James P. Alexander

Active, Population-Based Surveillance for Severe Rotavirus Gastroenteritis in Children in the United States

OBJECTIVES. Routine vaccination of US infants against rotavirus was implemented in 2006, prompting the Centers for Disease Control and Prevention New Vaccine Surveillance Network to begin population-based acute gastroenteritis surveillance among US children <3 years of age. This surveillance system establishes baseline estimates of rotavirus disease burden and allows for the prospective monitoring of rotavirus vaccination impact. METHODS. Eligible children with acute gastroenteritis (≥3 episodes of diarrhea and/or any vomiting in a 24-hour period) who were hospitalized, were seen in emergency departments, or visited selected outpatient clinics in 3 US counties during the period of January through June 2006 were enrolled. Epidemiological and clinical information was obtained through parental interview and medical chart review, and stool specimens were tested for rotavirus with enzyme immunoassays. Rotavirus-positive specimens were genotyped by using reverse transcription-polymerase chain reaction assays. RESULTS. Stool specimens were collected from 516 of the 739 enrolled children with acute gastroenteritis (181 inpatient, 201 emergency department, and 134 outpatient) and 44% tested positive for rotavirus (227 of 516 specimens). The most common strain was P[8]G1 (84%), followed by P[4]G2 (5%) and P[6]G12 (4%). None of the 516 children had received rotavirus vaccine. The rotavirus detection rate was 50% for hospitalized acute gastroenteritis cases, 50% for emergency department visits, and 27% for outpatient visits. Rotavirus-related acute gastroenteritis cases were more likely than non–rotavirus-related acute gastroenteritis cases to present with vomiting, diarrhea, fever, and lethargy. Directly calculated, population-based rates for rotavirus hospitalizations and emergency department visits were 22.5 hospitalizations and 301.0 emergency department visits per 10 000 children <3 years of age, respectively. A sentinel outpatient clinic visit rate of 311.9 outpatient visits per 10 000 children <3 years of age was observed. CONCLUSIONS. Population-based, laboratory-confirmed rotavirus surveillance in the final rotavirus season before implementation of the US rotavirus vaccine program indicated a considerable burden of disease on the US health care system.

Transmission of Imported Vaccine-Derived Poliovirus in an Undervaccinated Community in Minnesota

BACKGROUND Oral poliovirus vaccine (OPV) has not been used in the United States since 2000. Type 1 vaccine-derived poliovirus (VDPV) was identified in September 2005, from an unvaccinated Amish infant hospitalized in Minnesota with severe combined immunodeficiency. An investigation was conducted to determine the source of the virus and its means of transmission. METHODS The infant was tested serially for poliovirus excretion. Investigations were conducted to detect poliovirus infections or paralytic poliomyelitis in Amish communities in Minnesota, neighboring states, and Ontario, Canada. Genomic sequences of poliovirus isolates were determined for phylogenetic analysis. RESULTS No source for the VDPV could be identified. In the index community, 8 (35%) of 23 children tested, including the infant, had evidence of type 1 poliovirus or VDPV infection. Phylogenetic analysis suggested that the VDPV circulated in the community for approximately 2 months before the infants infection was detected and that the initiating OPV dose had been given before her birth. No paralytic disease was found in the community, and no poliovirus infections were found in other Amish communities investigated. CONCLUSIONS This is the first demonstrated transmission of VDPV in an undervaccinated community in a developed country. Continued vigilance is needed in all countries to identify poliovirus infections in communities at high risk of poliovirus transmission.

Will Pediatricians Adopt the New Rotavirus Vaccine

OBJECTIVES. Our objective was to determine the following among US pediatricians: (1) perceptions regarding burden of rotavirus disease and need for a vaccine; (2) intentions for recommending a newly licensed rotavirus vaccine; (3) perceived barriers to implementation; and (4) factors associated with plans for vaccine adoption. PATIENTS AND METHODS. A network of 431 pediatricians was recruited from a random sample of American Academy of Pediatrics’ members. The network was designed to be representative of the American Academy of Pediatrics with respect to region of the country, practice type, and practice setting. During January and February 2006, physicians were surveyed by Internet or mail. The survey contained a paragraph summarizing results of the new rotavirus vaccine trial. Respondents were asked about intentions to use the vaccine and anticipated barriers. RESULTS. The survey response rate was 71%. Of the respondents, 52% strongly agreed and 37% somewhat agreed with the need for a rotavirus vaccine. If recommended for routine use, 50% would strongly recommend and 34% would recommend but not strongly; 52% would begin to use within 6 months and 27% from 6 months to 1 year. The top 3 “definite” barriers to implementation included concerns about uniform coverage of vaccine by insurers, lack of adequate reimbursement, and parental reluctance because of withdrawal of previous rotavirus vaccine. In multivariate analysis, factors associated with very likely adoption of the vaccine included perception of a high burden of rotavirus disease and a high level of confidence in prelicensure studies of vaccine safety. The presence of physician concerns about safety of the new vaccine and the perception of parental concerns about vaccine safety in general were negatively associated with adoption. CONCLUSIONS. The majority of pediatricians reported willingness to implement the new rotavirus vaccine, most within 6 months. Major barriers to optimal implementation included provider concerns about reimbursement issues and parental acceptance of the vaccine.

Seroprevalence of Antibody to Mumps Virus in the US Population, 1999–2004

BACKGROUND In 2006, the largest mumps outbreak in the United States in 20 years occurred. To understand prior mumps seroprevalence and factors associated with the presence of antibody to mumps virus, data from the 1999-2004 National Health and Nutrition Examination Survey (NHANES) were analyzed. METHODS A mumps virus-specific enzyme immunoassay was used to measure the seroprevalence of serum immunoglobulin G (IgG) antibody among NHANES participants aged 6-49 years. Participants were grouped on the basis of 10-year birth cohorts, 95% confidence intervals (CIs) were calculated using SUDAAN software, and logistic regression was used to identify independent predictors. RESULTS The overall age-adjusted seroprevalence of IgG antibody to mumps virus during 1999-2004 was 90.0% (95% CI, 88.8%-91.1%). Seroprevalence was higher among US-born non-Hispanic blacks (96.4% [95% CI, 95.5%-97.2%]) and non-US-born Mexican Americans (93.7% [95% CI, 92.0%-95.2%]). Seroprevalence was significantly lower in the 1967-1976 birth cohort (85.7% [95% CI, 83.5%-87.8%]). The variables sex, education, and race/ethnicity/birthplace were independent predictors in at least 1 of the birth cohorts. CONCLUSIONS The overall estimate of 90.0% is at the lower end of the estimated population immunity (90%-92%) needed to achieve herd immunity. Lower seroprevalence among groups suggest that they represent populations at an increased risk. For mumps control, high vaccine coverage and high population immunity must be achieved and maintained.

Trends in the risk of U.S. polio outbreaks and poliovirus vaccine availability for response.

Objectives. The United States eliminated indigenous wild polioviruses (WPVs) in 1979 and switched to inactivated poliovirus vaccine in 2000, which quickly ended all indigenous live poliovirus transmission. Continued WPV circulation and use of oral poliovirus vaccine globally allow for the possibility of reintroduction of these viruses. We evaluated the risk of a U.S. polio outbreak and explored potential vaccine needs for outbreak response. Methods. We synthesized information available on vaccine coverage, exemptor populations, and population immunity. We used an infection transmission model to explore the potential dynamics of a U.S. polio outbreak and potential vaccine needs for outbreak response, and assessed the impacts of heterogeneity in population immunity for two different subpopulations with potentially low coverage. Results. Although the risk of poliovirus introduction remains real, widespread transmission of polioviruses appears unlikely in the U.S., given high routine coverage. However, clusters of un- or underimmunized children might create pockets of susceptibility that could potentially lead to one or more paralytic polio cases. We found that the shift toward combination vaccine utilization, with limited age indications for use, and other current trends (e.g., decreasing proportion of the population with immunity induced by live polioviruses and aging of vaccine exemptor populations) might increase the vulnerability to poliovirus reintroduction at the same time that the ability to respond may decrease. Conclusions. The U.S. poliovirus vaccine stockpile remains an important resource that may potentially be needed in the future to respond to an outbreak if a live poliovirus gets imported into a subpopulation with low vaccination coverage.

Progress and Peril: Poliomyelitis Eradication Efforts in Pakistan, 1994–2013

Pakistan is one of 3 countries where transmission of indigenous wild poliovirus (WPV) has never been interrupted. Numbers of confirmed polio cases have declined by >90% from preeradication levels, although outbreaks occurred during 2008-2013. During 2012 and 2013, 58 and 93 WPV cases, respectively, were reported, almost all of which were due to WPV type 1. Of the 151 WPV cases reported during 2012-2013, 123 (81%) occurred in the conflict-affected Federally Administered Tribal Areas (FATA) and in security-compromised Khyber Pakhtunkhwa province. WPV type 3 was isolated from only 3 persons with polio in a single district in 2012. During August 2012-December 2013, 62 circulating vaccine-derived poliovirus type 2 cases were detected, including 40 cases (65%) identified in the FATA during 2013. Approximately 350 000 children in certain districts of the FATA have not received polio vaccine during supplementary immunization activities (SIAs) conducted since mid-2012, because local authorities have banned polio vaccination. In other areas of Pakistan, SIAs have been compromised by attacks targeting polio workers, which started in mid-2012. Further efforts to reach children in conflict-affected and security-compromised areas will be necessary to prevent reintroduction of WPV into other areas of Pakistan and other parts of the world.

Hepatitis B control among children in the Eastern Mediterranean Region of the World Health Organization

In the pre-vaccination era, the prevalence of chronic hepatitis B virus (HBV) infection in the World Health Organization (WHO) Eastern Mediterranean Region (EMR) ranged from two to seven percent in a total population of over 580 million people. Mortality estimates place cirrhosis among the top ten causes of years of life lost in the EMR. The region has made notable achievements, improving coverage from only 6% in 1992, when WHO recommended hepatitis B vaccination of all infants, to 83% in 2014. Member states adopted a hepatitis B control target in 2009 to reduce chronic hepatitis B virus infection prevalence to less than one percent among children aged <5 years by 2015. This report reviews progress toward achievement, challenges faced, and the next steps forward of hepatitis B control among children in the EMR.

Progress toward Elimination of Hepatitis B Virus Transmission in Oman: Impact of Hepatitis B Vaccination

Approximately 2-7% of the Omani population has chronic hepatitis B virus (HBV) infection. To decrease this burden, universal childhood hepatitis B vaccination was introduced in Oman in 1990. The hepatitis B vaccination strategy and reported coverage were reviewed. To assess the impact of the program on chronic HBV seroprevalence, a nationally representative seroprevalence study was conducted in Oman in 2005. Since 1991, hepatitis B vaccination in Oman has reached almost every eligible child, with reported coverage of ≥ 97% for the birth dose and ≥ 94% for three doses. Of 175 children born pre-vaccine introduction, 16 (9.1%) had evidence of HBV exposure, and 4 (2.3%) had evidence of chronic infection. Of 1,890 children born after vaccine introduction, 43 (2.3%) had evidence of HBV exposure, and 10 (0.5%) had evidence of chronic infection. Oman has a strong infant hepatitis B vaccination program, resulting in a dramatic decrease in chronic HBV seroprevalence.

Progress Toward Measles Elimination — Nepal, 2007–2014

In 2013, the 66th session of the Regional Committee of the World Health Organization (WHO) South-East Asia Region (SEAR) established a goal to eliminate measles and to control rubella and congenital rubella syndrome (CRS) in SEAR by 2020. Current recommended measles elimination strategies in the region include 1) achieving and maintaining ≥95% coverage with 2 doses of measles-containing vaccine (MCV) in every district, delivered through the routine immunization program or through supplementary immunization activities (SIAs); 2) developing and sustaining a sensitive and timely measles case-based surveillance system that meets minimum recommended performance indicators; 3) developing and maintaining an accredited measles laboratory network; and 4) achieving timely identification, investigation, and response to measles outbreaks. In 2013, Nepal, one of the 11 SEAR member states, adopted a goal for national measles elimination by 2019. This report updates a previous report and summarizes progress toward measles elimination in Nepal during 2007-2014. During 2007-2014, estimated coverage with the first MCV dose (MCV1) increased from 81% to 88%. Approximately 3.9 and 9.7 million children were vaccinated in SIAs conducted in 2008 and 2014, respectively. Reported suspected measles incidence declined by 13% during 2007-2014, from 54 to 47 cases per 1 million population. However, in 2014, 81% of districts did not meet the measles case-based surveillance performance indicator target of ≥2 discarded non-measles cases per 100,000 population per year. To achieve and maintain measles elimination, additional measures are needed to strengthen routine immunization services to increase coverage with MCV1 and a recently introduced second dose of MCV (MCV2) to ≥95% in all districts, and to enhance sensitivity of measles case-based surveillance by adopting a more sensitive case definition, expanding case-based surveillance sites nationwide, and ensuring timely transport of specimens to the accredited national laboratory.

Measles and rubella elimination: learning from polio eradication and moving forward with a diagonal approach

ABSTRACT Introduction: In 1988, an estimated 350,000 children were paralyzed by polio and 125 countries reported polio cases, the World Health Assembly passed a resolution to achieve polio eradication by 2000, and the Global Polio Eradication Initiative (GPEI) was established as a partnership focused on eradication. Today, following eradication efforts, polio cases have decreased >99% and eradication of all three types of wild polioviruses is approaching. However, since polio resources substantially support disease surveillance and other health programs, losing polio assets could reverse progress toward achieving Global Vaccine Action Plan goals. Areas covered: As the end of polio approaches and GPEI funds and capacity decrease, we document knowledge, experience, and lessons learned from 30 years of polio eradication. Expert commentary: Transitioning polio assets to measles and rubella (MR) elimination efforts would accelerate progress toward global vaccination coverage and equity. MR elimination feasibility and benefits have long been established. Focusing efforts on MR elimination after achieving polio eradication would make a permanent impact on reducing child mortality but should be done through a ‘diagonal approach’ of using measles disease transmission to identify areas possibly susceptible to other vaccine-preventable diseases and to strengthen the overall immunization and health systems to achieve disease-specific goals.