Jennifer Zipprich

California Pertussis Epidemic, 2010

OBJECTIVE In 2010, California experienced the highest number of pertussis cases in >60 years, with >9000 cases, 809 hospitalizations, and 10 deaths. This report provides a descriptive epidemiologic analysis of this epidemic and describes public health mitigation strategies that were used, including expanded pertussis vaccine recommendations. STUDY DESIGN Clinical and demographic information were evaluated for all pertussis cases with onset from January 1, 2010, through December 31, 2010, and reported to the California Department of Public Health. RESULTS Hispanic infants younger than 6 months had the highest disease rates; all deaths and most hospitalizations occurred in infants younger than 3 months. Most pediatric cases were vaccinated according to national recommendations, although 9% of those aged 6 months to 18 years were completely unvaccinated against pertussis. High disease rates also were observed in fully vaccinated preadolescents, especially 10-year-olds. Mitigation strategies included expanded tetanus, diphtheria, and acellular pertussis vaccine recommendations, public and provider education, distribution of free vaccine for postpartum women and contacts of infants, and clinical guidance on diagnosis and treatment of pertussis in young infants. CONCLUSIONS Infants too young to be fully vaccinated against pertussis remain at highest risk of severe disease and death. Data are needed to evaluate strategies offering direct protection of this vulnerable population, such as immunization of pregnant women and of newborns. The high rate of disease among preadolescents suggests waning of immunity from the diphtheria, tetanus, and acellular pertussis series; additional studies are warranted to evaluate the efficacy and duration of protection of the diphtheria, tetanus, and acellular pertussis series and the tetanus, diphtheria, and acellular pertussis series.

Nonmedical Vaccine Exemptions and Pertussis in California, 2010

BACKGROUND: In 2010, 9120 cases of pertussis were reported in California, more than any year since 1947. Although this resurgence has been widely attributed to waning immunity of the acellular vaccine, the role of vaccine refusal has not been explored in the published literature. Many factors likely contributed to the outbreak, including the cyclical nature of pertussis, improved diagnosis, and waning immunity; however, it is important to understand if clustering of unvaccinated individuals also played a role. METHODS: We analyzed nonmedical exemptions (NMEs) for children entering kindergarten from 2005 through 2010 and pertussis cases with onset in 2010 in California to determine if NMEs increased in that period, if children obtaining NMEs clustered spatially, if pertussis cases clustered spatially and temporally, and if there was statistically significant overlap between clusters of NMEs and cases. RESULTS: Kulldorff’s scan statistics identified 39 statistically significant clusters of high NME rates and 2 statistically significant clusters of pertussis cases in this time period. Census tracts within an exemptions cluster were 2.5 times more likely to be in a pertussis cluster (odds ratio = 2.47, 95% confidence interval: 2.22–2.75). More cases occurred within as compared with outside exemptions clusters (incident rate ratios = 1.20, 95% confidence interval: 1.10–1.30). The association remained significant after adjustment for demographic factors. NMEs clustered spatially and were associated with clusters of pertussis cases. CONCLUSIONS: Our data suggest clustering of NMEs may have been 1 of several factors in the 2010 California pertussis resurgence.

Risk Factors Associated With Infant Deaths From Pertussis: A Case-Control Study

BACKGROUND In the current era, most pertussis deaths occur in infants <3 months of age. Leukocytosis with lymphocytosis and pneumonia are commonly observed among cases of severe pertussis. METHODS Risk factors associated with fatal pertussis were identified by comparing fatal pertussis cases among patients <120 days of age occurring from 1 January 1998 through 26 December 2014, matched by age (<120 days), county of residence, and closest symptom onset date with 1-4 nonfatal hospitalized cases. California Department of Public Health surveillance data were reviewed to identify cases; demographics, clinical presentation, and course were abstracted from corresponding birth and medical records. Logistic regression and classification tree analyses were used to examine the risk of fatal pertussis with respect to identified factors. RESULTS Fifty-three fatal infant pertussis cases were identified and compared with 183 nonfatal hospitalized pertussis cases. Fatal cases had significantly lower birth weight, younger gestational age, younger age at time of cough onset, and higher peak white blood cell (WBC) and lymphocyte counts. Fatal cases were less likely to have received macrolide antibiotics and more likely to have received steroids or nitric oxide and to develop pulmonary hypertension, seizures, encephalitis, and pneumonia. Additionally, exchange transfusion, extracorporeal membrane oxygenation, and intubation occurred significantly more frequently among fatal cases. In multivariate analyses, peak WBC count, birth weight, intubation, and receipt of nitric oxide were predictors of death. CONCLUSIONS Early recognition of pertussis in young infants and treatment with appropriate antibiotic therapy are important in preventing death. Several risk factors are strongly associated with fatal pertussis in infants.

Effectiveness of a school district closure for pandemic influenza A (H1N1) on acute respiratory illnesses in the community: a natural experiment

BACKGROUND Following detection of pandemic influenza A H1N1 (pH1N1) in Dallas/Fort Worth, Texas, a school district (intervention community, [IC]) closed all public schools for 8 days to reduce transmission. Nearby school districts (control community [CC]) mostly remained open. METHODS We collected household data to measure self-reported acute respiratory illness (ARI), before, during, and after school closures. We also collected influenza-related visits to emergency departments (ED(flu)). RESULTS In both communities, self-reported ARIs and ED(flu) visits increased from before to during the school closure, but the increase in ARI rates was 45% lower in the IC (0.6% before to 1.2% during) than in the CC (0.4% before to 1.5% during) (RRR(During)(/Before) = 0.55, P < .001; adjusted OR(During/Before) = 0.49, P < .03). For households with school-aged children only (no children 0-5 years), IC had even lower increases in adjusted ARI than in the CC (adjusted OR(During/Before) = 0.28, P < .001). The relative increase of total ED(flu) visits in the IC was 27% lower (2.8% before to 4.4% during) compared with the CC (2.9% before to 6.2% during). Among children aged 6-18 years, the percentage of ED(flu) in IC remained constant (5.1% before vs 5.2% during), whereas in the CC it more than doubled (5.2% before vs 10.9% during). After schools reopened, ARI rates and ED(flu) visits decreased in both communities. CONCLUSIONS Our study documents a reduction in ARI and ED(flu) visits in the intervention community. Our findings can be used to assess the potential benefit of school closures during pandemics.

Notes from the Field: Outbreak of Serogroup B Meningococcal Disease at a University — California, 2016

On January 31, 2016, the Santa Clara County Public Health Department (SCCPHD) was notified of a suspected case of meningococcal disease in a university undergraduate student. By February 2, two additional suspected cases had been reported in undergraduate students living on the same campus. The index patient (patient A) required intensive care, whereas patients B and C had milder illness; there were no deaths. All three patients were part of overlapping social networks and had attended the same events during the week before the onset of patient As symptoms, but whether they had direct contact with one another could not be verified. Serogroup B Neisseria meningitidis was identified in cerebrospinal fluid and blood from patient A and in blood from patient B. Serogroup B has been responsible for all U.S. college outbreaks of meningococcal disease since 2011 (1). Laboratory results for patient C were inconclusive.

Impact of the US Two-dose Varicella Vaccination Program on the Epidemiology of Varicella Outbreaks: Data from Nine States, 2005-2012.

Background: A routine 2-dose varicella vaccination program was adopted in 2007 in the US to help further decrease varicella disease and prevent varicella outbreaks. We describe trends and characteristics of varicella outbreaks reported to the Centers for Disease Control and Prevention (CDC) during 2005–2012 from 9 states. Methods: Data on varicella outbreaks collected by 9 state health departments were submitted to CDC using the CDC outbreak reporting worksheet. Information was collected on dates of the outbreak, outbreak setting and number of cases by outbreak; aggregate data were provided on the numbers of outbreak-related cases by age group, vaccination status and laboratory confirmation. Results: Nine hundred and twenty-nine outbreaks were reported from the 6 states, which provided data for each year during 2005–2012. Based on data from these 6 states, the number of outbreaks declined by 78%, decreasing from 147 in 2005 to 33 outbreaks in 2012 (P = 0.0001). There were a total of 1015 varicella outbreaks involving 13,595 cases reported by the 9 states from 2005 to 2012. The size and duration of outbreaks declined significantly over time (P < 0.001). The median size of outbreaks was 12, 9 and 7 cases and median duration of outbreaks was 38, 35 and 26 days during 2005–2006, 2007–2009 and 2010–2012, respectively. Majority of outbreaks (95%) were reported from schools, declining from 97% in 2005–2006 to 89% in 2010–2012. Sixty-five percent of outbreak-related cases occurred among 5-year to 9-year olds, with the proportion declining from 76% in 2005–2006 to 45% during 2010–2012. Conclusions: The routine 2-dose varicella vaccination program appears to have significantly reduced the number, size and duration of varicella outbreaks in the US.

The Effect of Contact Investigations and Public Health Interventions in the Control and Prevention of Measles Transmission: A Simulation Study

Background Measles cases continue to occur despite its elimination status in the United States. To control transmission, public health officials confirm the measles diagnosis, identify close contacts of infectious cases, deliver public health interventions (i.e., post-exposure prophylaxis) among those who are eligible, and follow-up with the close contacts to determine overall health outcomes. A stochastic network simulation of measles contact tracing was conducted using existing agent-based modeling software and a synthetic population with high levels of immunity in order to estimate the impact of different interventions in controlling measles transmission. Methods and Findings The synthetic population was created to simulate California`s population in terms of population demographics, household, workplace, school, and neighborhood characteristics using California Department of Finance 2010 census data. Parameters for the model were obtained from a review of the literature, California measles case surveillance data, and expert opinion. Eight different scenarios defined by the use of three different public health interventions were evaluated: (a) post-exposure measles, mumps, and rubella (MMR) vaccine, (b) post-exposure immune globulin (IG), and (c) voluntary isolation and home quarantine in the presence or absence of public health response delays. Voluntary isolation and home quarantine coupled with one or two other interventions had the greatest reduction in the number of secondary cases infected by the index case and the probability of escape situations (i.e., the outbreak continues after 90 days). Conclusions Interrupting contact patterns via voluntary isolation and home quarantine are particularly important in reducing the number of secondary cases infected by the index case and the probability of uncontrolled outbreaks.

Perinatal transmission in infants of mothers with chronic hepatitis B in California

AIM To evaluate maternal hepatitis B virus (HBV) DNA as risk for perinatal HBV infection among infants of HBV-infected women in California. METHODS Retrospective analysis among infants born to hepatitis B surface antigen (HBsAg)-positive mothers who received post vaccination serologic testing (PVST) between 2005 and 2011 in California. Demographic information was collected from the California Department of Public Health Perinatal Hepatitis B Program databaseand matched to birth certificate records. HBV DNA level and hepatitis B e antigen (HBeAg) status were obtained from three large commercial laboratories in California and provider records if available and matched to mother infant pairs. Univariate analysis compared infected and uninfected infants. Multivariate analysis was restricted to infected infants and controls with complete maternal HBV DNA results using a predefined high HBV DNA level of > 2 × 107 IU/mL, a 5:1 ratio of cases to controls and a two-sided confidence level of 95%. RESULTS A total of 17687 infants were born to HBsAg positive mothers in California between Jan 1 2005 and Dec 31, 2011. Among 11473 infants with PVST, only 125 (1.1%) were found to be HBV infected. Among these infected infants, lapses in Advisory Committee on Immunization Practices recommended post exposure prophylaxis (PEP) occurred in only 9 infants. However, PEP errors were not significantly different between infected and uninfected infants. Among the 347 uninfected and infected infants who had maternal HBeAg and HBV DNA level, case-control analysis found HBeAg positivity (70.4% vs 28.9%, OR = 46.76, 95%CI: 6.05-361.32, P < 0.001) and a maternal HBV DNA level ≥ 2 × 107 IU/mL (92.6% vs 18.5%, OR = 54.5, 95%CI: 12.22-247.55, P < 0.001) were associated with perinatal HBV infection. In multivariate logistic regression, maternal HBV DNA level ≥ 2 × 107 IU/mL was the only significant independent predictor of perinatal HBV infection. CONCLUSION In California, transmission is low and most infected infants receive appropriate PEP and vaccination. Maternal HBV DNA ≥ 2 × 107 IU/mL is associated with high risk of perinatal infection.

Clinical Characteristics and Factors Associated With Measles Transmission in California

Background. Since 2014, California has experienced an increase in measles cases including a large outbreak associated with a theme park. We describe factors associated with measles transmission and clinical features of cases with ≥2 doses of MCV. Method. Measles cases reported to the California Department of Public Health (CDPH) from January 1, 2000–July 1, 2015 were reviewed. Measles transmitters were defined as patients who transmitted measles to one or more persons based on epidemiologic linkage, supported by appropriate timing and genotype data, when available. Ambiguous exposure situations were excluded. Multiple logistic regression was used to identify factors associated with measles transmission, including measles clinical features (cough, coryza, conjunctivitis, fever), vaccination status and age. Fishers exact test was used in a sub-analysis of clinical features among those with verified immunization status. Result. Three hundred ninety-seven measles cases were reported to CDPH. In the multiple logistic regression model, coughing increased odds of transmission (OR: 3.3; 95% CI: 1.1–9.7), whereas age 2 doses of MCV. In a sub-analysis of those with documented vaccination status, cases with ≥2 MCV doses less frequently reported cough (p < 0.0001), coryza (p < 0.0001), conjunctivitis (p < 0.0001), fever (p < 0.01) and hospitalization (p = 0.03) versus unvaccinated cases or those with one dose. The median time since vaccination for cases with ≥2 MCV doses was 17 years (range: 6–39 years). Three patients with ≥2 MCV doses transmitted measles to close contacts; all reported cough while none of the patients with ≥2 MCV doses but without cough transmitted. Conclusion. Clinical and demographic features may be used to identify cases at high risk of transmitting measles and to prioritize investigation of their contacts. Prior vaccination appears to attenuate measles illness and reduce transmission. While some cases with ≥2 MCV doses are primary vaccine failures, the role of waning immunity among vaccinated people in measles outbreaks should be considered. Disclosures. J. Zipprich, Pfizer: Spouse works at Pfizer, Salary; J. D. Cherry, Global Pertussis Initiative: Member, Honoraria for participating and speaking at many GPI meetings since 2000. Sanofipasteur: Speakers Bureau, Speaker honorarium