasons for the lower effectiveness observed in lower-resource settings, and to use these findings to optimize vaccine strategies worldwide.

Childhood Intussusception after Introduction of Indigenous Rotavirus Vaccine: Hospital-Based Surveillance Study from Odisha, India

OBJECTIVE

To study the epidemiology of intussusception in children < 2 y of age, postintroduction of Rotavac® (an indigenous oral rotavirus vaccine).

METHODS

A multicenter hospital-based surveillance was conducted in Odisha from February 2016 to June 2019. The cases were diagnosed according to Brighton level-1 criteria. Data were collected regarding the time of onset, signs and symptoms, radiological diagnosis, management, complications, and outcome (discharged/died).

RESULTS

One hundred and twenty children < 2 y of age were enrolled. The median age was 7 mo (M:F ratio = 2:1). The most common clinical feature was abdominal distention and blood in stool. The most common method for treatment was hydrostatic/pneumatic reduction. Median time (days) between symptom onset and admission was 2. Median (IQR) duration (days) of hospitalization was 5. Most common location of intussusceptions was ileo-colic.

CONCLUSIONS

Hydrostatic/pneumatic reduction was possible in the majority presenting ≤ 48 h of symptom onset, and those presenting > 48 h mostly required surgical reduction. Intestinal resection was required in some cases presenting on day 5 of symptom onset. Majority of cases were managed by surgical reduction in Government facility.

Epidemiology of Hospitalized Intussusception Cases from Northern States in India

OBJECTIVE

To describe epidemiology of intussusception post-introduction of the rotavirus vaccine.

METHODS

Hospital-based active surveillance system was set up in three tertiary care hospitals in Chandigarh and Haryana, India, to enroll children <2 y of age admitted with intussusception as per Brighton Collaboration Level-I criteria. The clinical characteristics, treatment modalities, seasonal trends, and outcome of the illness episodes were described.

RESULTS

A total of 224 cases were reported. Majority were males (71%) and infants (69.5%). Number of intussusception was more in summer season. Location of intussusception was ileo-colic in 85% of the cases. Nearly 54% cases were treated conservatively and 46% needed surgical intervention.

CONCLUSION

Surveillance data provided the epidemiological description of intussusception cases post-introduction of the rotavirus vaccine in northern India. This data could be used to assess the impact of vaccine and safety with a special focus on intussusception.

Intussusception after Rotavirus Vaccine Introduction in India

BACKGROUND

A three-dose, oral rotavirus vaccine (Rotavac) was introduced in the universal immunization program in India in 2016. A prelicensure trial involving 6799 infants was not large enough to detect a small increased risk of intussusception. Postmarketing surveillance data would be useful in assessing whether the risk of intussusception would be similar to the risk seen with different rotavirus vaccines used in other countries.

METHODS

We conducted a multicenter, hospital-based, active surveillance study at 27 hospitals in India. Infants meeting the Brighton level 1 criteria of radiologic or surgical confirmation of intussusception were enrolled, and rotavirus vaccination was ascertained by means of vaccination records. The relative incidence (incidence during the risk window vs. all other times) of intussusception among infants 28 to 365 days of age within risk windows of 1 to 7 days, 8 to 21 days, and 1 to 21 days after vaccination was evaluated by means of a self-controlled case-series analysis. For a subgroup of patients, a matched case-control analysis was performed, with matching for age, sex, and location.

RESULTS

From April 2016 through June 2019, a total of 970 infants with intussusception were enrolled, and 589 infants who were 28 to 365 days of age were included in the self-controlled case-series analysis. The relative incidence of intussusception after the first dose was 0.83 (95% confidence interval [CI], 0.00 to 3.00) in the 1-to-7-day risk window and 0.35 (95% CI, 0.00 to 1.09) in the 8-to-21-day risk window. Similar results were observed after the second dose (relative incidence, 0.86 [95% CI, 0.20 to 2.15] and 1.23 [95% CI, 0.60 to 2.10] in the respective risk windows) and after the third dose (relative incidence, 1.65 [95% CI, 0.82 to 2.64] and 1.08 [95% CI, 0.69 to 1.73], respectively). No increase in intussusception risk was found in the case-control analysis.

CONCLUSIONS

The rotavirus vaccine produced in India that we evaluated was not associated with intussusception in Indian infants. (Funded by the Bill and Melinda Gates Foundation and others.).

Assessment of risk of intussusception after pilot rollout of rotavirus vaccine in the Indian public health system

BACKGROUND

Pre-licensure trials of ROTAVAC® were not adequately powered to assess risk of intussusception, a rare adverse event associated with other rotavirus vaccines in some settings. We examined the risk of intussusception after ROTAVAC® vaccination among Indian infants during pilot rollout of the vaccine in the public health system in three states - Himachal Pradesh, Maharashtra and Tamil Nadu.

METHODS

Passive surveillance for intussusception was set up in 35 sentinel health facilities covering 26.3 million population in the three states under monitoring of an Interministerial-Interagency Steering Committee. Clinical and immunization data were collected by independent teams. An expert committee blinded to vaccination status, classified intussusception cases using Brighton criteria. The self-controlled case-series method was used to estimate risk of intussusception (Brighton Level 1) after ROTAVAC® vaccination.

RESULTS

151 intussusception cases were included in the analysis. The relative incidence (incidence during the risk period compared to the control period) 1-21 days after doses 1 and 2 combined was 1.56 (95% CI, 0.0-5.28) and that for three doses combined was 1.88 (95% CI, 0.76-4.30). Attributable risk 1-21 days after doses 1 and 2 combined was 0.11 (95% CI, 0.0-0.25) and that for 3 doses combined was 0.42 (95% CI, 0.0-0.70) per 100,000 doses.

CONCLUSIONS

No increased risk of intussusception within 21 days of receipt of the first two doses combined or all 3 doses combined of ROTAVAC® was detected.

Intussusception in children aged under two years in India: Retrospective surveillance at nineteen tertiary care hospitals

Objective

Intussusception has been linked with rotavirus vaccine (RVV) as a rare adverse reaction. In view of limited background data on intussusception in India and in preparation for RVV introduction, a surveillance network was established to document the epidemiology of intussusception cases in Indian children.

Methods

Intussusception in children 2–23 months were documented at 19 nationally representative sentinel hospitals through a retrospective surveillance for 69 months (July 2010 to March 2016). For each case clinical, hospital course, treatment and outcome data were collected.

Results

Among the 1588 intussusception cases, 54.5% were from South India and 66.3% were boys. The median age was 8 months (IQR 6, 12) with 34.6% aged 2–6 months. Seasonal variation with higher cases were documented during March-June period. The most common symptoms and signs were vomiting (63.4%), bloody stool (49.1%), abdominal pain (46.9%) and excessive crying (42.8%). The classical triad (vomiting, abdominal pain, and blood in stools) was observed in 25.6% cases. 96.4% cases were diagnosed by ultrasound with ileocolic location as the commonest (85.3%). Management was done by reduction (50.8%) and surgery (41.1%) and only 1% of the patients’ died. 91.1% cases met Brighton criteria level 1 and 3.3% Level 2. Between 2010 and 2015, the case load and case ratio increased across all regions.

Conclusion

Intussusception cases have occurred in children across all parts of the country, with low case fatality in the settings studied. The progressive rise cases could indicate an increasing awareness and availability of diagnostic facilities.

Profit considerations in vaccine safety-related events in China

Objectives: China has made remarkable achievements in the field of immunization. However, several widespread vaccine safety-related events have recently received worldwide attention and reflect flaws in vaccine management. This study aimed to summarize vaccine safety-related events between 1985 and 2018 in China and analyze the profit motives of these events.Methods. Literature and media reviews were conducted to discover vaccine safety-related events. We developed a conceptual model with profit-related variables, and using information available from each event, we identified which profit-related variable was implicated, and how it related to the pursuit of higher profits.Results: A total of 39 vaccine safety-related events were found in vaccine production, procurement, transportation, and daily management, along with adverse events following immunization (AEFIs). Overall, 90% (35/39) of the events could be classified as profit-driven. The motives of most events could be tied to one or more reasons, including decreasing costs among vaccine producers (67%, 26/39), reducing actual procurement price (67%, 26/39), and reducing costs of transportation and/or cold chain (24/39, 62%).Conclusions: In order to deal with vaccine-related challenges, a more restrictive supervision system on vaccine production and more emergency preparedness, including health and risk communication strategies, for vaccine safety should be implemented.

Characteristics of intussusception among children in Korea: a nationwide epidemiological study

Background

Intussusception is a gastrointestinal condition in which early treatment is critical. Although its epidemiology and comorbidities have been studied, few studies have included the entire pediatric population of a country. Therefore, we aimed to analyze the epidemiologic features of pediatric intussusception patients and identify comorbidities associated with intussusception in South Korea, using the public health database.

Methods

We analyzed the data of children below 18 years of age, from the national database of South Korea, who were diagnosed with intussusception and managed such as air reduction or surgical methods from 2008 to 2016. Patients were categorized into six groups based on the comorbid diseases. Patients with structural lesion in gastrointestinal tract were divided diagnosis or diagnosis code.

Results

The number of patients diagnosed with intussusception were 25,023 (16,024 males, 64.0%). Of them, the highest percentage was patients aged between 2 and 36 months (20,703; 82.7%). The incidence per 100,000 individuals aged up to 2 years was 196.7. The number of males were 16,024 (64.0%) and were almost twice the number of 8999 (36.0%) female patients. The maximum number of cases (n = 2517; 10.1%) were seen in September, followed by July (n = 2469; 9.9%). In February, the number of cases was lowest at 1448 (5.8%) patients (P < 0.001). The number of patients with structural lesions of the gastrointestinal tract that could lead to intussusception was 1207 (4.8%), while patients with acute gastrointestinal infectious disease were 4541 (18.1%). Among the structural lesions of the gastrointestinal tract that could be the leading cause of intussusception, lymphadenopathy was the most common, seen in 462 (56.6%) patients and an appendix-related condition was seen in 260 (31.9%) patients. Infectious diseases were more common in the younger children, while systemic diseases were more common in the older.

Conclusion

We confirmed that pediatric intussusception in South Korea shows a seasonal tendency, which is age-dependent and is associated with an exposure to infectious agents. Some infectious pathogens and underlying diseases might play an important role in the pathophysiology of intussusception.

The Anti-Rotaviral Activity of Low Molecular Weight and Non-Proteinaceous Substance from Bifidobacterium longum BORI Cell Extract

Rotavirus infection is the most common diarrheal disease worldwide in children under five years of age, and it often results in death. In recent years, research on the relationship between rotavirus and probiotics has shown that probiotics are effective against diarrhea. A clinical trial has reported that Bifidobacterium longum BORI reduced diarrhea induced by rotavirus. The present work investigated the anti-rotaviral effect of B. longum BORI by cytopathic effect observation and real time cell analyses. Our study found that B. longum BORI showed strong anti-rotaviral effect when incubated with MA104 cells prior to viral infection, suggesting that the probiotic does in fact interfere with the interaction of viruses and host cells. It is believed that the efficacy is due to low-molecular weight and non-protein components derived from B. longum BORI. This discovery can help broaden the industrial application of B. longum BORI, which has been proven to be a safe and effective probiotic.

Lack of immune interference between inactivated polio vaccine and inactivated rotavirus vaccine co-administered by intramuscular injection in two animal species

A parenteral inactivated rotavirus vaccine (IRV) in development could address three problems with current live oral rotavirus vaccines (ORV): their lower efficacy in low and middle-income countries (LMICs), lingering concerns about their association with intussusception, and their requirement for a separate supply chain with large volume cold storage. Adding a new parenteral IRV to the current schedule of childhood immunizations would be more acceptable if it could be combined with another injectable vaccine such as inactivated polio vaccine (IPV). Current plans for polio eradication call for phasing out oral polio vaccine (OPV) and transitioning to IPV, initially in LMICs as a single dose booster after two doses of OPV and ultimately as a two dose schedule. Today in many LMICs, IPV is administered as a standalone vaccine, which involves a separate cold chain and is relatively costly. We therefore tested in two animal models formulations of IPV with IRV to determine whether co-administration might interfere with the immune response to each product and spare antigen dose for both vaccines. Our results demonstrate that IRV when adjuvanted with alum and administered alone or in combination with IPV did not impair the immune responses to either rotavirus or poliovirus serotypes 1, 2 and 3. Similarly, IPV when formulated and administered alone or together with IRV induced comparable levels of neutralizing antibody to poliovirus type 1, 2 and 3. Furthermore, comparable antibody titers were observed in animals vaccinated with low, middle or high dose of IPV or IRV in combination. This dose sparing and the lack of interference between IPV and IRV administered together represent another step to support the further development of this novel combination vaccine for children.

Rotavirus VP6 protein mucosally delivered by cell wall-derived particles from Lactococcus lactis induces protection against infection in a murine model

Rotaviruses are the primary cause of acute gastroenteritis in children worldwide. Although the implementation of live attenuated vaccines has reduced the number of rotavirus-associated deaths, variance in their effectiveness has been reported in different countries. This fact, among other concerns, leads to continuous efforts for the development of new generation of vaccines against rotavirus.In this work, we describe the obtention of cell wall-derived particles from a recombinant Lactococcus lactis expressing a cell wall-anchored version of the rotavirus VP6 protein. After confirming by SDS-PAGE, Western blot, flow cytometry and electronic immunomicroscopy that these particles were carrying the VP6 protein, their immunogenic potential was evaluated in adult BALB/c mice. For that, mucosal immunizations (oral or intranasal), with or without the dmLT [(double mutant Escherichia coli heat labile toxin LT(R192G/L211A)] adjuvant were performed. The results showed that these cell wall-derived particles were able to generate anti-rotavirus IgG and IgA antibodies only when administered intranasally, whether the adjuvant was present or not. However, the presence of dmLT was necessary to confer protection against rotavirus infection, which was evidenced by a 79.5 percent viral shedding reduction.In summary, this work describes the production of cell wall-derived particles which were able to induce a protective immune response after intranasal immunization. Further studies are needed to characterize the immune response elicited by these particles as well as to determine their potential as an alternative to the use of live L. lactis for mucosal antigen delivery.

Intussusception Rate Among Under-Five-Children Before Introduction of Rotavirus Vaccine in North India

BACKGROUND

Baseline data on intussusception are needed to compare the intussusception rates following introduction of rotavirus vaccine.

METHODS

A hospital-based bidirectional surveillance (retrospective from 2009 to 2012; and prospective from 2013 to 2015) was set up in a tertiary care hospital in Chandigarh, India, to enrol children <5 years of age admitted with intussusception as per Brighton's classification, to estimate the hospital admission rate. Incidence of intussusception among infants and children <5 years of age was also estimated.

RESULTS

A total of 277 intussusception cases (96 retrospective; 181 prospective) were reported. Majority of cases were males (69.7%) and infants (72%). Median age at diagnosis was 10 months (interquartile range 6-12 months). Nearly 62% cases were treated surgically and 33% radiologically. Incidence was estimated to be 20/100 000 infants, and 5/100 000 children <5 years of age per year, in Chandigarh.

CONCLUSION

Intussusception surveillance system provided background hospital admission and incidence rate before rotavirus vaccine introduction in North India.

Rotavirus Vaccines: Effectiveness, Safety, and Future Directions

Rotavirus is the leading cause of diarrheal death among children < 5 years old worldwide, estimated to have caused ~ 215,000 deaths in 2013. Prior to rotavirus vaccine implementation, > 65% of children had at least one rotavirus diarrhea illness by 5 years of age and rotavirus accounted for > 40% of all-cause diarrhea hospitalizations globally. Two live, oral rotavirus vaccines have been implemented nationally in > 100 countries since 2006 and their use has substantially reduced the burden of severe diarrheal illness in all settings. Vaccine efficacy and effectiveness estimates suggest there is a gradient in vaccine performance between low child-mortality countries (> 90%) and medium and high child-mortality countries (57-75%). Additionally, an increased risk of intussusception (~ 1-6 per 100,000 vaccinated infants) following vaccination has been documented in some countries, but this is outweighed by the large benefits of vaccination. Two additional live, oral rotavirus vaccines were recently licensed and these have improved on some programmatic limitations of earlier vaccines, such as heat stability, cost, and cold-chain footprint. Non-replicating rotavirus vaccines that are parenterally administered are in clinical testing, and these have the potential to reduce the performance differential and safety concerns associated with live oral rotavirus vaccines.

Safety of a heat-stable rotavirus vaccine among children in Niger: Data from a phase 3, randomized, double-blind, placebo-controlled trial

BACKGROUND

Rotavirus remains a major cause of diarrhea among children under 5 years of age. The efficacy of RotaSIIL, a pentavalent rotavirus vaccine, was shown in an event-driven trial in Niger. We describe the two-year safety follow-up of this trial.

METHODS

Follow-up of safety outcomes began upon administration of the first dose of RotaSIIL or placebo. Adverse events were followed until 28 days after the third dose, and serious adverse events were followed until 2 years of age. Suspected cases of intussusception were evaluated at first point of contact and then referred to hospital for surgical evaluation. Causes of death were obtained by chart review and verbal autopsy. Passive surveillance was carried out in health centers. Community health workers carried out active surveillance in villages. Between-group differences were evaluated using the chi-squared test and Fisher's exact test.

RESULTS

A total of 4092 children were randomized, and 4086 received at least one dose of RotaSIIL or placebo, constituting the intention-to-treat population, who accrued a total of 7385 child-years of follow-up time. At two years of follow-up, 58 (2.8%) participants who received RotaSIIL and 49 (2.4%) participants who received placebo had died (p = 0.38). Most deaths were due to infectious causes common to the study area. One participant had confirmed intussusception, 542 days after receiving the third dose of RotaSIIL. A total of 395 (19.3%) participants receiving RotaSIIL and 419 (20.5%) participants receiving placebo experienced any serious adverse event (p = 0.36). Most serious adverse events were hospitalizations due to infection (malaria, lower respiratory tract infection and gastroenteritis) or marasmus. Overall, 1474 (72.1%) participants receiving RotaSIIL and 1456 (71.1%) participants receiving placebo had at least one adverse event (p = 0.49) in the follow-up period.

CONCLUSIONS

At two years of follow-up, RotaSIIL was found to be safe.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02145000.

Evaluation of the Intussusception Risk after Pentavalent Rotavirus Vaccination in Finnish Infants

BACKGROUND

An association between rotavirus immunisation and intussusception (IS) has been suggested with present rotavirus vaccines in post-licensure studies. In Finland, rotavirus vaccination programme was implemented in September 2009 using a 2, 3, and 5 months schedule with the pentavalent rotavirus vaccine. By the end of 2013, it is estimated that 719 000 rotavirus vaccine doses have been given in the national programme of which 240 000 were first doses. Nationwide register allows us to evaluate the association between rotavirus vaccination and IS.

METHODS AND MATERIALS

Cases of IS diagnosed during 1999-2013 were identified from National Hospital Discharge Register. All cases under 250 days of age diagnosed during 2009-2013 were confirmed by reviewing medical charts. Self-controlled case-series method was used to assess the risk of IS during 1-21 days compared to 22-42 days post vaccination.

FINDINGS

In register data the relative incidence of IS at 2 months of age between the post and pre vaccination era was 9.1 (95%CI 2.0-84.3). We identified 22 verified cases with date of admission less than 43 days after any of the three rotavirus vaccine doses. The incidence of IS in the risk period after the 1st dose relative to the control period was 2.0 (95% CI 0.5-8.4; p = 0.34.) Number of excess IS cases per 100 000 first vaccine doses was therefore estimated to be 1.04 (95% CI 0.0-2.5), i.e. one additional IS case per 96 000 first doses of rotavirus vaccine (95% CI 54 600 to ∞). There was no risk detected after 2nd and 3rd doses.

CONCLUSION

The finding is in line with the recent published estimates. The benefits of rotavirus immunisation programme outweigh possible small risks of intussusception.

Hospital-based surveillance of intussusception among infants

OBJECTIVE

Intussusception surveillance was initiated after the nationwide introduction of live attenuated monovalent rotavirus vaccine (RV1). The objective is to assess the epidemiology of intussusception and compare the number of cases before and after the introduction of rotavirus vaccine.

METHODS

Cases of intussusception occurring between March 2006 and January 2008 were identified through a prospective enhanced passive surveillance system established in sentinel state hospitals. Retrospective review of medical records was used to identify cases, which occurred in sentinel hospitals between January 2001 and February 2006.

RESULTS

From 2001 to 2008, 331 intussusception cases were identified, 59.5% were male, with peak incidence among those 18-24 weeks of age. Overall <10% of cases were among infants 6-14 weeks of age (when the first dose of RV1 is administered). The most frequently observed signs or symptoms of intussusception included vomiting (89.4%), bloody stool (75.5%), and abdominal distention (71.8%). A majority (92.1%) of the case-patients required surgery for treatment; 31.8% of those who underwent surgery required bowel resection, and 13 (3.9%) died. Among the 21 hospitals that reported cases throughout the entire surveillance period (2001-2008), the number of intussusception events during 2007 (n=26) and 2008 (n=19) was not greater than the average annual number (n=31, range 24-42) during baseline years 2001-2005.

CONCLUSIONS

Although this analysis did not identify an increase in intussusception cases during the two years after RV1 introduction, these results support the need for special epidemiologic methods to assess the potential link between rotavirus vaccine and this very rare adverse event.

Noninterference of Rotavirus Vaccine With Measles-Rubella Vaccine at 9 Months of Age and Improvements in Antirotavirus Immunity: A Randomized Trial

Background. The burden of rotavirus morbidity and mortality is high in children aged <5 years in developing countries, and evaluations indicate waning protection from rotavirus immunization in the second year. An additional dose of rotavirus vaccine may enhance the immune response and lengthen the period of protection against disease, but coadministration of this dose should not interfere with immune responses to concurrently given vaccines.

Methods. A total of 480 9-month-old participants from Matlab, Bangladesh, were enrolled in a study with a primary objective to establish noninferiority of concomitant administration of measles-rubella vaccine (MR) and a third dose of human rotavirus vaccine (HRV; MR + HRV), compared with MR given alone. Secondary objectives included noninferiority of rubella antibody seroconversion and evaluating rotavirus IgA/IgG seroresponses in MR + HRV recipients.

Results. Two months after vaccination, 75.3% and 74.3% of MR + HRV and MR recipients, respectively, had seroprotective levels of measles virus antibodies; 100.0% and 99.6%, respectively, showed anti–rubella virus immunoglobulin G (IgG) seroprotection. In the MR + HRV group, antirotavirus immunoglobulin A and IgG seropositivity frequencies before vaccination (52.7% and 66.3%, respectively) increased to 69.6% and 88.3% after vaccination.

Conclusions. Vaccine-induced measles and rubella antibody responses are not negatively affected by concomitant administration of HRV. The HRV dose increases antirotavirus serum antibody titers and the proportion of infants with detectable antirotavirus antibody.

Clinical Trials Registration. NCT01700621.

Immunogenicity and efficacy in mice of an adenovirus-based bicistronic rotavirus vaccine expressing NSP4 and VP7

NSP4 and VP7 are important functional proteins of rotavirus. Proper combination of viral gene expression is favorable to improving the protection effect of subunit vaccine. In the present study, We evaluated the immunogenicity and efficacy of the bicistronic recombinant adenovirus (rAd-NSP4-VP7) and two single-gene expressing adenoviruses (rAd-NSP4, rAd-VP7). The three adenovirus vaccines were used to immunize mice by intramuscular or intranasal administration. The data showed significant increases in serum antibodies, T lymphocyte subpopulations proliferation, and cytokine secretions of splenocyte in all immunized groups. However, the serum IgA and neutralizing antibody levels of the rAd-NSP4-VP7 or rAd-VP7 groups were significantly higher than those of the rAd-NSP4, while the splenocyte numbers of IFN-γ secretion in the rAd-NSP4-VP7 or rAd-NSP4 groups was greater than that of the rAd-VP7. Furthermore, the efficacy evaluation in a suckling mice model indicated that only rAd-NSP4-VP7 conferred significant protection against rotavirus shedding challenge. These results suggest that the co-expression of NSP4 and VP7 in an adenovirus vector induce both humoral and cell-mediated immune responses efficiently, and provide potential efficacy for protection against rotavirus disease. It is possible to represent an efficacious subunits vaccine strategy for control of rotavirus infection and transmission.

Catching-up with pentavalent vaccine: Exploring reasons behind lower rotavirus vaccine coverage in El Salvador

Rotavirus vaccine was introduced in El Salvador in 2006 and is recommended to be given concomitantly with DTP–HepB–Haemophilus influenzae type b (pentavalent) vaccine at ages 2 months (upper age limit 15 weeks) and 4 months (upper age limit 8 months) of age. However, rotavirus vaccination coverage continues to lag behind that of pentavalent vaccine, even in years when national rotavirus vaccine stock-outs have not occurred. We analyzed factors associated with receipt of oral rotavirus vaccine among children who received at least 2 doses of pentavalent vaccine in a stratified cluster survey of children aged 24–59 months conducted in El Salvador in 2011. Vaccine doses included were documented on vaccination cards (94.4%) or in health facility records (5.6%). Logistic regression and survival analysis were used to assess factors associated with vaccination status and age at vaccination. Receipt of pentavalent vaccine by age 15 weeks was associated with rotavirus vaccination (OR: 5.1; 95% CI 2.7, 9.4), and receipt of the second pentavalent dose by age 32 weeks was associated with receipt of two rotavirus vaccine doses (OR: 5.0; 95% CI 2.1–12.3). Timely coverage with the first pentavalent vaccine dose was 88.2% in the 2007 cohort and 91.1% in the 2008 cohort (p = 0.04). Children born in 2009, when a four-month national rotavirus vaccine stock-out occurred, had an older median age of receipt of rotavirus vaccine and were less likely to receive rotavirus on the same date as the same dose of pentavalent vaccine than children born in 2007 and 2008. Upper age limit recommendations for rotavirus vaccine administration contributed to suboptimal vaccination coverage. Survey data suggest that late rotavirus vaccination and co-administration with later doses of pentavalent vaccine among children born in 2009 helped increase rotavirus vaccine coverage following shortages.

Retrospective surveillance for intussusception in children aged less than five years at two tertiary care centers in India

BACKGROUND

A rotavirus vaccine could soon become part of India's national immunization program. However the occurrence of intussusception due to rotavirus vaccine is a potential safety concern. This surveillance aimed at the collection of baseline data on childhood intussusception which would facilitate the monitoring of intussusception cases after the introduction of rotavirus vaccines.

METHODS

We retrospectively reviewed medical records of confirmed intussusception cases in children under the age of five, treated during 2007-2012 at two tertiary care hospitals attached to medical schools in India. Demographic, clinical, diagnostic and treatment practices data were obtained from hospital records.

RESULTS

Over a five to six year observation period, we identified 187 confirmed cases of intussusception, of which 75% were males. The median age of intussusception was 8 months, and we observed a possible trend in the distribution of cases with the highest number of cases being reported in the month of April and lowest in the month of October. The most common diagnostic methods used were ultrasonography and abdominal radiography with most cases being treated surgically (71%). The median length of hospital stay was 8 days (range 1-40) and mean was 10.2 days. Records of any fatality due to intussusception were not found during the review of the records.

CONCLUSIONS

This analysis provides an estimate of the baseline data of childhood intussusception prior to the introduction of the rotavirus vaccination as a part of routine immunization in India. A prospective surveillance system using a standardized case definition is needed in order to better examine the incidence of intussusception in developing countries.

Intussusception in southern India: comparison of retrospective analysis and active surveillance

Surveillance for intussusception is a post marketing requirement for rotavirus vaccines following observation of a small increased risk of intussusception after rotavirus vaccination in some global settings. This study presents the clinical presentation and outcomes of children who presented with intussusception at a large tertiary care facility directly (non-surveillance) as retrospective analysis of a period where rotavirus vaccine was not in routine use, or as part of active surveillance in a phase III oral rotavirus vaccine trial. Hospital records of children under 2 years of age treated for intussusception between 1 January 2010 and 31 August 2013 at the Christian Medical College Hospital, Vellore, India, were reviewed. Sixty-one cases of intussusception in children under two years of age presented at the hospital. An additional 16 cases of ultrasound diagnosed intussusception were identified through the active surveillance of a cohort of 1500 children participating in a rotavirus phase III trial in the same period. In the nonsurveillance group, median age at presentation was 214 days (IQR 153-321) with 52 events (85.3%) occurring in the first year of life. Cases were seen year-round with no definitive evidence of seasonality. Thirty-one (50.8%) intussusceptions required surgical reduction, 26 (42.6%) had pneumatic reduction and 2 (3.3%) barium enema reduction. Two intussusceptions (3.3%) resolved spontaneously. There were no deaths, all children were discharged after recovery. Active surveillance identified 16 children with a median age at event of 375 days (IQR 248-574). Nine (56%) children had small bowel or transient intussusception that resolved spontaneously. Seven intussusceptions were reduced radiologically; none required surgery. In summary, there were significant differences between presentation and outcomes in cases of intussusception identified by passive and active surveillance, likely related to enhanced and early detection of intussusception through active monitoring in the trial. The WHO recommendation of sentinel hospital based surveillance for post-marketing surveillance after rotavirus vaccine introduction is likely to a better approach than active surveillance.

Inactivated Viral Vaccines

Inactivated vaccines have been used for over a century to induce protection against viral pathogens. This established approach of vaccine production is relatively straightforward to achieve and there is an augmented safety profile as compared to their live counterparts. Today, there are six viral pathogens for which licensed inactivated vaccines are available with many more in development. Here, we describe the principles of viral inactivation and the application of these principles to vaccine development. Specifically emphasized are the manufacturing procedure and the accompanying assays, of which assays used for monitoring the inactivation process and preservation of neutralizing epitopes, are pivotal. Novel inactivated vaccines in development and the hurdles they face for licensure are also discussed as well as the (dis)advantages of inactivation over the other vaccine production methodologies.

Intussusception after monovalent human rotavirus vaccine in Australia: severity and comparison of using healthcare database records versus case confirmation to assess risk

BACKGROUND

Surveillance for intussusception (IS) has been recommended in countries using rotavirus vaccine, but can be resource intensive. There is little data about the relative severity of rotavirus vaccine-associated IS compared with other IS cases. We collected detailed clinical data on all cases to evaluate the validity of ICD coding for IS in routinely collected data and case severity.

METHODS

Hospitalizations and emergency department presentations coded as IS in infants aged <12 months from July 1, 2007, to June 30, 2010, were classified using Brighton criteria by case note review. We used self-controlled case series analysis to estimate IS risk after vaccination for all and only Brighton level 1 cases.

RESULTS

Of 179 unique episodes coded as IS, 110 (61%) met Brighton level 1 criteria; self-controlled case series analysis found a relative incidence of IS in days 1-7 after the first dose of RV1 of 11.1 (95% confidence interval: 2.6-48.0). When all coded episodes of IS were included, relative incidence was 4.0 (95% confidence interval: 1.3-12.7). The proportion of Brighton 1 cases requiring surgery was 39% for those within 21 days of vaccine receipt and 34% for others (P = 0.67).

CONCLUSIONS

Using ICD-coded cases without individual confirmation yielded a lower point estimate of risk for IS post rotavirus vaccination; however, the risk remained statistically compatible with that for chart confirmed cases only. Analysis using healthcare databases to evaluate risk of IS if conducted without case confirmation may be insufficient to confirm a low-level risk. IS episodes after vaccination were not more severe.

Rotavirus vaccination in Europe: drivers and barriers

Rotavirus gastroenteritis is a vaccine-preventable disease that confers a high medical and economic burden in more developed countries and can be fatal in less developed countries. Two vaccines with high efficacy and good safety profiles were approved and made available in Europe in 2006. We present an overview of the status of rotavirus vaccination in Europe. We discuss the drivers (including high effectiveness and effect of universal rotavirus vaccination) and barriers (including low awareness of disease burden, perception of unfavourable cost-effectiveness, and potential safety concerns) to the implementation of universal rotavirus vaccination in Europe. By February, 2014, national universal rotavirus vaccination had been implemented in Belgium, Luxembourg, Austria, Finland, Greece, Luxembourg, Norway, and the UK. Four other German states have issued recommendations and reimbursement is provided by sickness funds. Other countries were at various stages of recommending or implementing universal rotavirus vaccination.

Incidence and Epidemiology of Intussusception among Infants in Ho Chi Minh City, Vietnam

OBJECTIVE

To evaluate rates of intussusception hospitalization among infants in Vietnam before the introduction of rotavirus vaccine.

STUDY DESIGN

Between 2009 and 2011, we identified intussusception hospitalizations among infants using the International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Clinical Modification code K56.1 at 2 large pediatric hospitals in Ho Chi Minh City, Vietnam that treat most of the intussusception cases in the city. We reviewed all medical records to confirm a Brighton level 1 case definition for intussusception.

RESULTS

We identified a total of 869 intussusception cases in Ho Chi Minh City during the 3-year study period, for an annual rate of 296 per 100,000 infants. The mean age of intussusception was ∼ 37 weeks (8.6 months), with <2% of the cases occurring before age 15 weeks. Cases of intussusception were observed year-round in these hospitals with no evident seasonal pattern. Ultrasonography was used to diagnose most cases (97%), and reduction was performed by air enema in >95% of the cases, with only 1% of cases at 1 hospital and 5% at the other hospital requiring surgical intervention. Ultrasound diagnosis was confirmed by an independent radiologist in 94% of a randomly selected group of intussusception cases at 1 of the 2 hospitals. No mortality was reported.

CONCLUSION

Vietnam has a substantially higher rate of intussusception in children aged >15 weeks compared with most other regions of the world. Most of our cases were diagnosed by ultrasound, and only a small proportion required surgical intervention with no fatalities, suggesting that the higher rates may be related in part to better and earlier detection of intussusception.

The human rotavirus vaccine Rotarix™ in infants: an integrated analysis of safety and reactogenicity

An integrated analysis of safety and reactogenicity data was undertaken for 28 randomized, placebo-controlled, double-blind Phase II and III trials (DBRCTs) of the oral live-attenuated human rotavirus vaccine, Rotarix™ (GlaxoSmithKline Vaccines). Healthy infants aged 6-20 wk received 2 or 3 doses of vaccine (n=56562) or placebo (n=45512) at 4- to 8-wk intervals. Solicited adverse events (AEs) were recorded for 8 d after each dose of vaccine or placebo. Unsolicited AEs, serious AEs (SAEs), and deaths were evaluated over 31-d post-vaccination follow-up periods. 95% confidence intervals (CIs) for the relative risk (RR) across studies excluding "1.0" signified potential imbalances between the 2 groups. The incidence of each solicited AE of any or Grade 3 severity was similar between groups. The incidence of all unsolicited AEs of any (RR=0.99 [95% CI: 0.94-1.04]; P=0.72) or Grade 3 severity (RR=0.91 [95% CI: 0.77-1.08]; P=0.31) was similar between groups. A significantly higher proportion of SAEs were reported in the placebo group compared with the vaccine group (RR=0.9 [95% CI: 0.82-0.98]; P=0.01). The incidence of death was low and similar between the 2 groups (0.13% in the vaccine group and 0.11% in the placebo group; RR=1.14 [95% CI: 0.78-1.68]; P=0.54). Very few cases of intussusception were reported (11 and 7 in the vaccine and placebo groups, respectively; RR=1.39 [95% CI: 0.49-4.27]; P=0.66). In conclusion, results of this analysis of DBRCTs show that the human rotavirus vaccine Rotarix™ has a reactogenicity and safety profile similar to placebo.

Childhood intussusception: a literature review

Background

Postlicensure data has identified a causal link between rotavirus vaccines and intussusception in some settings. As rotavirus vaccines are introduced globally, monitoring intussusception will be crucial for ensuring safety of the vaccine programs.

Methods

To obtain updated information on background rates and clinical management of intussusception, we reviewed studies of intussusception in children <18 years of age published since 2002. We assessed the incidence of intussusception by month of life among children <1 year of age, seasonality, method of diagnosis, treatment, and case-fatality.

Findings

We identified 82 studies from North America, Asia, Europe, Oceania, Africa, Eastern Mediterranean, and Central & South America that reported a total of 44,454 intussusception events. The mean incidence of intussusception was 74 per 100,000 (range: 9–328) among children <1 year of age, with peak incidence among infants 5–7 months of age. No seasonal patterns were observed. A radiographic modality was used to diagnose intussusception in over 95% of the cases in all regions except Africa where clinical findings or surgery were used in 65% of the cases. Surgical rates were substantially higher in Africa (77%) and Central and South America (86%) compared to other regions (13–29%). Case-fatality also was higher in Africa (9%) compared to other regions (<1%). The primary limitation of this review relates to the heterogeneity in intussusception surveillance across different regions.

Conclusion

This review of the intussusception literature from the past decade provides pertinent information that should facilitate implementation of intussusception surveillance for monitoring the postlicensure safety of rotavirus vaccines.

Paediatric active enhanced disease surveillance: a new surveillance system for Australia

AIM

The Paediatric Active Enhanced Disease Surveillance (PAEDS) is described. PAEDS is active in four tertiary children's hospitals in four states of Australia and aims to address gaps in surveillance for severe vaccine-preventable diseases and adverse events following immunisation.

METHODS

From August 2007 to December 2010, surveillance nurses actively identified and recruited children admitted with: acute flaccid paralysis, varicella infection, intussusception, seizures in infants and pandemic influenza (June-October 2009). Details of presentation, medical and immunisation history, outcome and laboratory results were collected. Completeness of ascertainment was estimated through audits of International Classification of Diseases 10th edition-coded medical records where possible.

RESULTS

Seven hundred thirty-three cases matching case definition criteria for the four conditions were recruited. In addition, 601 cases of influenza were recruited during the 2009 pandemic. PAEDS enhanced acute flaccid paralysis surveillance by the Australian Paediatric Surveillance Unit; the World Health Organization surveillance target was met when Australian Paediatric Surveillance Unit and PAEDS cases were combined. Among 133 children hospitalised for varicella, only 16 were vaccinated; samples of vesicle scrapings were collected in 57% for genotyping. Of 122 infants presenting with seizures, only six (12%) had received a vaccine in the last 7 days. Intussusception was more frequent among infants receiving their first dose of either of the rotavirus vaccines. Results informed policy and education for parents and health professionals. Preliminary audits of medical records suggest excellent ascertainment through PAEDS.

CONCLUSIONS

PAEDS provides important, previously unavailable data to inform public health policy, clinical practice and community confidence. It has potential to respond quickly during outbreaks and epidemics.

Establishing pharmacovigilance programs in resource-limited settings: the example of treating malaria

The unprecedented levels of political, technical and financial support for improved malaria control, and particularly for changes in the malaria treatment policy, have heralded a renewed appreciation of the role of pharmacovigilance, its relationship with other areas of public health and the development of novel approaches to addressing the pharmacovigilance priorities in malaria-endemic countries. In order to become a valuable public health activity in these resource-limited settings, pharmacovigilance needs to be viewed within its broadest definition of detecting, understanding and preventing adverse drug reactions and drug-related problems. Pharmacovigilance in resource-limited settings provides an opportunity to identify and address health system failures that significantly impact on patient morbidity and mortality, particularly those that are drug related. Countries need to establish a national strategy that identifies realistic and relevant objectives that meet the most pressing pharmacovigilance needs, taking into consideration the conditions under which these systems are likely to develop.

Retrospective hospital based surveillance of intussusception in children in a sentinel paediatric hospital: benefits and pitfalls for use in post-marketing surveillance of rotavirus vaccines

Evaluation of the safety of rotavirus vaccines, particularly with respect to the risk of intussusception, is recommended for countries planning to introduce rotavirus vaccines into the National Immunisation Program. However, as prospective studies are costly, require time to conduct and may be difficult to perform in some settings, retrospective hospital based surveillance at sentinel sites has been suggested as an option for surveillance for intussusception following introduction of rotavirus vaccines.

OBJECTIVE

To assess the value of retrospective hospital based surveillance to describe clinical and epidemiological features of intussusception in children aged <24 months and to investigate any temporal association between receipt of a rotavirus vaccine and intussusception.

METHODS

A retrospective chart review of all patients diagnosed with intussusception at Royal Children's Hospital, Melbourne, Australia over an 8-year period including before and after rotavirus vaccine introduction into the National Immunisation Program, was conducted using patients identified by a medical record database (ICD-10-CM 56.1). Patient profile, clinical presentation, treatment and outcome were analysed along with records of immunisation status obtained using the Australian Childhood Immunisation Register.

RESULTS

A 9% misclassification rate of discharge diagnosis of intussusception was identified on critical chart review. The incidence rate of intussusception at the Royal Children's Hospital over the study period was 1.91 per 10,000 infants <24 months (95% CI 1.65-2.20). Intestinal resection was required in 6.5% of infants (95% CI 3.6%, 11.0%). Intussusception occurred within 30 days after vaccination in 2 of 27 patients who had received at least 1 dose of a rotavirus vaccine.

CONCLUSIONS

Valuable data on the incidence, clinical presentation and treatment outcomes of intussusception can be obtained from data retrieved from hospital medical records in a sentinel paediatric hospital using standardised methodology. However, there are methodological limitations and the quality of the data is highly dependent on the accuracy and completeness of the patient information recorded, the system of coding and record retrieval.

Workshop on intussusception in African countries--meeting report

Rotavirus causes approximately 450,000 deaths annually among children less than 5 years of age worldwide, almost half of which occur in Africa. After the recent completion of successful trials of 2 new rotavirus vaccines, the World Health Organization has recommended these vaccines for all children worldwide. Because a previous rotavirus vaccine, Rotashield(®), was associated with intussusception, a form of intestinal obstruction among infants, the current rotavirus vaccines were tested in large clinical trials and found to be safe. However, due to the past Rotashield(®) experience, post licensure monitoring of intussusception is considered to be crucial after the introduction of future oral rotavirus vaccines. Thus, in planning for future introductions of rotavirus vaccine in Africa, a workshop of experts working on intussusception was convened by the World Health Organization in May 2004 in association with the Pan-African Association of Paediatric Surgeons (PAPSA) in Malawi. In brief, delegates from ten countries presented data from retrospective record reviews of intussusception events from 1993 to 2003 at selected hospitals in their respective countries. This review showed that age of intussusception onset during infancy varies markedly with peak prevalence between 4 and 6 months of life. Diagnostic modality (e.g., contrast enema, ultrasound) was employed in <20% of the events; nearly 70% of the intussusception events were diagnosed at the time of surgery. Overall, case-fatality was high, ~13%, in these African countries. The findings of this meeting highlight the challenges in implementing surveillance for intussusception after rotavirus vaccine introduction in Africa. The deliberations identified some concrete steps necessary to establish active surveillance at sentinel sites in African countries. This is becoming more urgent now that many countries are expressing interest in introducing rotavirus vaccines.

Postmarketing surveillance of intussusception following mass introduction of the attenuated human rotavirus vaccine in Mexico

BACKGROUND

Mexico initiated mass vaccination with the attenuated human rotavirus vaccine (Rotarix) in 2006. This postlicensure study aimed to assess any potential temporal association between vaccination and intussusception in Mexican infants.

METHODS

Prospective, active surveillance for intussusception among infants aged less than 1 year was conducted in 221 hospitals across Mexico from the Mexican Institute of Social Security between January 2008 and October 2010. The temporal association between vaccination and intussusception was assessed by self-controlled case-series analysis.

RESULTS

Of the 753 episodes of intussusception reported in 750 infants, 701 were in vaccinated infants (34.5% post-dose 1, 65.5% post-dose 2). The relative incidence of intussusception within 31 days of vaccination was 1.75 (95.5% confidence interval [CI]: 1.24-2.48; P=0.001) post-dose 1 and 1.06 (95.5% CI: 0.75-1.48; P=0.75) post-dose 2. The relative incidence of intussusception within 7 days of vaccination was 6.49 post-dose 1 (95.5% CI: 4.17-10.09; P<0.001) and 1.29 post-dose 2 (95.5% CI: 0.80-2.11; P=0.29). Clustering of intussusception within 7 days of vaccination was observed post-dose 1. An attributable risk of 3 to 4 additional cases of intussusception per 100,000 vaccinated infants was estimated.

CONCLUSION

This is the largest surveillance study for intussusception after rotavirus vaccination to date. A temporal increase in the risk for intussusception was seen within 7 days of administration of the first vaccine dose. It is still uncertain whether rotavirus vaccination has any impact on the overall incidence of intussusception. This finding has to be put in perspective with the well-documented substantial benefits of rotavirus vaccination.

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

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.