Sociodemographic and dietary risk factors for natural infant intussusception in the United States

Profile and Epidemiology of Intussusception in Children Under-Two Years of Age: A Prospective Surveillance

OBJECTIVE

To report background intussusception epidemiology in children under-two years in Coimbatore district of Tamil Nadu state, India, prior to rotavirus vaccine (RVV) introduction.

METHODS

Prospective sentinel surveillance was done at four hospitals in Coimbatore during April 2016 to September 2017. The children aged >1 mo and < 24 mo with diagnosed intussusception were recruited and data on clinical, treatment, diet, immunization, and sociodemography were collected.

RESULTS

Sixty-eight children with intussusception were recruited. Among them 76.5% were infants with male predominance (57.4%) and 48.5% were 4-8 mo old. Vomiting (83.8%), pain in abdomen (including excessive crying) (72.1%), and bloody stools (45.6%) were the main symptoms. Reduction was tried in 92.6% cases with success in 83.8%. Surgery was needed by 16.2% children. No child died. Any RVV dose was received by 24.1% children and 2 children received RVV in 8-21 d and none within 1-7 d window. The incidence of intussusception requiring hospitalization was estimated to be 36.4 and 11.7 cases/100,000 children/y for the first and second years, respectively.

CONCLUSION

Intussusception occurred in infants even without RVV exposure. Continued surveillance is needed to document the changes in intussusception epidemiology after RVV introduction.

Incidence of intussusception before and after the introduction of rotavirus vaccine in Korea

Background

Recent studies have reported that after the introduction of rotavirus vaccine the incidence of intussusception did not change among infants, or slightly increased at the age immediately after the first dose. The rotavirus vaccines were introduced in Korea for private market use in 2007–2008. We investigated the incidence of intussusception before (2002–2006) and after (2009–2015) the vaccine introduction in Korea.

Methods

We conducted an interrupted time series study that used data from the Korean National Health Insurance database to identify infants (<12 months of age) who were diagnosed with intussusception and underwent non-invasive or invasive reduction from 2002 to 2015. According to the recommended ages for immunization, the annual intussusception incidence and the incidence rate ratios were calculated among three age groups, 6–14, 15–24, and 25–34 weeks.

Results

The annual incidences in infants have decreased over time from 241.7 per 100,000 infants (pre-vaccine period) to 160.1–205.2 per 100,000 infants (post-vaccine period). The incidence rate ratio during the post-vaccine period ranged from 0.66 to 0.85. The incidences of intussusception in all three infant age groups have decreased in post-vaccine period compared to pre-vaccine period (incidence rate ratio range: 0.31–0.65, 0.47–0.75, and 0.68–0.94 in 6–14, 15–24, and 25–34 weeks, respectively).

Conclusions

The incidence of intussusception in infants did not increase after the rotavirus vaccine introduction in Korea, but rather decreased over the past decades. Since the incidence of intussusception varies according to country or region, continuous monitoring the incidence of intussusception in infants is necessary in each county or region.

Overview of the Development, Impacts, and Challenges of Live-Attenuated Oral Rotavirus Vaccines

Safety, efficacy, and cost-effectiveness are paramount to vaccine development. Following the isolation of rotavirus particles in 1969 and its evidence as an aetiology of severe dehydrating diarrhoea in infants and young children worldwide, the quest to find not only an acceptable and reliable but cost-effective vaccine has continued until now. Four live-attenuated oral rotavirus vaccines (LAORoVs) (Rotarix^®, RotaTeq^®, Rotavac^®, and RotaSIIL^®) have been developed and licensed to be used against all forms of rotavirus-associated infection. The efficacy of these vaccines is more obvious in the high-income countries (HIC) compared with the low- to middle-income countries (LMICs); however, the impact is far exceeding in the low-income countries (LICs). Despite the rotavirus vaccine efficacy and effectiveness, more than 90 countries (mostly Asia, America, and Europe) are yet to implement any of these vaccines. Implementation of these vaccines has continued to suffer a setback in these countries due to the vaccine cost, policy, discharging of strategic preventive measures, and infrastructures. This review reappraises the impacts and effectiveness of the current live-attenuated oral rotavirus vaccines from many representative countries of the globe. It examines the problems associated with the low efficacy of these vaccines and the way forward. Lastly, forefront efforts put forward to develop initial procedures for oral rotavirus vaccines were examined and re-connected to today vaccines.

A case-control study of risk factors for intussusception among infants in eastern France after the introduction of the rotavirus vaccine

OBJECTIVE

The objective of the present study was to investigate the risk factors for intussusception (IS) among infants, including vaccination against rotavirus.

METHODS

Case-control study with systematic inclusion of all infants aged <1 year with suspected IS admitted to emergency departments in the eastern region of France between 1 April 2008 and 31 March 2012. All cases classed level 1 according to the Brighton classification were matched to 4 hospital controls. Two exposure windows were examined; exposure to the first dose of rotavirus vaccine in the 7 and in the 14 days prior to the occurrence of IS.

RESULTS

A total of 115 cases were matched with 457 controls. The average vaccination coverage rate over the 4 years of study was 8.6%. Rotavirus vaccine was not found to be significantly associated with the occurrence of IS in the 7 days (odds ratio (OR) not calculated; p = 0.99) and in the 14 days after administration of one dose vaccine (OR 1.33, 95% confidence interval (CI) 0.14-12.82). Infant formula alone or combined with breastfeeding was associated with an excess risk of IS (OR 2.74, 95% CI 1.10-6.79). A history of gastroenteritis within 2 weeks prior to hospitalisation was also associated with an increased risk (OR 2.24, 95% CI 1.07-4.67).

CONCLUSION

Our study indicates that infant formula alone or combined with breastfeeding is a risk factor for IS. A small, non-significant increase in the risk of IS was observed after rotavirus vaccination, although the low vaccine coverage rate likely precluded detection of a significant increase in risk.

Rotavirus vaccination and short-term risk of adverse events in US infants

BACKGROUND

The aim of this study was to evaluate the short-term risk of adverse events associated with rotavirus vaccine (RV) in infants, overall and by vaccine formulation (three-dose pentavalent, RV5; two-dose monovalent, RV1).

METHODS

We identified US newborns with commercial insurance during 2006-2014 receiving a diphtheria-tetanus-pertussis vaccine (DTaP) dose and assessed if RV was administered concurrently. We followed infants for 30 days after each dose for diagnoses of intussusception, other gastrointestinal events, seizures, Kawasaki disease, thrombocytopenia, otitis media, all-cause emergency department visits, and all-cause hospitalisations. We estimated adjusted hazard ratios (HR) and 95% confidence intervals (CI) with multivariable Cox proportional hazards models comparing: (a) those receiving DTaP+RV vs those receiving DTaP alone; and (b) RV5 vs RV1. Analyses were performed separately within DTaP doses and then meta-analysed across doses.

RESULTS

We identified 1 031 431 first DTaP doses, 821 833 second doses, and 615 293 third doses; 79.2% had a concurrent RV, 94.1% of which were RV5. Absolute risks of serious outcomes were very low. Compared to infants who received DTaP alone, infants who received RV+DTaP did not experience consistently increased risk of intussusception (hazard ratio [HR] 1.13, 95% confidence interval [CI] 0.68, 1.88) or any other outcome except for otitis media after dose 2: HR 1.11, 95% CI 1.08, 1.15. This increased otitis media risk was not as pronounced in RV5 when comparing RV5 to RV1; HR 0.92, 95% CI 0.89, 0.95.

CONCLUSIONS

These data were not consistent with an increased risk of intussusception or other adverse events following vaccination with RV, except potentially for a small increased risk of otitis media, particularly in RV1.

Universal rotavirus vaccination program in Sicily: Reduction in health burden and cost despite low vaccination coverage

Rotavirus is considered the main cause of severe gastroenteritis and nosocomial infections in Pediatric units, especially during late winter and early spring season in temperate region. In 2013 Sicilian Region, for the first time in Italy, introduced universal Rotavirus vaccination. This study aims to estimate health and economic impact on rotavirus Gastroenteritis (RVGE) among children aged 0–59 months in Sicily, after rotavirus vaccine introduction.

We analyzed hospital discharge records including a diagnosis of RVGE occurred from 1^st January 2009 to 31^st December 2016 among hospitalized children aged 0 to 59 months, residents in Sicily. RVGEs were defined as all hospitalizations with an ICD-9-CM diagnosis code of 008.61 on first or any diagnosis position. Also an economic impact analysis on Health Regional System was conducted.

We observed a consistent decline of hospitalization after rotavirus vaccination introduction from 394 per 100,000 in 2009–2012 to 220 per 100,000 in 2013–2016. We found a change in the peak of reported cases by at least one month from March-April in the pre-vaccination period to May-June in the post-vaccination period. Since 2013, we estimated that the annual average cost saved is 1,134,056 € when considering direct and indirect costs to health care as well as vaccination costs.

Our study is the first analysis conducted as far as we are aware in a high-income setting with poor coverage (lower than 50%), demonstrating a significant reduction of RVGE hospitalizations in Sicily after vaccine introduction. Moreover, was observed a consistent impact of vaccination on health care cost saving.

Incidence of acute intussusception among infants in eastern France: results of the EPIstudy trial

The incidence of intussusception in infants varies around the world. The epidemiology of intussusception in France has never been prospectively studied. We performed a prospective observational study with systematic inclusion of all infants aged <1 year with suspected intussusception admitted to the emergency departments of the hospitals in the eastern region of France (98,000 live births per year), from 4/1/2008 to 3/31/2012. Cases were classified using the Brighton Collaboration classification. In total, 185 infants with suspected intussusception were included of which 169 were idiopathic intussusception. Among these 169 cases, 115 (68%) were classed as Brighton level 1 (confirmed cases). Overall incidence of intussusception over the 4 years of the study was 29.8 (95% CI 24.6-35.7) cases per 100,000 live births for level 1 and 37.5 (95% CI 31.7-44.2) cases per 100,000 live births for all cases (levels 1-4). Annual incidence rates of level 1 intussusception were as follows: 44 (95% CI 31.9-59.3), 30.9 (20.9-44.2), 21.7 (13.4-33.2) and 22.1 (13.7-33.8) per 100,000 live births in the 1st, 2nd, 3rd and 4th study years, respectively.

CONCLUSION

The incidence rate of intussusception in the eastern part of France is comparable to that of other European countries. There was a significant trend towards a decrease in the incidence of intussusception. What is known • Intussusception is the most frequent causes of intestinal obstruction in infants and young children. Overall incidence of intussusception in infants aged <1 year varies widely around the world. No specific epidemiological studies have not been conducted in France on intussusception. What is new: • This prospective and multicenter study provides important information about the epidemiology of intussusception in infants in France over a period of 4 years.

Vaccine adverse events in a safety net healthcare system and a managed care organization

BACKGROUND

The Institute of Medicine, in a 2013 report, recommended that the Vaccine Safety Datalink (VSD) expand collaborations to include more diversity in the study population. Kaiser Permanente Colorado (KPCO), an established VSD site, partnered with Denver Health (DH), an integrated safety net healthcare system, to demonstrate the feasibility of integrating DH data within the VSD. Prior to incorporating the data, we examined the identification of specific vaccine associated adverse events (VAEs) in these two distinct healthcare systems.

METHODS

We conducted retrospective cohort analyses within KPCO and DH to compare select VAEs between the two populations. We examined the following associations between January 1, 2004 and December 31, 2013: Measles, Mumps, and Rubella (MMR) vaccine and febrile seizures in children 2years and younger, intussusception after rotavirus vaccine in infants 4-34weeks, syncope after adolescent vaccines (Tetanus, Diphtheria, acellular Pertussis; Meningococcal and Human Papillomavirus) in adolescents 13-17years and medically attended local reactions after pneumococcal polysaccharide (PPSV23) vaccine in adults 65years and older. Both sites used similar data procurement methods and chart review processes.

RESULTS

For seizures after MMR vaccine (KPCO - 3.15vs. DH - 2.97/10,000 doses) and syncope after all adolescent vaccines (KPCO - 3.0vs. DH - 2.37/10,000 doses), the chart confirmed rates were comparable at the two sites. However, for medically attended local reactions after PPSV23, there were differences in chart confirmed rates between the sites (KPCO - 31.65vs. DH - 14.90/10,000 doses). For intussusception after rotavirus vaccine, the number of cases was too low to make a valid comparison (KPCO - 0vs. DH - 0.13/10,000 doses).

CONCLUSION

We demonstrated that data on important targeted VAEs can be captured at DH and rates appear similar to those at KPCO. Work is ongoing on the optimal approach to assimilate DH data as a potential safety net healthcare system in the VSD.

Hospitalization rates for intussusception in children aged 0-59 months from 2009 to 2014 in Italy

The real cause of intussusception is not fully understood and a variety of conditions have been associated with it (Meckel diverticulum, polyps, duplication cysts, parasites, Henoch-Schönlein purpura, cystic fibrosis, hemolytic-uremic syndrome and infectious gastroenteritis). Furthermore few European countries, following WHO recommendation to monitor baseline incidence of intussusception before implementation of immunization program for rotavirus, used intussusception rate as a baseline value to compare the same figures in the period before and after introduction of vaccination. In this study, data of intussusception hospitalizations occurred among Italian children aged 0 through 59 months from 2009 to 2014 were analyzed. A total amount of 3,088 children were included, accounting for a hospitalization rate of 20.2 per 100,000. Overall, the hospitalization rate for intussusception had a slight increase in trend from 2009 to 2014 (18%). In particular children 0-11 months had a hospitalization rate higher than 12-59 months with an aggregate value of 36 Vs. 16 per 100,000 respectively. Among all children hospitalized for intussusception a total of 239 (7.7%) had also a previous or concomitant hospitalization for gastroenteritis. This study demonstrates that Italian hospitalizations for intussusception are increasing by time and the role played by different risk factors, including acute gastroenteritis, have to be investigated in the future. These data could be useful to monitor intussusception hospitalization in the perspective of anti-rotavirus vaccination introduction in Italy.

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.

Intussusception and Monovalent Rotavirus Vaccination in Singapore: Self-Controlled Case Series and Risk-Benefit Study

OBJECTIVE

To investigate the association between monovalent human rotavirus vaccine (RV1) and intussusception among Asian infants and the impact of older age of vaccination. To perform risk-benefit analysis of RV1 vaccination programs in Singapore.

STUDY DESIGN

We performed a self-controlled case series by extracting intussusception cases in infants aged <12 months from hospital databases (2005-2012) and with vaccination histories from a national immunization registry. Relative incidences were calculated by comparing incidence during defined risk periods after vaccination with times outside these periods. In the risk benefit analysis, we estimated excess intussusception hospitalization in relation to the number of infants vaccinated for hypothetical vaccination coverage scenarios.

RESULTS

There were 86 infants hospitalized with intussusception; 20 cases had received at least 1 dose of RV1. Nearly all (19) had received their first dose at age >12 weeks old. The age-adjusted relative incidence of intussusception in the 1- to 7-day period post dose one was 8.36 (95% CI 2.42-28.96). Of all childhood hospitalizations because of rotavirus, 71% (570 cases) could be prevented with 90% vaccination coverage. There would be approximately 1 excess intussusception case per 65,000 infants vaccinated.

CONCLUSIONS

Risk of intussusception increases about 8-fold during 1-7 days after receipt of first dose RV1 in infants of Chinese, Malay, and Indian ethnicity in Singapore, Asia. High vaccine coverage program in Singapore would be beneficial with only a low risk of excess intussusception. The relative risk of intussusception post-RV1 vaccination is not higher in Asia despite differences in background intussusception incidence compared with US and Australia, or older age of vaccination.

Incidence and risk factors for intussusception among children in northern Israel from 1992 to 2009: a retrospective study

Background

Determining the background incidence of intussusception is important in countries implementing rotavirus immunization. Rotavirus immunization was introduced into the routine infant immunization program in Israel during late 2010. Incidence and risk factors for intussusception were examined in children aged less than five years between 1992 and 2009.

Methods

Data were collected from medical records of children hospitalized due to intussusception (N = 190), and from control children (N = 295), at Carmel and Hillel Yaffe hospitals in northern Israel.

Results

The average annual incidence of intussusception in Jewish and Arab children aged less than five years was estimated at 36.1 (95% CI 17.0-76.5) vs. 23.2 per 100,000 (95% CI 9.3-57.9); for infants less than 12 months of age- 128.1 (95% CI 53.0-309.6) vs. 80.1 (95% CI 29.1-242.6) per 100,000. The risk of intussusception was higher in infants aged 3–5 months: OR 5.30 (95% CI 2.11-13.31) and 6–11 months: OR 2.53 (95% CI 1.13-5.62) when compared to infants aged less than 3 months; in those living in low vs high socioeconomic communities: OR 2.81 (95% CI 1.45-5.43), and in children with recent gastroenteritis: OR 19.90 (95% CI 2.35-168.32) vs children without recent gastroenteritis. Surgical reduction was required in 23.2%. The likelihood of surgery was significantly increased in patients presenting with bloody stool, in Arabs and those who were admitted to Hillel Yaffe Hospital.

Conclusions

The incidence of intussusception prior to universal rotavirus immunization was documented in northern Israel. Despite the lower incidence, Arab patients underwent surgery more often, suggesting delayed hospital admission of Arab as opposed to Jewish patients.

Intussusception secondary to anaphylactic reaction to salmon roe (ikura)

Anaphylactic food reaction often involves gastrointestinal symptoms, such as vomiting and abdominal pain, but to date, there have been no publications documenting the association between food hypersensitivity and intussusception. Herein is reported the case of a 2-year-old boy with intussusception accompanied by anaphylactic food reaction. The patient without known allergies complained of severe abdominal pain following ingestion of salmon roe for the first time. Dyspnea, wheezing and generalized urticaria also developed. Subsequently, he had stools containing jelly-like blood with mucus. At hospital arrival, physical examination identified an abdominal mass in the right lower quadrant; imaging confirmed the diagnosis of colo-colic intussusception. This patient was successfully treated with enema and no pathological findings were identified via radiology. Laboratory results supported the presence of IgE-mediated allergy to salmon roe in the present patient. To our knowledge, this is the first report to describe the possible association between intussusception and a hypersensitive food reaction.

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.

Intussusception incidence among infants in the UK and Republic of Ireland: a pre-rotavirus vaccine prospective surveillance study

•

The pre-rotavirus vaccine incidence of intussusception among UK and Irish infants was 24.8 and 24.2/100,000 live births.

•

The highest incidence (50.3/100,000 live births) occurred in the fifth month of life (for England).

•

A seasonal trend in intussusception was observed with the incidence significantly increased during winter and spring.

•

Baseline rates will inform rotavirus vaccine-safety policy by enabling comparison with post-introduction incidence.

Introduction

Intussusception, an abdominal emergency in young children, has been linked to a previous vaccine used to prevent rotavirus gastroenteritis. Although this vaccine was withdrawn, recent studies have suggested a potential, very small increased risk of intussusception following the administration of newly developed rotavirus vaccines. We aimed to determine the baseline incidence of intussusception among infants in the UK and Republic of Ireland – prior to the imminent introduction of the rotavirus vaccine into the UK schedule this year.

Methods

Prospective, active surveillance via the established British Paediatric Surveillance Unit (BPSU) was carried out from March 2008 to March 2009. Clinicians across 101 National Health Service (and equivalent) hospitals, including 27 paediatric surgical centres, reported cases admitted for intussusception in the UK and Republic of Ireland. The standard Brighton Collaboration case definition was used with only definite cases included for incidence estimation.

Results

The study response rate was 94.5% (379 questionnaires received out of 401 case notifications). A total of 250 definite cases of intussusception were identified. The annual incidence among infants in the UK and Republic of Ireland was 24.8 (95% CI: 21.7–28.2) and 24.2 (95% CI: 15.0–37.0) per 100,000 live births. In the UK, the highest incidence occurred in Northern Ireland (40.6, 95% CI: 21.0–70.8), followed by Scotland (28.7, 95% CI: 17.5–44.3), England (24.2, 95% CI: 20.9–27.9), then Wales (16.9, 95% CI: 6.8–34.8). In England, regional incidence was highest in London and lowest in the West Midlands. By age, the highest incidence (50.3/100,000 live births, 95% CI: 33.4–72.7) occurred in the fifth month of life (for England). A seasonal trend in the presentation of intussusception was observed with the incidence significantly (p = 0.001) increased during winter and spring.

Conclusion

The baseline rates obtained in this study will inform rotavirus vaccine-safety policy by enabling comparison with post-introduction incidence.

Trends in intussusception hospitalizations among US infants before and after implementation of the rotavirus vaccination program, 2000-2009

BACKGROUND

Although US data have not documented an intussusception risk with current rotavirus vaccines, international data indicate a possible low risk, primarily after the first dose.

METHODS

Among infants in 26 US states comprising 75% of the birth cohort, we examined age-specific trends in population-level intussusception hospitalization rates before (2000-2005) and after (2007-2009) rotavirus vaccine introduction.

RESULTS

Compared with 2000-2005 (35.3 per 100,000), the rate was greater in 2007 (39.0 per 100,000; rate ratio [RR], 1.10; 95% confidence interval [CI], 1.04-1.18), similar in 2008 (33.4 per 100,000; RR, 0.95; 95% CI, .89-1.01), and lower in 2009 (32.9 per 100,000; RR, 0.93; 95% CI, .87-.99). Among infants aged 8-11 weeks, compared with 2000-2005 (6.9 per 100,000), a small, significant increase was observed in each of 2007 (11.4 per 100,000; RR, 1.64; 95% CI, 1.08-2.50), 2008 (12.2 per 100,000; RR, 1.76; 95% CI, 1.17-2.65), and 2009 (11.0 per 100,000; RR, 1.59; 95% CI, 1.04-2.44).

CONCLUSIONS

Following rotavirus vaccine introduction, a small increase in intussusception rates was seen among US infants aged 8-11 weeks, to whom most first doses of vaccine are given; no sustained population-level change in overall rates was observed.