Clinical characteristics and risk factors associated with breakthrough varicella during varicella outbreaks.

BACKGROUND: Although a varicella vaccine has been available in China since 1998 in the private sector, varicella outbreaks and breakthrough varicella (BV) still occur. In 2018, four varicella outbreaks with high BV rate sequentially occurred in four schools in Lu'an, sparking local public health authority's concerns on the varicella vaccine. Therefore, we conducted this investigation to evaluate varicella vaccine effectiveness (VE), characterize BV, and detect potential risk factors associated with BV. METHODS: This was a three-stage study. First, a retrospective cohort study was done in each school to estimate the VEs of varicella vaccine  during outbreaks. Second, a descriptive epidemiological method was used to describe the characteristics of the four outbreaks and to compare the clinical characteristics between the BV cases and unvaccinated varicella cases. To identify the risk factors associated with BV, we conducted an unmatched case-control study in the third stage of the study. RESULTS: A total of 199 cases were identified among four outbreaks, and the overall attack rate was 14%. Of 1203 students with available vaccination information, 822 (68%) were vaccinated at least once. The overall VEs among four outbreaks ranged from 19% to 69%, whereas the VE against moderate or severe varicella ranged from 74% to 90%. Compared with unvaccinated varicella cases, the moderate or severe varicella (p < .001) and fever (p = .029) in the BV group were less common. Besides, BV cases had a shorter duration of disease (p = .007). Children vaccinated more than six years before the outbreak had a higher risk of developing BV compared with those vaccinated within the past six years (OR = 2.4, 95% CI: 1.2-4.8). The risk of developing BV differed by the exposure intensity. Compared with the presence of three or fewer varicella cases in the same class, the OR was 7.8 (95% CI: 3.6-16.9) for four to nine cases in the same class and 25.2 (95% CI: 13.5 -47.2) for that of 10 or more cases. CONCLUSIONS: The overall VE was insufficient to protect varicella infection, and the VE for moderate or severe varicella was only moderate. The manifestations of BV cases were generally milder than those seen in natural varicella infection. The time since vaccination and the intensity of exposure are risk factors for developing BV during an outbreak.

Seroprevalence and risk factors of severe fever with thrombocytopenia syndrome virus infection in endemic areas.

BACKGROUND: To determine the seroprevalence, latent infection rate and risk factors for severe fever with thrombocytopenia syndrome virus (SFTSV) infection, a cross-sectional study was conducted in the general population of the Western region of Anhui Province of China from 1 September to 31 December 2014. METHODS: Twelve villages with the highest rates of endemic SFTS infection were selected from six towns in two counties in the western region of Anhui Province. Blood samples were collected and tested for the presence of SFTSV-IgG antibodies by ELISA. Each participant was interviewed using a structured questionnaire before blood collection. Participants with seropositive specimens were further investigated using another structured questionnaire. RESULTS: Of 2126 blood specimens collected, 99 (4.66%) were seropositive for SFTSV. None of the participants had been diagnosed with SFTS before the blood collection or were accompanied by fever, thrombocytopenia and leukocytopenia after blood collection. Multivariate logistic regression model analysis revealed living in areas of uncontrolled vegetation growth, long-term residents of the locality and tick bites as high risk factors for SFTSV infection. CONCLUSIONS: The overall seroprevalence of SFTSV is higher in the western region of Anhui, possibly due to latent infection, with the main risk factors being living in areas of uncontrolled vegetation growth, long-term residents of the locality and tick bites. Further investigations are warranted to clarify the modes of SFTS virus transmission, while vector management, education on tick bite prevention and personal hygiene management should be implemented for high risk groups in endemic areas.

A comparison of item response theory-based methods for examining differential item functioning in object naming test by language of assessment among older Latinos.

Object naming tests are commonly included in neuropsychological test batteries. Differential item functioning (DIF) in these tests due to cultural and language differences may compromise the validity of cognitive measures in diverse populations. We evaluated 26 object naming items for DIF due to Spanish and English language translations among Latinos (n=1,159), mean age of 70.5 years old (Standard Deviation (SD)±7.2), using the following four item response theory-based approaches: Mplus/Multiple Indicator, Multiple Causes (Mplus/MIMIC; Muthén & Muthén, 1998-2011), Item Response Theory Likelihood Ratio Differential Item Functioning (IRTLRDIF/MULTILOG; Thissen, 1991, 2001), difwithpar/Parscale (Crane, Gibbons, Jolley, & van Belle, 2006; Muraki & Bock, 2003), and Differential Functioning of Items and Tests/MULTILOG (DFIT/MULTILOG; Flowers, Oshima, & Raju, 1999; Thissen, 1991). Overall, there was moderate to near perfect agreement across methods. Fourteen items were found to exhibit DIF and 5 items observed consistently across all methods, which were more likely to be answered correctly by individuals tested in Spanish after controlling for overall ability.