Increased Population Prevalence of Low Pertussis Toxin Antibody Levels in Young Children Preceding a Record Pertussis Epidemic in Australia

Background: Cross-sectional serosurveys using IgG antibody to pertussis toxin (IgG-PT) are increasingly being used to estimate trends in recent infection independent of reporting biases. Methods/Principal Findings: We compared the age-specific seroprevalence of various levels of IgG-PT in cross-sectional surveys using systematic collections of residual sera from Australian diagnostic laboratories in 1997/8, 2002 and 2007 with reference to both changes in the pertussis vaccine schedule and the epidemic cycle, as measured by disease notifications. A progressive decline in high-level ($62.5 EU/ml) IgG-PT prevalence from 19 % (95 % CI 16–22%) in 1997/98 to 12 % (95 % CI 11–14%) in 2002 and 5 % (95 % CI 4–6%) in 2007 was consistent with patterns of pertussis notifications in the year prior to each collection. Concomitantly, the overall prevalence of undetectable (,5 EU/ml) levels increased from 17 % (95 % CI 14– 20%) in 1997/98 to 38 % (95 % CI 36–40%) in 2007 but among children aged 1–4 years, from 25 % (95 % CI 17–34%) in 1997/98 to 62 % (95 % CI 56–68%) in 2007. This change followed withdrawal of the 18-month booster dose in 2003 and preceded record pertussis notifications from 2008 onwards. Conclusions/Significance: Population seroprevalence of high levels of IgG-PT is accepted as a reliable indicator of pertussis disease activity over time within and between countries with varying diagnostic practices, especially in unimmunised age groups. Our novel findings suggest that increased prevalence of undetectable IgG-PT is an indicator of waning immunit

Measuring underreporting and under-ascertainment in infectious disease datasets: a comparison of methods

Gibbons CL, Mangen M-JJ, Plaß D, et al. Measuring underreporting and under-ascertainment in infectious disease datasets: a comparison of methods. BMC Public Health. 2014;14(1): 147.Background: Efficient and reliable surveillance and notification systems are vital for monitoring public health and disease outbreaks. However, most surveillance and notification systems are affected by a degree of underestimation (UE) and therefore uncertainty surrounds the 'true' incidence of disease affecting morbidity and mortality rates. Surveillance systems fail to capture cases at two distinct levels of the surveillance pyramid: from the community since not all cases seek healthcare (under-ascertainment), and at the healthcare-level, representing a failure to adequately report symptomatic cases that have sought medical advice (underreporting). There are several methods to estimate the extent of under-ascertainment and underreporting. Methods: Within the context of the ECDC-funded Burden of Communicable Diseases in Europe (BCoDE)-project, an extensive literature review was conducted to identify studies that estimate ascertainment or reporting rates for salmonellosis and campylobacteriosis in European Union Member States (MS) plus European Free Trade Area (EFTA) countries Iceland, Norway and Switzerland and four other OECD countries (USA, Canada, Australia and Japan). Multiplication factors (MFs), a measure of the magnitude of underestimation, were taken directly from the literature or derived (where the proportion of underestimated, under-ascertained, or underreported cases was known) and compared for the two pathogens. Results: MFs varied between and within diseases and countries, representing a need to carefully select the most appropriate MFs and methods for calculating them. The most appropriate MFs are often disease-,country-, age-, and sex-specific. Conclusions: When routine data are used to make decisions on resource allocation or to estimate epidemiological parameters in populations, it becomes important to understand when, where and to what extent these data represent the true picture of disease, and in some instances (such as priority setting) it is necessary to adjust for underestimation. MFs can be used to adjust notification and surveillance data to provide more realistic estimates of incidence

Prevalence of hepatitis and HIV infections and vaccination rates in patients entering the heroin-assisted treatment in Switzerland between 1994 and 2002

Background: Hepatitis C virus (HCV) remains very prevalent in injection drug users (IDUs). In spite of recommended vaccinations against hepatitis A virus (HAV) and hepatitis B virus (HBV), many IDUs remain susceptible to HAV and HBV. Study population and methods: Patients entering heroin-assisted treatment between 2000 and 2002 (N = 210) were compared for infectious disease status with patients entering this treatment in 1998 (N = 243) and between 1994 and 1996 (N = 1035). Infection status was determined with the aid of questionnaires and blood tests for antibodies against HAV, HBV core antigen, HCV and HIV. Results: In the cohort 2000–2002 78.3% of the patients were HCV positive, 53.3% were HBV positive, 41.2% were HAV positive and 12.6% were HIV positive. In comparison to the cohorts entering the heroin- assisted treatment at an earlier time, there was a significant reduction of HBV and HAV infections, but not of HCV and HIV infections. 15.6% of the patients entering between 2000 and 2002 were vaccinated against HBV and 10.3% against HAV. 31.1% of patients at entrance were susceptible for HBV and 48.5% for HAV. In comparison to patients entering treatment in 1998 there was no significant increase in patients who were vaccinated against HBV. Conclusions: This data illustrates the need for improving HCV prevention and more consequent vaccination against HBV and HAV in IDUs