Effectiveness of a Third Dose of MMR Vaccine for Mumps Outbreak Control.

BACKGROUND: The effect of a third dose of the measles-mumps-rubella (MMR) vaccine in stemming a mumps outbreak is unknown. During an outbreak among vaccinated students at the University of Iowa, health officials implemented a widespread MMR vaccine campaign. We evaluated the effectiveness of a third dose for outbreak control and assessed for waning immunity. METHODS: Of 20,496 university students who were enrolled during the 2015-2016 academic year, mumps was diagnosed in 259 students. We used Fisher's exact test to compare unadjusted attack rates according to dose status and years since receipt of the second MMR vaccine dose. We used multivariable time-dependent Cox regression models to evaluate vaccine effectiveness, according to dose status (three vs. two doses and two vs. no doses) after adjustment for the number of years since the second dose. RESULTS: Before the outbreak, 98.1% of the students had received at least two doses of MMR vaccine. During the outbreak, 4783 received a third dose. The attack rate was lower among the students who had received three doses than among those who had received two doses (6.7 vs. 14.5 cases per 1000 population, P<0.001). Students had more than nine times the risk of mumps if they had received the second MMR dose 13 years or more before the outbreak. At 28 days after vaccination, receipt of the third vaccine dose was associated with a 78.1% lower risk of mumps than receipt of a second dose (adjusted hazard ratio, 0.22; 95% confidence interval, 0.12 to 0.39). The vaccine effectiveness of two doses versus no doses was lower among students with more distant receipt of the second vaccine dose. CONCLUSIONS: Students who had received a third dose of MMR vaccine had a lower risk of mumps than did those who had received two doses, after adjustment for the number of years since the second dose. Students who had received a second dose of MMR vaccine 13 years or more before the outbreak had an increased risk of mumps. These findings suggest that the campaign to administer a third dose of MMR vaccine improved mumps outbreak control and that waning immunity probably contributed to propagation of the outbreak. (Funded by the Centers for Disease Control and Prevention.).

Assessing the potency and immunogenicity of inactivated poliovirus vaccine after exposure to freezing temperatures.

According to manufacturers, inactivated poliovirus vaccines (IPVs) are freeze sensitive and require storage between 2°C and 8°C, whereas oral poliovirus vaccine requires storage at -20 °C. Introducing IPV into ongoing immunization services might result in accidental exposure to freezing temperatures and potential loss of vaccine potency. To better understand the effect of freezing IPVs, samples of single-dose vaccine vials from Statens Serum Institut (VeroPol) and multi-dose vaccine vials from Sanofi Pasteur (IPOL) were exposed to freezing temperatures mimicking what a vaccine vial might encounter in the field. D-antigen content was measured to determine the in vitro potency by ELISA. Immunogenicity testing was conducted for a subset of exposed IPVs using the rat model. Freezing VeroPol had no detectable effect on in vitro potency (D-antigen content) in all exposures tested. Freezing of the IPOL vaccine for 7 days at -20 °C showed statistically significant decreases in D-antigen content by ELISA in poliovirus type 1 (p < 0.0001) and type 3 (p = 0.048). Reduction of poliovirus type 2 potency also approached significance (p = 0.062). The observed loss in D-antigen content did not affect immunogenicity in the rat model. Further work is required to determine the significance of the loss observed and the implications for vaccine handling policies and practices.

An acute flaccid paralysis surveillance-based serosurvey of poliovirus antibodies in Western Uttar Pradesh, India.

BACKGROUND: Despite intensified use of monovalent oral poliovirus type 1 vaccine and improved coverage of immunization campaigns, wild poliovirus type 1 persisted in Indian states of Uttar Pradesh and Bihar during 2006 to 2009. METHODS: A serosurvey was conducted among cases of acute flaccid paralysis in the 25 high-polio-incidence districts of western Uttar Pradesh. Children were recruited by age group (6-11 months, 12-24 months, and 25-69 months) from among cases reported through the acute flaccid paralysis surveillance system between November 2008 and August 2009. RESULTS: Seroprevalence for type 1 wild poliovirus was >96.4% for each age group. The seroprevalence of wild poliovirus types 2 and 3 increased with age, from 36.7% to 73.4% for type 2 and from 39.0% to 74.1% for type 3. In addition to the number of type-specific vaccine doses, father's level of education, being from a Muslim family, height for age, and female sex were the socioeconomic risk factors associated with seronegativity to poliovirus. CONCLUSIONS: The seroprevalence and risk factors identified in this study were consistent with the epidemiology of polio, and the findings were instrumental in optimizing vaccination strategy in western Uttar Pradesh with respect to the choice of OPV types, the frequency of supplementary immunization campaigns, and the urgency to improve routine immunization services.

Estimating the likely coverage of inactivated poliovirus vaccine in routine immunization: evidence from demographic and health surveys.

BACKGROUND: The Strategic Advisory Group of Experts on Immunization (SAGE) has recommended introduction of at least 1 dose of inactivated poliovirus vaccine (IPV) at ≥14 weeks of age through the routine immunization program in countries currently not using IPV. METHODS: We analyzed all available unrestricted data obtained from the Demographic and Health Surveys since 2005 in sub-Saharan Africa (31 countries) and in South and Southeast Asia (9 countries) to determine coverage of the following injectable vaccines delivered through the routine immunization schedule: diphtheria-tetanus-pertussis vaccine dose 1 (DTP1), DTP2, DTP3, and measles vaccine. Coverage with these vaccines was used as a proxy measure of likely 1- and 2-dose IPV coverage. RESULTS: Coverage with 1 dose of IPV is expected to be lowest when offered with DTP3 (median coverage, 73%) and highest when offered with DTP1 (median coverage, 90%). The median DTP1-DTP3 drop-out rate was 14%, which equates to an additional 12 million children not receiving IPV if IPV is offered with DTP3, rather than with DTP1. An increased geographical clustering of children who have not received IPV is expected in sub-Saharan Africa and Asia if IPV is offered with DTP3, rather than with DTP1. Coverage with 2 doses of IPV is expected to be lowest if IPV is administered with DTP3 and measles vaccine (69%) and highest if administered with DTP1 and DTP2 (84%). CONCLUSIONS: Coverage with 1 dose of IPV is expected to be lowest if it is administered at the DTP3 visit. At present, there is insufficient evidence to determine whether the SAGE-recommended IPV schedule for the polio endgame would maximize population immunity to type 2 poliovirus.

Assessing population immunity in a persistently high-risk area for wild poliovirus transmission in India: a serological study in Moradabad, Western Uttar Pradesh.

BACKGROUND: Moradabad district in Uttar Pradesh reported the highest number of paralytic polio cases in India during 2001-2007. We conducted a study in Moradabad in 2007 to assess seroprevalence against poliovirus types 1, 2, and 3 in children 6-12 and 36-59 months of age to guide future strategies to interrupt wild poliovirus transmission in high-risk areas. METHODS: Children attending 10 health facilities for minor illnesses who met criteria for study inclusion were eligible for enrollment. We recorded vaccination history, weight, and length and tested sera for neutralizing antibodies to poliovirus types 1, 2, and 3. RESULTS: Poliovirus type 1, 2, and 3 seroprevalences were 88% (95% confidence interval [CI], 84%-91%), 70% (95% CI, 66%-75%), and 75% (95% CI, 71%-79%), respectively, among 467 in the younger age group (n=467), compared with 100% (95% CI, 99%-100%), 97% (95% CI, 95%-98%), and 93% (91%-95%), respectively, among 447 children in the older age group (P<.001 for all serotypes). CONCLUSIONS: This seroprevalence study provided extremely useful information that was used by the program in India to guide immunization policies, such as optimizing the use of different OPV formulations in vaccination campaigns and strengthening routine immunization services. Similar surveys in populations at risk should be performed at regular intervals in countries where the risk of persistence or spread of indigenous or imported wild poliovirus is high.

Limited duration of vaccine poliovirus and other enterovirus excretion among human immunodeficiency virus infected children in Kenya.

BACKGROUND: Immunodeficient persons with persistent vaccine-related poliovirus infection may serve as a potential reservoir for reintroduction of polioviruses after wild poliovirus eradication, posing a risk of their further circulation in inadequately immunized populations. METHODS: To estimate the potential for vaccine-related poliovirus persistence among HIV-infected persons, we studied poliovirus excretion following vaccination among children at an orphanage in Kenya. For 12 months after national immunization days, we collected serial stool specimens from orphanage residents aged <5 years at enrollment and recorded their HIV status and demographic, clinical, immunological, and immunization data. To detect and characterize isolated polioviruses and non-polio enteroviruses (NPEV), we used viral culture, typing and intratypic differentiation of isolates by PCR, ELISA, and nucleic acid sequencing. Long-term persistence was defined as shedding for >or= 6 months. RESULTS: Twenty-four children (15 HIV-infected, 9 HIV-uninfected) were enrolled, and 255 specimens (170 from HIV-infected, 85 from HIV-uninfected) were collected. All HIV-infected children had mildly or moderately symptomatic HIV-disease and moderate-to-severe immunosuppression. Fifteen participants shed vaccine-related polioviruses, and 22 shed NPEV at some point during the study period. Of 46 poliovirus-positive specimens, 31 were from HIV-infected, and 15 from HIV-uninfected children. No participant shed polioviruses for >or= 6 months. Genomic sequencing of poliovirus isolates did not reveal any genetic evidence of long-term shedding. There was no long-term shedding of NPEV. CONCLUSION: The results indicate that mildly to moderately symptomatic HIV-infected children retain the ability to clear enteroviruses, including vaccine-related poliovirus. Larger studies are needed to confirm and generalize these findings.

Field Performance of Two Methods for Detection of Poliovirus in Wastewater Samples, Mexico 2016-2017.

To enhance our ability to monitor poliovirus circulation and certify eradication, we evaluated the performance of the bag-mediated filtration system (BMFS) against the two-phase separation (TPS) method for concentrating wastewater samples for poliovirus detection. Sequential samples were collected at two sites in Mexico; one L was collected by grab and ~ 5 L were collected and filtered in situ with the BMFS. In the laboratory, 500 mL collected by grab were concentrated using TPS and the sample contained in the filter of the BMFS was eluted without secondary concentration. Concentrates were tested for the presence of poliovirus and non-poliovirus enterovirus (NPEV) using Global Poliovirus Laboratory Network standard procedures. Between February 16, 2016, and April 18, 2017, 125 pairs of samples were obtained. Collectors spent an average (± standard deviation) of 4.3 ± 2.2 min collecting the TPS sample versus 73.5 ± 30.5 min collecting and filtering the BMFS sample. Laboratory processing required an estimated 5 h for concentration by TPS and 3.5 h for elution. Sabin 1 poliovirus was detected in 37 [30%] samples with the TPS versus 24 [19%] samples with the BMFS (McNemar's mid p value = 0.004). Sabin 3 poliovirus was detected in 59 [47%] versus 49 (39%) samples (p = 0.043), and NPEV was detected in 67 [54%] versus 40 [32%] samples (p < 0.001). The BMFS method without secondary concentration did not perform as well as the TPS method for detecting Sabin poliovirus and NPEV. Further studies are needed to guide the selection of cost-effective environmental surveillance methods for the polio endgame.

The risks, costs, and benefits of possible future global policies for managing polioviruses.

OBJECTIVES: We assessed the costs, risks, and benefits of possible future major policy decisions on vaccination, surveillance, response plans, and containment following global eradication of wild polioviruses. METHODS: We developed a decision analytic model to estimate the incremental cost-effectiveness ratios and net benefits of risk management options for polio for the 20-year period and stratified the world according to income level to capture important variability between nations. RESULTS: For low-, lower-middle-, and upper-middle-income groups currently using oral poliovirus vaccine (OPV), we found that after successful eradication of wild polioviruses, OPV cessation would save both costs and lives when compared with continued use of OPV without supplemental immunization activities. We found cost-effectiveness ratios for switching from OPV to inactivated poliovirus vaccine to be higher (i.e., less desirable) than other health investment opportunities, depending on the actual inactivated poliovirus vaccine costs and assumptions about whether supplemental immunization activities with OPV would continue. CONCLUSIONS: Eradication promises billions of dollars of net benefits, although global health policy leaders face difficult choices about future policies. Until successful eradication and coordination of posteradication policies, health authorities should continue routine polio vaccination and supplemental immunization activities.

Uncertainty and sensitivity analyses of a decision analytic model for posteradication polio risk management.

Decision analytic modeling of polio risk management policies after eradication may help inform decisionmakers about the quantitative tradeoffs implied by various options. Given the significant dynamic complexity and uncertainty involving posteradication decisions, this article aims to clarify the structure of a decision analytic model developed to help characterize the risks, costs, and benefits of various options for polio risk management after eradication of wild polioviruses and analyze the implications of different sources of uncertainty. We provide an influence diagram of the model with a description of each component, explore the impact of different assumptions about model inputs, and present probability distributions of model outputs. The results show that choices made about surveillance, response, and containment for different income groups and immunization policies play a major role in the expected final costs and polio cases. While the overall policy implications of the model remain robust to the variations of assumptions and input uncertainty we considered, the analyses suggest the need for policymakers to carefully consider tradeoffs and for further studies to address the most important knowledge gaps.

Immunogenicity of type 2 monovalent oral and inactivated poliovirus vaccines for type 2 poliovirus outbreak response: an open-label, randomised controlled trial.

BACKGROUND: Monovalent type 2 oral poliovirus vaccine (mOPV2) and inactivated poliovirus vaccine (IPV) are used to respond to type 2 poliovirus outbreaks. We aimed to assess the effect of two mOPV2 doses on the type 2 immune response by varying the time interval between mOPV2 doses and IPV co-administration with mOPV2. METHODS: We did a randomised, controlled, parallel, open-label, non-inferiority, inequality trial at two study clinics in Dhaka, Bangladesh. Healthy infants aged 6 weeks (42-48 days) at enrolment were randomly assigned (1:1:1:1) to receive two mOPV2 doses (each dose consisting of two drops [0·1 mL in total] of about 105 50% cell culture infectious dose of type 2 Sabin strain) at intervals of 1 week, 2 weeks, 4 weeks (standard or control group), or 4 weeks with IPV (0·5 mL of type 1 [Mahoney, 40 D-antigen units], type 2 [MEF-1, 8 D-antigen units], and type 3 [Saukett, 32 D-antigen units]) administered intramuscularly with the first mOPV2 dose. We used block randomisation, randomly selecting blocks of sizes four, eight, 12, or 16 stratified by study sites. We concealed randomisation assignment from staff managing participants in opaque, sequentially numbered, sealed envelopes. Parents and clinic staff were unmasked to assignment after the randomisation envelope was opened. Laboratory staff analysing sera were masked to assignment, but investigators analysing data and assessing outcomes were not. The primary outcome was type 2 immune response measured 4 weeks after mOPV2 administration. The primary modified intention-to-treat analysis included participants with testable serum samples before and after vaccination. A non-inferiority margin of 10% and p=0·05 (one-tailed) was used. This trial is registered at ClinicalTrials.gov, number NCT02643368, and is closed to accrual. FINDINGS: Between Dec 7, 2015, and Jan 5, 2016, we randomly assigned 760 infants to receive two mOPV2 doses at intervals of 1 week (n=191), 2 weeks (n=191), 4 weeks (n=188), or 4 weeks plus IPV (n=190). Immune responses after two mOPV2 doses were observed in 161 (93%) of 173 infants with testable serum samples in the 1 week group, 169 (96%) of 177 in the 2 week group, and 176 (97%) of 181 in the 4 week group. 1 week and 2 week intervals between two mOPV2 doses were non-inferior to 4 week intervals because the lower bound of the absolute differences in the percentage of immune responses were greater than -10% (-4·2% [90% CI -7·9 to -0·4] in the 1 week group and -1·8% [-5·0 to 1·5] in the 2 week group vs the 4 week group). The immune response elicited by two mOPV2 doses 4 weeks apart was not different when IPV was added to the first dose (176 [97%] of 182 infants with IPV vs 176 [97%] of 181 without IPV; p=1·0). During the trial, two serious adverse events (pneumonia; one [1%] of 186 patients in the 1 week group and one [1%] of 182 in the 4 week group) and no deaths were reported; the adverse events were not attributed to the vaccines. INTERPRETATION: Administration of mOPV2 at short intervals does not interfere with its immunogenicity. The addition of IPV to the first mOPV2 dose did not improve poliovirus type 2 immune response. FUNDING: US Centers for Disease Control and Prevention.

Use of the revised World Health Organization cluster survey methodology to classify measles-rubella vaccination campaign coverage in 47 counties in Kenya, 2016.

INTRODUCTION: To achieve measles elimination, two doses of measles-containing vaccine (MCV) are provided through routine immunization services or vaccination campaigns. In May 2016, Kenya conducted a measles-rubella (MR) vaccination campaign targeting 19 million children aged 9 months-14 years, with a goal of achieving ≥95% coverage. We conducted a post-campaign cluster survey to estimate national coverage and classify coverage in Kenya's 47 counties. METHODS: The stratified multi-stage cluster survey included data from 20,011 children in 8,253 households sampled using the recently revised World Health Organization coverage survey methodology (2015). Point estimates and 95% confidence intervals (95% CI) of national campaign coverage were calculated, accounting for study design. County vaccination coverage was classified as 'pass,' 'fail,' or 'intermediate,' using one-sided hypothesis tests against a 95% threshold. RESULTS: Estimated national MR campaign coverage was 95% (95% CI: 94%-96%). Coverage differed significantly (p < 0.05) by child's school attendance, mother's education, household wealth, and other factors. In classifying coverage, 20 counties passed (≥95%), two failed (<95%), and 25 were intermediate (unable to classify either way). Reported campaign awareness among caretakers was 92%. After the 2016 MR campaign, an estimated 93% (95% CI: 92%-94%) of children aged 9 months to 14 years had received ≥2 MCV doses; 6% (95% CI: 6%-7%) had 1 MCV dose; and 0.7% (95% CI: 0.6%-0.9%) remained unvaccinated. CONCLUSIONS: Kenya reached the MR campaign target of 95% vaccination coverage, representing a substantial achievement towards increasing population immunity. High campaign awareness reflected the comprehensive social mobilization strategy implemented in Kenya and supports the importance of including strong communications platforms in future vaccination campaigns. In counties with sub-optimal MR campaign coverage, further efforts are needed to increase MCV coverage to achieve the national goal of measles elimination by 2020.

The role of supplementary environmental surveillance to complement acute flaccid paralysis surveillance for wild poliovirus in Pakistan - 2011-2013.

BACKGROUND: More than 99% of poliovirus infections are non-paralytic and therefore, not detected by acute flaccid paralysis (AFP) surveillance. Environmental surveillance (ES) can detect circulating polioviruses from sewage without relying on clinical presentation. With extensive ES and continued circulation of polioviruses, Pakistan presents a unique opportunity to quantify the impact of ES as a supplement to AFP surveillance on overall completeness and timeliness of poliovirus detection. METHODS: Genetic, geographic and temporal data were obtained for all wild poliovirus (WPV) isolates detected in Pakistan from January 2011 through December 2013. We used viral genetics to assess gaps in AFP surveillance and ES as measured by detection of 'orphan viruses' (≥1.5% different in VP1 capsid nucleotide sequence). We compared preceding detection of closely related circulating isolates (≥99% identity) detected by AFP surveillance or ES to determine which surveillance system first detected circulation before the presentation of each polio case. FINDINGS: A total of 1,127 WPV isolates were detected by AFP surveillance and ES in Pakistan from 2011-2013. AFP surveillance and ES combined exhibited fewer gaps (i.e., % orphan viruses) in detection than AFP surveillance alone (3.3% vs. 7.7%, respectively). ES detected circulation before AFP surveillance in nearly 60% of polio cases (200 of 346). For polio cases reported from provinces conducting ES, ES detected circulation nearly four months sooner on average (117.6 days) than did AFP surveillance. INTERPRETATION: Our findings suggest ES in Pakistan is providing earlier, more sensitive detection of wild polioviruses than AFP surveillance alone. Overall, targeted ES through strategic selection of sites has important implications in the eradication endgame strategy.

Pathogen-Specific Burden of Outpatient Diarrhea in Infants in Nepal: A Multisite Prospective Case-Control Study.

BACKGROUND: Nonsevere diarrheal disease in Nepal represents a large burden of illness. Identification of the specific disease-causing pathogens will help target the appropriate control measures. METHODS: Infants aged 6 weeks to 12 months were recruited from 5 health facilities in eastern, central, and western Nepal between August 2012 and August 2013. The diarrhea arm included infants with mild or moderate diarrhea treatable in an outpatient setting; the nondiarrhea arm included healthy infants who presented for immunization visits or had a mild nondiarrheal illness. Stool samples were tested for 15 pathogens with a multiplex polymerase chain reaction (PCR) assay and real-time reverse-transcription (RT)-PCR assays for rotavirus and norovirus. Rotavirus- and norovirus-positive specimens were genotyped. We calculated attributable fractions (AFs) to estimate the pathogen-specific burden of diarrhea and adjusted for facility, age, stunting, wasting, and presence of other pathogens. RESULTS: We tested 307 diarrheal and 358 nondiarrheal specimens. Pathogens were detected more commonly in diarrheal specimens (164 of 307 [53.4%]) than in nondiarrheal specimens (113 of 358 [31.6%]) (P < .001). Rotavirus (AF, 23.9% [95% confidence interval (CI), 14.9%-32.8%]), Salmonella (AF, 12.4% [95% CI, 6.6%-17.8%]), and Campylobacter (AF, 5.6% [95% CI, 1.3%-9.8%]) contributed most to the burden of disease. In these diarrheal specimens, the most common genotypes for rotavirus were G12P[6] (27 of 82 [32.9%]) and G1P[8] (16 of 82 [19.5%]) and for norovirus were GII.4 Sydney (9 of 26 [34.6%]) and GII.7 (5 of 26 [19.2%]). CONCLUSIONS: The results of this study indicate that the introduction of a rotavirus vaccine in Nepal will likely decrease outpatient diarrheal disease burden in infants younger than 1 year, but interventions to detect and target other pathogens, such as Salmonella and Campylobacter spp, should also be considered.

Contribution of Contact Sampling in Increasing Sensitivity of Poliovirus Detection During A Polio Outbreak-Somalia, 2013.

Background. In May 2013, a wild poliovirus type 1 (WPV1) outbreak reported in Somalia provided an opportunity to examine the contribution of testing contacts to WPV detection. Methods. We reviewed acute flaccid paralysis (AFP) case-patients and linked contacts reported in the Somalia Surveillance Database from May 9 to December 31, 2013. We restricted our analysis to AFP case-patients that had ≥3 contacts and calculated the contribution of each contact to case detection. Results. Among 546 AFP cases identified, 328 AFP cases had ≥3 contacts. Among the 328 AFP cases with ≥3 contacts, 93 WPV1 cases were detected: 58 cases (62%; 95% confidence interval [CI], 52%-72%) were detected through testing stool specimens from AFP case-patients; and 35 cases (38%; 95% CI, 28%-48%) were detected through testing stool specimens from contacts, including 19 cases (20%; 95% CI, 14%-30%) from the first contact, 11 cases (12%; 95% CI, 7%-20%) from the second contact, and 5 cases (5%; 95% CI, 2%-12%) from the third contact. Among the 103 AFP cases with ≥4 contacts, 3 (6%; 95% CI, 2%-16%) of 52 WPV1 cases were detected by testing the fourth contact. No additional WPV1 cases were detected by testing >4 contacts. Conclusions. Stool specimens from 3 to 4 contacts of persons with AFP during polio outbreaks are needed to maximize detection of WPV cases.

The effect of diarrheal disease on bivalent oral polio vaccine (bOPV) immune response in infants in Nepal.

BACKGROUND: A globally-coordinated phase out of all type 2 containing oral polio vaccine (OPV) is planned for April 2016 during which bivalent 1+3 OPV (bOPV) will replace trivalent OPV (tOPV) in routine immunization schedules and campaigns. Diarrhea impairs the immune response to tOPV, but the effect of diarrhea on bOPV is unknown. METHODS: Infants aged 6 weeks to 11 months, who had received <3 doses of OPV and had mild-moderate diarrhea or no diarrhea, were recruited at five health facilities in Nepal. Neutralizing antibody titers to poliovirus types 1 and 3 were measured before and 28 days after bOPV administration. The effect of diarrhea and other factors on seroconversion or boosting in antibody titers to poliovirus was assessed by multivariable analysis. RESULTS: Infants with diarrhea, versus those without diarrhea, had reduced response for poliovirus types 1 (56% [87/156] vs 66% [109/164]) and 3 (34% [70/209] vs 52% [122/236]). After adjusting for other factors, infants with diarrhea had significantly reduced response for type 3 (odds ratio [OR]=0.44, 95% CI 0.29-0.68), as did infants with >5 loose stools per day (OR=0.36, 95% CI 0.21-0.62). CONCLUSIONS: Diarrhea reduced the immune response to bOPV. Provision of additional doses of polio vaccine is necessary to maintain high population immunity in areas with high prevalence of diarrheal disease. CLINICAL TRIAL REGISTRY: This study is registered at clinicaltrials.gov as NCT01559636.

Rubella immunity among pregnant women aged 15-44 years, Namibia, 2010.

BACKGROUND: The level of rubella susceptibility among women of reproductive age in Namibia is unknown. Documenting the risk of rubella will help estimate the potential burden of disease in Namibian women and the risk of congenital rubella syndrome (CRS) in infants, and will guide strategies for the introduction of rubella vaccine. METHODS: A total of 2044 serum samples from pregnant Namibian women aged 15-44 years were tested for rubella immunoglobulin G antibody; the samples were obtained during the 2010 National HIV Sentinel Survey. The proportion of women seropositive for rubella was determined by 5-year age strata, and factors associated with seropositivity were analyzed by logistic regression, including age, gravidity, HIV status, facility type, and urban/rural status. RESULTS: Overall rubella seroprevalence was 85% (95% confidence interval (CI) 83-86%). Seroprevalence varied by age group (83-90%) and health district (71-100%). In the multivariable model, women from urban residences had higher odds of seropositivity as compared to women from rural residences (odds ratio 1.40, 95% CI 1.09-1.81). CONCLUSIONS: In the absence of a routine rubella immunization program, the high level of rubella seropositivity suggests rubella virus transmission in Namibia, yet 15% of pregnant Namibian women remain susceptible to rubella. The introduction of rubella vaccine will help reduce the risk of rubella in pregnant women and CRS in infants.

Measles immunity among pregnant women aged 15-44 years in Namibia, 2008 and 2010.

BACKGROUND: Namibia experienced a large measles outbreak starting in 2009, with 38% of reported cases in adults, including women of reproductive age. Population immunity was assessed among pregnant women to determine whether immunization activities were needed in adults to achieve measles elimination in Namibia. METHODS: A total of 1708 and 2040 specimens sampled from Namibian pregnant women aged 15-44 years who were included in the 2008 and 2010 National HIV Sentinel Survey, respectively, were tested for measles immunoglobulin G antibody. The proportion of women seropositive overall and by 5-year age strata was determined, and factors associated with seropositivity were analyzed by logistic regression, including age, facility type, gravidity, HIV status, and urban/rural setting. Seropositivity in 2008 versus 2010 was compared. RESULTS: In both analysis years, measles seropositivity was lower in 15-19-year-olds (77%) and 20-24-year-olds (85-87%) and higher in 25-44-year-olds (90-94%) (2008, p<0.001; 2010, p<0.001). Overall measles seropositivity did not differ between 2008 (87%) and 2010 (87%) (p=0.7). HIV status did not affect seropositivity. CONCLUSIONS: Late in a large measles outbreak, 13% of pregnant women in Namibia, and almost one in four 15-19-year-old pregnant women, remained susceptible to measles. In Namibia, immunization campaigns with measles-containing vaccine should be considered for adults.

Environmental surveillance of wild poliovirus circulation in Egypt--balancing between detection sensitivity and workload.

Examination of sewage specimens for poliovirus (environmental surveillance) was adopted as a supplementary tool in the surveillance of poliomyelitis in Egypt. Sewage samples were concentrated about 50-fold using a simple two-phase separation technique, and inoculated in cell cultures in two collaborating laboratories in parallel. All but 9 of the 293 (97%) samples collected from January 2001 to December 2002 contained poliovirus and/or other enteroviruses, with polioviruses being detected in 84% of the samples. The proportion of specimens containing type 1 wild poliovirus (PV1W, the North-East African (NEAF) genotype) was less in 2002 (16%) than in 2001 (57%), and further decreased in 2003. While the overall sensitivity to detect PV1W was similar in the two collaborating laboratories, the specimens scored positive were not identical. Parallel cultures inoculated with aliquots of a given specimen very frequently resulted in isolation of different viruses. Moreover, partial sequence analysis occasionally revealed representatives of different genetic lineages of PV1W in a given specimen. These results emphasize the need to use intensive laboratory analysis to optimise sample sensitivity in environmental poliovirus surveillance, and the difficulties in reproducing the isolation results by simple re-inoculation of samples containing a mixture of different viruses.

Effect of time at temperature on wild poliovirus titers in stool specimens.

BACKGROUND: The effect of transport temperature on the viability of poliovirus in stool specimens from paralyzed cases has not been tested. Quality assurance of programmatic indicators will be necessary in the final phase of polio eradication. OBJECTIVE: To estimate the effect of time at elevated temperatures on wild poliovirus titers in stool specimens. METHODS: We exposed aliquots of pooled wild poliovirus type 1 specimens to elevated temperatures (27 °C, 31 °C, and 35 °C) for varying time periods up to 14 days. We determined the virus titer of these aliquots and created decay curves at each temperature to estimate the relationship between time at temperature and virus titer. RESULTS: We found significantly different slopes of decay at each temperature. The negative slopes increased as the temperature increased. CONCLUSIONS: While poliovirus in stool remains relatively stable at moderately elevated temperature, transport at higher temperatures could impact sample integrity and virus isolation results.

Early priming with inactivated poliovirus vaccine (IPV) and intradermal fractional dose IPV administered by a microneedle device: A randomized controlled trial.

INTRODUCTION: Inactivated poliovirus vaccine (IPV) introduction and phased oral poliovirus vaccine (OPV) cessation are essential for eradication of polio. METHODS: Healthy 6-week old infants in Bangladesh were randomized to one of five study arms: receipt of trivalent OPV (tOPV) or bivalent OPV (bOPV) at ages 6, 10 and 14 weeks, intramuscular IPV or intradermal one-fifth fractional dose IPV (f-IPV) at ages 6 and 14 weeks, or f-IPV at ages 6 and 14 weeks with bOPV at age 10 weeks (f-IPV/bOPV). All participants received tOPV at age 18 weeks. RESULTS: Of 975 infants randomized, 95% (922) completed follow-up. Type 1 seroconversion after 3 doses at 6, 10 and 14 weeks was higher with bOPV compared with tOPV (99% vs 94%, p=0.019). Seroconversions to types 1 and 3 after 2 IPV doses at ages 6 and 14 weeks were no different than after 3 doses of tOPV or bOPV at ages 6, 10 and 14 weeks. A priming response, seroconversion 1 week after IPV at 14 weeks among those who did not seroconvert after IPV at 6 weeks, was observed against poliovirus types 1, 2 and 3 in 91%, 84% and 97%, respectively. Compared with IPV, f-IPV failed non-inferiority tests for seroconversion with 1 or 2 doses and priming after 1 dose. DISCUSSION: The findings demonstrate considerable priming with IPV at age 6 weeks, comparable immunogenicity of tOPV and bOPV, and inferior immunogenicity of one-fifth f-IPV compared with IPV. If IPV induced priming at age 6 weeks is similar to that at age 14 weeks, IPV could be administered at a younger age and possibly with a higher coverage.