Secular variation in United States rotavirus disease rates and serotypes: implications for assessing the rotavirus vaccination program

Effectiveness of pentavalent rotavirus vaccine against severe disease

OBJECTIVE

To determine the vaccine effectiveness (VE) of complete and partial vaccination with the pentavalent rotavirus vaccine (RV5) in the prevention of rotavirus acute gastroenteritis (AGE) hospitalizations and emergency department visits during the first 3 rotavirus seasons after vaccine introduction.

METHODS

Active, prospective population-based surveillance for AGE and acute respiratory infection (ARIs) in inpatient and emergency department settings provided subjects for a case-control evaluation of VE in 3 US counties from January 2006 through June 2009. Children with laboratory-confirmed rotavirus AGE (cases) were matched according to date of birth and onset of illness to 2 sets of controls: children with rotavirus-negative AGE and children with ARI. The main outcome measure was VE with complete (3 doses) or partial (1 or 2 doses) RV5 vaccination.

RESULTS

Of age-eligible children enrolled, 18% of cases, 54% of AGE controls, and 54% of ARI controls received ≥1 dose of RV5. The VE of RV5 for 1, 2, and 3 doses against all rotavirus genotypes with the use of rotavirus-negative AGE controls was 74% (95% confidence interval [CI]: 37%-90%), 88% (95% CI: 66%-96%), and 87% (95% CI: 71%-94%), respectively, and with the use of ARI controls was 73% (95% CI: 43%-88%), 88% (95% CI: 68%-95%), and 85% (95% CI: 72%-91%), respectively. The overall VE estimates were comparable during the first and second years of life and against AGE caused by different rotavirus strains.

CONCLUSION

RV5 was highly effective in preventing severe rotavirus disease, even after a partial series, with protection persisting throughout the second year of life.

Molecular and infectivity studies of porcine circovirus in vaccines

This report describes FDA's laboratory response to the 2010 reports that porcine circovirus type 1 (PCV-1) DNA was present in U.S.-licensed rotavirus vaccines and in cells used to produce inactivated poliovirus vaccines. In the present study, Rotarix® (GlaxoSmithKline, Rixenxart, Belgium) was found to contain full-length PCV-1 genomes that are particle-associated, and cell culture assays in swine testis (ST) and PCV-free porcine kidney (PK-15) cells confirmed that PCV-1 sequences in this vaccine represent infectious virus. RotaTeq® (Merck and Co., West Point, PA, USA) contained small PCV-1 and PCV-2 genome fragments, but did not contain detectable larger portions of (or full-length) PCV genomes, and cell culture assays did not amplify PCV from this vaccine. Inactivated poliovirus vaccine bulks (GlaxoSmithKline) were also negative for the presence of PCV by cell culture infectivity assay. In these vaccines, molecular characterization of PCV nucleic acids was useful for predicting the results of cell culture assays.

Decline in rotavirus hospitalisations following introduction of Australia's national rotavirus immunisation programme

AIM

To determine the impact of rotavirus immunisation on rotavirus hospitalisations in young children. methods: Annual hospitalisations for rotavirus gastroenteritis to The Children's Hospital at Westmead, a tertiary care paediatric hospital in Sydney, were recorded from 2001 for 6 years prior to and 2.5 years following the introduction of rotavirus vaccines to the National Immunisation Program. Data on hospital-acquired rotavirus gastroenteritis were collected prospectively.

RESULTS

Hospitalisations for rotavirus gastroenteritis declined in the two full rotavirus seasons (2008 and 2009) after vaccine introduction by 75% compared with mean annual hospitalisations from 2001 to 2006. The greatest decline was seen in those <12 months of age (93%), but the reduction occurred consistently across all age groups, even in children not eligible for immunisation, suggesting an effect on herd immunity. A substantial decline in nosocomial rotavirus gastroenteritis was seen from 2007 to 2009, suggesting a reduction in virus transmission in the hospital setting.

CONCLUSION

This study demonstrates a substantial reduction in hospitalisations in children of all ages to a large paediatric hospital and reduced nosocomial infections since the introduction of a nationally funded rotavirus immunisation programme in Australia.

Impact of rotavirus vaccination on diarrhea-related hospitalizations among children < 5 years of age in Mexico

BACKGROUND

Single-strain rotavirus vaccine was added to the national immunization program in Mexico in May 2007. We assessed the impact of vaccination on the number of diarrhea-related hospitalizations in Mexican children in 2008 and 2009.

METHODS

We obtained data on all-cause diarrhea-related hospitalizations from January 2003 to June 2009 in Mexican children <5 years of age. We compared diarrhea-related hospitalizations during the 2008 and 2009 rotavirus seasons with the median number of diarrhea-related hospitalizations at baseline (2003-2006), before rotavirus vaccine introduction, at 306 Ministry of Health hospitals. We estimated vaccine coverage using administrative data.

RESULTS

A median number of 10,993 diarrhea-related hospitalizations (range: 9877-11958) occurred each prevaccine rotavirus season from 2003 to 2006 among children < 5 years of age. Diarrhea-related hospitalizations decreased by 11% (N = 9836) in 2008 and by 40% (N = 6597) in 2009. The greatest declines occurred in infants < 12 months of age during 2008 (25%) and 2009 (52%), with 1-dose rotavirus vaccination coverage of 74% and 89% during these years, respectively. A 43% decline was also noted among children 12 to 23 months of age during the 2009 season. No declines were noted during either 2008 or 2009 among unvaccinated children >24 months of age during the study period.

CONCLUSIONS

Marked declines in diarrhea-related hospitalizations among vaccine-eligible Mexican children < 24 months of age have occurred during the first 2 complete rotavirus seasons following rotavirus vaccination. Rotavirus-specific surveillance and epidemiologic studies are necessary for a better understanding of the changes in disease epidemiology and public health impact from rotavirus vaccination.

Distribution of rotavirus genotypes after introduction of rotavirus vaccines, Rotarix® and RotaTeq®, into the National Immunization Program of Australia

BACKGROUND

Rotavirus vaccines, RotaTeq and Rotarix, were introduced into the Australian National Immunization Program on July 1, 2007. The simultaneous introduction in different Australian states and territories provides a unique opportunity to compare the affect of each vaccine on the types of circulating rotavirus strains. This report describes the rotavirus genotypes responsible for the hospitalization of children during the first 2-year period after vaccine introduction.

METHODS

A total of 764 rotavirus-associated diarrheal cases were collected from children presenting to hospital in 10 Australian centers. Rotavirus genotype was determined using reverse transcription polymerase chain reaction assays.

RESULTS

G1P[8] was the dominant genotype nationally (52%), followed by G2P[4] (19.8%), G9P[8] (12.2%), and G3P[8] (11%). Differences in the prevalence rates of G2P[4] and G3P[8] were seen in the various states. G2P[4] strains were more prevalent in states using Rotarix, whereas G3P[8] strains were more prevalent in states using RotaTeq.

CONCLUSIONS

Differences in rotavirus genotypes were observed across Australia, which suggest that different immune pressures are exerted by the different vaccines, but do not necessarily imply lack of protection by either vaccine. These differences may simply be related to the variation that can occur because of natural annual fluctuation in rotavirus strain prevalence.

Decline in rotavirus hospitalizations and health care visits for childhood diarrhea following rotavirus vaccination in El Salvador

BACKGROUND

A recent postlicensure study from El Salvador showed that the monovalent rotavirus vaccine conferred 76% protection against rotavirus hospitalizations. We further examined the impact of rotavirus vaccination on the national burden of childhood diarrhea to help assess the total public health benefits of vaccination.

METHODS

We compared all-cause diarrhea and rotavirus-specific hospitalization rates during prevaccine year 2006, with postvaccine years 2008 and 2009 in children < 5 years of age from 7 sentinel surveillance hospitals. We also compared annual rates of diarrhea-related healthcare events during prevaccine years 2005 and 2006 with postvaccine years 2008 and 2009 to examine the national burden of healthcare utilization for all-cause diarrhea.

RESULTS

Among sentinel surveillance hospitals, rotavirus hospitalization rates among children < 5 years of age declined by 81% (95% confidence interval [CI]: 78%-84%) in 2008 when 2-dose rotavirus vaccine coverage was 50% among infants < 1 year; the decline was 69% (95% CI: 65%-73%) in 2009 when 2-dose vaccine coverage was 61% among infants < 1 year, compared with 2006. The greatest declines were observed in children ≤ 1 year of age, although sizeable reductions were also observed among children ≥ 2 years in 2008. National diarrhea-related healthcare visits during rotavirus season decreased by 48% (95% CI: 47%-48%) in 2008 and by 35% (95% CI: 34%-35%) in 2009 compared with the mean rate from the 2005 and 2006 rotavirus seasons.

CONCLUSIONS

Rotavirus vaccination had a substantial public health impact on rotavirus disease and overall diarrhea events in El Salvador. Important age-related changes in diarrheal incidence emphasize the need for ongoing rotavirus surveillance after vaccine introduction.

Diarrhea-associated hospitalizations among US children over 2 rotavirus seasons after vaccine introduction

OBJECTIVE

After implementation of rotavirus vaccination in 2006, large decreases in rates of severe diarrhea among US children occurred in 2007-2008. We ascertained whether these decreases were sustained in 2008-2009.

METHODS

We examined hospital discharge data from a national network of pediatric hospitals and compared all-cause diarrhea-related and rotavirus-specific hospitalizations in 3 prevaccine rotavirus seasons (2003-2006) with those in 2 postvaccine seasons (2007-2008 and 2008-2009) among children <5 years of age. We defined rotavirus seasons using data from a national laboratory surveillance network.

RESULTS

At 62 consistently reporting hospitals, a median of 15 645 diarrhea-related hospitalizations (range: 14 881-16 884 hospitalizations) occurred each rotavirus season among children <5 years of age in 2003-2006. Compared with this median, all-cause diarrhea-related hospitalizations decreased by 50% (n = 7760) in 2007-2008 and by 29% (n = 11 039) in 2008-2009. In 2007-2008, reductions of 47% to 55% were seen for all age groups, including vaccine-ineligible children ≥2 years of age (48%). In 2008-2009, these reductions decreased in magnitude, especially among children ≥2 years of age (17%). Decreases in 2007-2008 and 2008-2009 were similar in the Northeast and West, but decreases were smaller in 2008-2009, compared with 2007-2008, in the Midwest and South.

CONCLUSIONS

Compared with prevaccine seasons, decreases in diarrhea- and rotavirus-associated hospitalizations seen in 2007-2008 were sustained in 2008-2009 but were somewhat smaller. Given the variability in diarrhea-related hospitalization trends over the 2 postvaccine seasons according to age group and region, continued surveillance is required for full assessment of the impact of rotavirus vaccination.

The structure, role, and procedures of the U.S. Advisory Committee on Immunization Practices (ACIP)

The National Immunization Technical Advisory Group (NITAG) in the United States is the Advisory Committee on Immunization Practices (ACIP). The ACIP was established in 1964 by the US Surgeon General to assist in the prevention and control of communicable diseases, and includes a chair, an executive secretary, 15 voting members, 8 ex officio members and liaison representatives from 26 health-related professional organizations. Meetings are regularly convened at the Centers for Disease Control and Prevention (CDC) and are open to the public. Stringent measures and rigorous screening are used to avoid both real and apparent conflicts of interest, and no special interest or lobbying groups provide any material support to ACIP or its members. The committee recommends licensed new vaccines to be incorporated into the routine immunization schedule, recommends vaccine formulations, and reviews older vaccines to consider revising its recommendations.

Estimating the rotavirus hospitalization disease burden and trends, using capture-recapture methods

BACKGROUND

Rotavirus surveillance is needed to provide estimates of disease burden and to evaluate the effect of vaccination programs. Our objective was to use capture-recapture methods to estimate rotavirus hospitalization rates and to examine trends over time.

METHODS

Children <3 years of age residing in Hamilton County, Ohio hospitalized with acute gastroenteritis, and laboratory-confirmed rotavirus between 1997 and 2008 were identified through 2 independent surveillance systems: an active system with prospective enrollment of children admitted with acute gastroenteritis and a passive system of children identified by rotavirus testing as part of their usual medical care. Capture-recapture methods compared cases from both systems to estimate the number of missed cases from either system. Using census data for Hamilton County, rates per 10,000 with 95% confidence intervals (CI) for rotavirus hospitalizations were estimated.

RESULTS

Overall, 486 cases were identified using active surveillance and 244 using passive surveillance, with 127 cases captured by both. Using capture-recapture methods, the overall rate in children <3 years old was 26.9/10,000; CI: 24.1, 30.6. Rates varied by year: highest in 1998 (48.1/10,000; CI: 32.4, 92.2) and lowest in 2008 (3.2/10,000; CI: 2.1, 6.1) after rotavirus vaccine introduction. Among children <5 years old, rates were highest in <3-month-old children (51.8/10,000; CI: 39.4, 75.1) and lowest in older age groups: 24 to 35 months (20.5/10,000; CI: 14.7, 30.3) and 36 to 59 months (4.1/10,000; CI: 2.9, 7.2). Rates from capture-recapture methods and adjusted active system were comparable.

CONCLUSIONS

Capture-recapture methods were a useful tool to estimate rotavirus disease burden and to monitor trends, especially in the era of rotavirus immunization.

A hospital based study on inter- and intragenotypic diversity of human rotavirus A VP4 and VP7 gene segments, Germany

BACKGROUND

Efforts to reduce the impact of group A rotaviruses on human morbidity and mortality rely on oral immunisation with live attenuated or recombinant vaccines. A major challenge in immunisation is the vast inter- and intragenotypic diversity accomplished by circulating rotaviruses.

OBJECTIVES

To monitor rotavirus inter- and intragenotypic diversity in hospitalised children.

STUDY DESIGN

From January 2008 to December 2009 stool samples from 1994 paediatric in-patients suffering from diarrhoea were screened for rotavirus. Rotavirus G- and P-genotypes were determined by nucleotide sequencing and phylogenetic analysis was performed.

RESULTS

Rotavirus A was detected in stool samples of 341 children, comprising G1P[8], G2P[4], G3P[8], G4P[8], G9P[8], as well as uncommon G12P[6] genotypes and mixed infections. Predominant strains shifted from G1P[8] and G9P[8] genotypes in the first season to G3P[8] and G4P[8] genotypes in the second season. The highest intragenotypic diversity was detected in G1 strains and consisted of co-circulating G1-Ic, G1-Id, G1-Ie and G1-II rotaviruses. The G2 analysis revealed different intragenotypic lineages: G2-IIa, G2-IIb and G2-IIc. Interestingly, the circulating G4-Ib rotaviruses were characterised by insertions of 3 or 6 additional coding nucleotides within variable region 4 of VP7. Whereas different G9-III VP7 gene segments were detected G3-Ia sequences were highly homologous. In the VP4 analysis P[8]-III gene segment predominated over P[4]-Vb, P[8]-I, P[8]-IV and P[6]-I.

CONCLUSIONS

A remarkable rotavirus heterogeneity was detected in the limited local setting and time span. Continued monitoring and nucleotide sequencing is necessary to document possible effects of rising immunisation levels on intragenotypic rotavirus diversity.

Global impact of rotavirus vaccines

The WHO has recently recommended the inclusion of rotavirus vaccine in the national immunization programs of all countries. In countries in the Americas, Europe and Australia that have adopted routine childhood immunization against rotavirus, significant reductions in the burden of severe childhood diarrhea have been observed. Besides protecting vaccinated children, disease rates also appear to be reduced in unvaccinated children, suggesting indirect benefits from vaccination (i.e., herd protection). Early clinical trial data from Africa and Asia are promising, and further efforts are needed to optimize the benefits of vaccination in developing countries where vaccines are likely to have their greatest impact.

Prevention of rotavirus gastroenteritis in infants and children: rotavirus vaccine safety, efficacy, and potential impact of vaccines

Rotavirus infection is the most common cause of severe gastroenteritis globally, with greater than 86% of deaths occurring in low-income and middle-income countries. There are two rotavirus vaccines currently licensed in the United States and prequalified by the World Health Organization. RV1 is a monovalent attenuated human rotavirus strain, given orally in two doses. RV5 is a pentavalent human-bovine reassortant rotavirus vaccine, given orally in three doses. A third rotavirus vaccine, LLV, is a lamb rotavirus strain given orally as a single dose, which is currently available only in China. RV1 and RV5 have been shown to be highly efficacious in developed countries, and initial results from trials in Africa and Asia are promising as well. At least three other vaccines are in development, which are being developed by manufacturers of developing countries. Further studies are needed to clarify issues including administration of oral rotavirus vaccines with breastfeeding and other oral vaccines, and alterations in dosing schedule. Using new data on global diarrheal burden, rotavirus is estimated to cause 390,000 deaths in children younger than 5 years. Should rotavirus vaccines be introduced in the routine immunization programs of all countries, a potential of 170,000 deaths could be prevented annually. The largest impact on mortality would be seen in low-income and middle-income countries, despite poor immunization coverage and lower efficacy. Therefore, international efforts are needed to ensure that rotavirus vaccines reach the populations with highest burden of rotavirus disease.

Change in rotavirus epidemiology in northeast Florida after the introduction of rotavirus vaccine

Retrospective analysis done at a children's hospital showed significant decrease in infections and hospitalizations caused by rotavirus in northeast Florida after the introduction of rotavirus vaccines in 2006. The rotavirus season was delayed in onset by 8 months and duration prolonged by 2-3 months in 2008, and no definite season occurred in 2009.

Rotavirus infections and vaccines: burden of illness and potential impact of vaccination

Rotaviruses are the most common cause of severe gastroenteritis in children. By 5 years of age virtually every child worldwide will have experienced at least one rotavirus infection. This leads to an enormous disease burden, where every minute a child dies because of rotavirus infection and another four are hospitalized, at an annual societal cost in 2007 of $US2 billion. Most of the annual 527 000 deaths are in malnourished infants living in rural regions of low and middle income countries. In contrast, most measurable costs arise from medical expenses and lost parental wages in high income countries. Vaccines are the only public health prevention strategy likely to control rotavirus disease. They were developed to mimic the immunity following natural rotavirus infection that confers protection against severe gastroenteritis and consequently reduces the risk of primary healthcare utilization, hospitalization and death. The two currently licensed vaccines--one a single human strain rotavirus vaccine, the other a multiple strain human-bovine pentavalent reassortant rotavirus vaccine--are administered to infants in a two- or three-dose course, respectively, with the first dose given at 6-14 weeks of age. In various settings they are safe, immunogenic and efficacious against many different rotavirus genotypes. In high and middle income countries, rotavirus vaccines confer 85-100% protection against severe disease, while in low income regions of Africa and Asia, protection is less, at 46-77%. Despite this reduced efficacy in low income countries, the high burden of diarrheal disease in these regions means that proportionately more severe cases are prevented by vaccination than elsewhere. Post-licensure effectiveness studies show that rotavirus vaccines not only reduce rotavirus activity in infancy but they also decrease rates of rotavirus diarrhea in older and unimmunized children. A successful rotavirus vaccination program will rely upon sustained vaccine efficacy against diverse and evolving rotavirus strains and efficient vaccine delivery systems. The potential introduction of rotavirus vaccines into the world's poorest countries with the greatest rates of rotavirus-related mortality is expected to be very cost effective, while rotavirus vaccines should also be cost effective by international standards when incorporated into developed countries immunization schedules. Nonetheless, cost effectiveness in each country still depends largely on the local rotavirus mortality rate and the price of the vaccine in relation to the per capita gross domestic product.