Population-based Seroprevalence Study Research Articles

Challenges to mapping the health risk of hepatitis A virus infection

BackgroundWorld maps are among the most effective ways to convey public health messages such as recommended vaccinations, but creating a useful and valid map requires careful deliberation. The changing epidemiology of hepatitis A virus (HAV) in many world regions heightens the need for up-to-date risk maps. HAV infection is usually asymptomatic in children, so low-income areas with high incidence rates usually have a low burden of disease. In higher-income areas, many adults remain susceptible to the virus and, if infected, often experience severe disease.ResultsSeveral challenges associated with presenting hepatitis A risk using maps were identified, including the need to decide whether prior infection or continued susceptibility more aptly indicates risk, whether to display incidence or prevalence, how to distinguish between different levels of risk, how to display changes in risk over time, how to present complex information to target audiences, and how to handle missing or obsolete data.ConclusionFor future maps to be comparable across place and time, we propose the use of the age at midpoint of population susceptibility as a standard indicator for the level of hepatitis A endemicity within a world region. We also call for the creation of an accessible active database for population-based age-specific HAV seroprevalence and incidence studies. Health risk maps for other conditions with rapidly changing epidemiology would benefit from similar strategies.

Seroprevalence of Human Papillomavirus Types 6, 11, 16, and 18 in the United States: National Health and Nutrition Examination Survey 2003–2004

Human papillomavirus (HPV) seroprevalence data can help define the epidemiology of this common sexually transmitted pathogen. We determined the seroprevalence of HPV types 6, 11, 16, and 18 (HPV types in the quadrivalent vaccine) among 4303 persons aged 14-59 years who participated in the National Health and Nutrition Examination Survey 2003-2004. The seroprevalences of HPV types 6, 11, 16, and 18 among female subjects were 17.0%, 7.1%, 15.6%, and 6.5%, respectively. Among males, the seroprevalences were lower for each type, with 6.3% observed for HPV-6, 2.0% for HPV-11, 5.1% for HPV-16, and 1.5% for HPV-18 (P < .001 for all comparisons). For any HPV vaccine type, the seroprevalence was 32.5% among females and 12.2% among males; the seroprevalence of any HPV vaccine type increased with age, reaching 42.0% among women aged 30-39 years and 18.0% among men aged 50-59 years. Antibodies to all 4 vaccine types were detected in 0.4% of females and 0% of males. Non-Hispanic blacks had a higher seroprevalence of any HPV vaccine type than that observed for non-Hispanic whites or Mexican Americans. Age and lifetime number of sex partners were factors independently associated with seroprevalence of any HPV vaccine type among both females and males, and poverty level was also a factor among females. This is the first population-based seroprevalence study in the United States of all 4 HPV types targeted by the quadrivalent vaccine, and its findings can inform vaccine policy.

The epidemiology of Varicella Zoster Virus infection in Italy

BackgroundThe epidemiological importance of varicella and zoster and the availability of an efficacious and safe vaccine have led to an important international debate regarding the suitability of mass vaccination. The objective of the study was to describe the epidemiology of varicella and zoster in Italy and to determine whether there have been changes with respect to observations provided by an analogous study conducted 8 years ago, in order to define the most appropriate vaccination strategy.MethodsA number of data sources were evaluated, a cross-sectional population-based seroprevalence study was conducted on samples collected in 2004, and the results were compared with data obtained in 1996.ResultsThe data from active and passive surveillance systems confirm that varicella is a widespread infectious disease which mainly affects children. VZV seroprevalence did not substantially differ from that found in the previous study. The sero-epidemiological profile in Italy is different from that in other European countries. In particular, the percentage of susceptible adolescents is at least nearly twice as high as in other European countries and in the age group 20–39 yrs, approximately 9% of individuals are susceptible to VZV.ConclusionThe results of this study can contribute to evaluating the options for varicella vaccination. It is possible that in a few years, in all Italian Regions, there will exist the conditions necessary for implementing a mass vaccination campaign and that the large-scale availability of MMRV tetravalent vaccines will facilitate mass vaccination.

Rubella seroprofile of the Italian population: an 8-year comparison

The objective of this study is to evaluate how increasing MMR infant vaccination coverage in recent years has modified the epidemiology of rubella in Italy. A cross-sectional population-based seroprevalence study of rubella antibodies was conducted on 3094 sera, in 2004, and results were compared with data obtained by the same method in 1996. The overall proportion of rubella-seropositive individuals was found to be significantly higher in 2004 with respect to 1996 (84.6% vs. 77.4%). However, an increase in seropositivity was observed only in the 1-19 years age groups. Recent increases in childhood MMR vaccination coverage, therefore, have not had an impact on seroprevalence in women of childbearing age, over 5% of whom remain susceptible to rubella. Preconception screening and postpartum vaccination of susceptible women are fundamental if the WHO target of less than one case of congenital rubella syndrome per 100,000 live births is to be attained.

Population-based Toxoplasma seroprevalence study in The Netherlands.

During 1995--1996 a population-based seroprevalence study was conducted in The Netherlands. Risk factors were established for postnatally acquired toxoplasmosis. The results were compared with a study conducted during 1987-1988 in pregnant women in the Southwest of The Netherlands in order to estimate the change in seroprevalence. In total, 7521 sera were tested and the national seroprevalence was 40.5 % (95 % CI 37.5-43.4). Living in the Northwest, having professional contact with animals, living in a moderately urbanized area, being divorced or widowed, being born outside The Netherlands, frequent gardening and owning a cat were independently associated with Toxoplasma seropositivity. Risk factors like eating undercooked meat could not be studied. The seroprevalence among women aged 15-49 years was 10 % lower (35.2 %, 95 % CI 32.9-38.6) in the study of 1995-1996, compared to the Toxoplasma study of 1987--1988 (45.8 %, 95 % CI 45.2-46.3). The steepest rise in seroprevalence still occurred among the subjects aged 25-44 years.

Declining seroprevalence of rubella antibodies among young Israeli adults: a 12-year comparison

Background. In March 2000, the Israel Defense Force (IDF) experienced an outbreak of rubella. No population-based rubella seroepidemiologic data were available for the 13-year period preceding the epidemic. Methods. We conducted a population-based seroprevalence study of rubella antibodies among 289 IDF recruits drafted in 1999. Results. We found that 69.2% of males and 90.8% of females in service were seropositive at recruitment in 1999, immediately before the outbreak. These rates were significantly lower than those last measured in 1987 (88% among males and 98.1% among females). Conclusions. Our findings indicate that this rubella outbreak among young adults was facilitated by a decrease in immunity to levels below those required for herd immunity, at which epidemic virus transmission was no longer blocked. This is most likely due to widespread pediatric vaccination coverage with incomplete catch-up immunization among adolescents and young adults. These findings serve as a reminder that changes to childhood vaccination programs may affect the epidemiology of disease among older segments of the population several years after the change is implemented.

A population-based seroprevalence study of hepatitis A virus using oral fluid in England and Wales.

Population-based seroprevalence studies provide important data on susceptible groups and the potential for future outbreaks. However, the invasive nature of serum collection has limited studies. This paper describes the first postal population-based survey using noninvasive oral fluid technology to collect antibody prevalence data in conjunction with extensive risk factor data to assess the distribution of immunity to common viral infections in England and Wales. These results pertain to hepatitis A virus (HAV). Approximately 5,500 oral fluid samples were collected between August 2001 and May 2002, as well as individual risk factor data through a questionnaire, from persons aged less than 45 years randomly sampled from general practices countrywide. Samples were tested for immunoglobulin G-specific antibody marking a past infection or immunity to HAV using an antibody-capture enzyme-linked immunosorbent assay. The age-specific HAV seroprevalences indicated a low incidence of infection (overall seroprevalence of 18.9% (95% confidence interval: 17.0, 20.9) and of 9.2% (95% confidence interval: 7.1, 11.3) after the exclusion of vaccinees). Vaccination proved the most important determinant of seropositivity. Ethnic minority groups were underrepresented, and adjustment increased the overall prevalence to 20.1% and to 12.1% in unvaccinated individuals. The availability of comprehensive risk factor data allowed the description of two risk profiles related to natural infection and vaccination.

Prevalence of tick-borne-encephalitis virus antibodies in Lithuania.

Clinical infections caused by tick-borne encephalitis virus (TBEV) are quite common in Lithuania and cause significant disease burden not only as acute cases but as chronic sequealeae as well. In order to evaluate the spread of the disease and risk factors, a population based seroprevalence study was done. about 1488 serum samples collected from healthy people from different parts of the country during the year 2000 were studied by hemagglutination inhibition (HI) method. For risk factor analysis detailed information was collected by a questionnaire. 44 samples (2.96%) were positive. This indicates that at least 1500 infections occur in the country annually. Seropositivity did not increase with increasing age. In certain areas, seropositivity was clearly higher than the average. Other living conditions or outdoor habits correlated poorly with seropositivity. Certain groups of people such as farmers, cattle breeders, or those having a summer cottage or spending time in the nature daily had increased risk. Seropositivity was significantly linked with meningoencephalitis without laboratory confirmation for TBE in the anamnesis, and drinking of goat milk. The study suggests that TBEV is prevalent in Lithuania. The data also supports the view that an increase in the incidence has occurred in the 1990s. The correlation between seropositivity and presumed risk factors do not seem strong enough to warrant a selective vaccination policy based on risk factors.

Non-participation in a population-based seroprevalence study of vaccine-preventable diseases.

To estimate the immunity of the Dutch population against vaccine-preventable diseases, a population-based serum bank was established. Since a multi-tiered approach to enroll eligible individuals was used, both the overall non-response selection and the effect, on this selection, of including additional participants and of excluding a subgroup of non-participants (i.e. those without questionnaire data) could be studied. For some characteristics associated with non-participation, an association with seroprevalence of vaccine-preventable diseases is likely (e.g. age, gender). For other characteristics (e.g. marital status, receipt of reminder, degree of urbanization) the association with immune status is unclear but probably small. If the distribution in the population, or information on all participants and non-participants, of the characteristic is available, then the effect on the seroprevalence can be estimated. However, investigators have to be aware that studying only a subgroup of non-participants might lead to a biased insight into non-participation selection. Furthermore, merely including additional participants might not always reduce this bias.

A population-based seroprevalence study in South Africa as a tool in the polio eradication initiative.

A seroprevalence study for poliomyelitis was carried out on a sample of sera from a serum bank used for a vitamin A study. Vaccination coverage was satisfactory (80% or more) in five of nine provinces, although a prevalence of antibody to polio of 80% or more was found in all provinces. Serologic immunity (i.e., the prevalence of neutralizing antibodies) exceeded vaccination coverage, suggesting secondary spread of vaccine virus. However, whether or not water was supplied through a piped system was not associated with secondary spread of vaccine virus to nonvaccinated children. Seroprevalence studies are a valuable adjunct to acute flaccid paralysis surveillance, which is the standard surveillance instrument for the poliomyelitis eradication initiative. The use of available and suitable serum banks for seroprevalence investigations is a relatively cheap monitoring option that can yield very valuable information for the eradication initiative.

HIV seroprevalence in emergency department patients: Portland, Oregon, 1988-1991.

In Portland, OR: 1) to determine the changes in HIV seroprevalence for ED patients from 1988 to 1991, 2) to define the characteristics of the HIV-positive ED patient, 3) to determine the hepatitis B seroprevalence of HIV-seropositive ED patients, and 4) to demonstrate the feasibility of an ED population-based surveillance investigation. A prospective, multiyear observational, cross-sectional, multicenter, population-based seroprevalence study was performed using seven urban hospital EDs. Serologic testing for HIV and hepatitis B was performed on excess blood obtained from ED patients. Four sampling periods were used at each hospital at 14-month intervals starting June 1988 and ending December 1991. The blood specimens were obtained concurrently at all the participating hospitals. Of 1,681 patients, 17 (1.0%) were HIV-positive. The HIV seroprevalence rate was relatively stable over time: 0.5% (2/444) in 1988, 1.7% (7/396) in 1989, 1% (3/296) in 1990, and 0.9% (5/545) in 1991. Most (94%) HIV patients were men, 100% were white, 81% were > or = 30 years old. Most (59%) of the HIV-positive patients also were positive for hepatitis B core antibody. Many (76%) of the HIV-positive patients were known to be positive by the emergency health care worker. HIV seroprevalence among the ED patients in Portland, OR, was generally stable from 1988 to 1991. Many HIV-positive patients also were hepatitis B-positive, thus representing a double occupational infectious disease risk to ED personnel. A significant minority (24%) of the HIV-positive patients were not known to be HIV-positive by the ED personnel. Universal precautions and hepatitis B immunization are paramount for reducing the risk of infectious disease due to exposure to body fluids.