Estimating the critical immunity threshold for preventing hepatitis A outbreaks in men who have sex with men.

Several outbreaks of hepatitis A in men who have sex with men (MSM) were reported in the 1980s and 1990s in Australia and other countries. An effective hepatitis A virus (HAV) vaccine has been available in Australia since 1994 and is recommended for high-risk groups including MSM. No outbreaks of hepatitis A in Australian MSM have been reported since 1996. In this study, we aimed to estimate HAV transmissibility in MSM populations in order to inform targets for vaccine coverage in such populations. We used mathematical models of HAV transmission in a MSM population to estimate the basic reproduction number (R 0) and the probability of an HAV epidemic occurring as a function of the immune proportion. We estimated a plausible range for R 0 of 1·71-3·67 for HAV in MSM and that sustained epidemics cannot occur once the proportion immune to HAV is greater than ~70%. To our knowledge this is the first estimate of R 0 and the critical population immunity threshold for HAV transmission in MSM. As HAV is no longer endemic in Australia or in most other developed countries, vaccination is the only means of maintaining population immunity >70%. Our findings provide impetus to promote HAV vaccination in high-risk groups such as MSM.

Participant centred safety surveillance of health care workers receiving influenza vaccination.

Following the introduction of mandatory influenza vaccination for staff working in high risk clinical areas in 2018, we conducted active surveillance for adverse events following immunisation utilising an automated online survey to vaccine recipients at three and 42 days post immunisation. Most participants 2285 (92%) agreed to participate; 515 (32%) staff reported any symptom and eight (1.6%) sought medical attention. The odds of having a reaction decreased with age by approximately 2% per year. The system was acceptable to staff, and the data demonstrated rates of reported symptoms within expected rates for influenza vaccines from clinical trials. Rates of medical attendance were similar to previous surveillance. Participant centred real-time safety surveillance proved useful in this staff influenza vaccination context, providing reassurance with expected rates and profile of common adverse events following staff influenza vaccination.

A method for determining the cut-off value of a varicella-zoster virus IgG enzyme immunoassay for immune status.

The cut-off optical density (OD) of an enzyme immunoassay (EIA) for IgG antibody to varicella-zoster virus (VZV) was established by application of a statistical technique to OD readings on sera from known susceptible and immune populations. Children aged one to three years who lacked complement fixation (CF) antibody were considered to be known susceptible subjects. Adults whose sera contained antibody by the CF test were considered to be known immune subjects. The method provides a valid alternative to previously used techniques of establishing a cut-off OD, above which reading the EIA can be taken to indicate immunity to varicella-zoster infection.

Determination and importance of varicella immune status of nursing staff in a children's hospital.

A survey of nurses at the Prince of Wales Children's Hospital was conducted to determine the prevalence of immunity to varicella-zoster virus (VZ) as defined by enzyme immunoassay (EIA), and to establish the value of history as a predictor of immunity. Of the 209 nurses surveyed, 51% could recall suffering VZ infection, and with a single exception, all of this group were immune. However, despite a 95% prevalence of immunity among all nurses, 46% of those found to be immune by EIA could not recollect having VZ infection. In the event of a hospital VZ outbreak, the latter group, without serological testing, would thus need to be regarded as susceptible, and this would create a major logistical problem in staffing the affected areas. We suggest, to minimize this cause of disruption to services, that all paediatric staff with patient contact should be asked at the time of recruitment if they recall suffering VZ infection. Those who give a positive response may be considered immune, but all other staff should have their immune status assessed by EIA at the earliest opportunity.

Designated "no smoking" areas provide from partial to no protection from environmental tobacco smoke.

OBJECTIVE: To determine the efficacy of designated "no smoking" areas in the hospitality industry as a means of providing protection from environmental tobacco smoke (ETS), and whether certain design features assist in achieving this end. METHODOLOGY: In the greater metropolitan region of Sydney, a representative group of 17 social and gaming clubs, licensed to serve alcoholic beverages and in which, apart from designated areas, smoking occurs, agreed to participate. In each establishment, simultaneous single measurements of atmospheric nicotine, particulate matter (10 microm; PM10) and carbon dioxide (CO2) levels were measured in a general use area and in a designated "no smoking" area during times of normal operation, together with the levels in outdoor air (PM10 and CO2 only). Analyses were made of these data to assess the extent to which persons using the "no smoking" areas were protected from exposure to ETS. RESULTS: By comparison with levels in general use areas, nicotine and particulate matter levels were significantly less in the "no smoking" areas, but were still readily detectable at higher than ambient levels. For nicotine, mean (SD) levels were 100.5 (45.3) microg/m3 in the areas where smoking occurred and 41.3 (16.1) microg/m3 in the "no smoking" areas. Corresponding PM10 levels were 460 (196) microg/m3 and 210 (210) microg/m3, while outdoor levels were 61 (23) microg/m3. The reduction in pollutants achieved through a separate room being designated "no smoking" was only marginally better than the reduction achieved when a "no smoking" area was contiguous with a smoking area. CO2 levels were relatively uninformative. CONCLUSION: Provision of designated "no smoking" areas in licensed (gaming) clubs in New South Wales, Australia, provides, at best, partial protection from ETS-typically about a 50% reduction in exposure. The protection afforded is less than users might reasonably have understood and is not comparable with protection afforded by prohibiting smoking on the premises.

Surveillance for tuberculosis among residents of hostels for homeless men.

Tuberculosis has been recognised as an important health problem among homeless persons. The New South Wales tuberculosis screening program for residents of hostels for the homeless has been in operation for several years, but has not yet been evaluated. This study reviewed the performance of the tuberculosis surveillance program (which uses mobile chest x-ray screening) between 1989 and 1993 at the five major hostels for homeless men in the eastern Sydney area. Reports of the screening x-rays and records of subsequent follow-up examinations at chest clinics were examined; information on cases detected by the screening program was compared with notifications in the same population. Of 3555 residents screened during 23 visits, 506 (14.2 per cent) were found to have an abnormal chest x-ray. However, only two active cases of tuberculosis were diagnosed as a result of the screening program, while seven cases were notified on the basis of clinical presentation. About 50 per cent of those with an abnormal chest x-ray from the screening program were lost to follow-up. Possible reasons for loss to follow-up were: long delays in making chest clinic appointments; short-stay residents changing shelters without trace; and high prevalence of severe mental illness or organic brain syndrome among residents. Raising awareness of the disease among primary health care and welfare staff who work with homeless men may be a more effective approach to improving identification of cases of active tuberculosis in this population.

Faecal pollution of ocean swimming pools and stormwater outlets in eastern Sydney.

We determined the levels of faecal contamination over a three-year period from 1991 to 1993 at selected ocean swimming pools and stormwater outlets to assess whether these levels represented a threat to public health. Three popular ocean swimming pools and three nearby stormwater outlets located in Sydney's eastern suburbs were included in the analysis. The ocean swimming pools consistently had elevated levels of faecal coliform bacteria; the highest microbe levels were observed in a pool used largely by children. Faecal coliform bacteria counts in the ocean pools at times reach levels likely to be associated with illness in bathers. Stormwater outlets at three locations had reducing counts over the three-year period. An improved system of sampling, testing and risk communication appears to be needed to reduce potential health risks to users of these popular ocean pools.

Fragmentation of scheduled visits and missed doses among infants receiving multiple injected vaccines.

A retrospective cohort study was used to determine the extent to which immunisation visits due in the first year of life are split into separate visits. A one-month birth cohort of infants registered in early childhood health centres in the former Eastern Sydney Health Area was followed up when the infants were 8 to 11 months of age. A telephone questionnaire sought documented dates of each dose in the primary series of diphtheria-tetanus-pertussis (DTP), Haemophilus influenzae type b (Hib) and hepatitis B (HBV) vaccination. Of the 141 subjects, 130 had received all due doses of DTP and Hib vaccines and 63 (45 per cent) had been enrolled in the neonatal hepatitis B program. Infants in the latter group received the first DTP-Hib dose on average one week later than did those not in the hepatitis B program (DTP, P = 0.016; Hib, P = 0.047). The greatest percentage of missed DTP or Hib doses occurred in infants not receiving HBV vaccination (7.1 per cent of doses) or those high-risk infants enrolled in the neonatal hepatitis B program (2.9 per cent). Overall, 12 infants had 28 (6.9 per cent) of the 404 possible scheduled visits fragmented into two separate visits. In all cases, parents reported that this was at the suggestion of the general practitioner. We found no greater likelihood of fragmentation for infants who had also received hepatitis B vaccine. Only 17 infants (29 per cent) had received the third hepatitis B vaccine and DTP doses at the same visit, as recommended. These findings confirm anecdotal reports of fragmentation of scheduled visits and missed doses for infants due to receive multiple injections, and some delay in uptake among those receiving hepatitis B vaccine. Universal infant hepatitis B immunisation should not be considered until combination vaccines (which should also include a Hib component) become available in Australia.

Varicella-zoster virus infection in Australia.

OBJECTIVE: To determine the epidemiology of varicella-zoster virus (VZV) infection in Australia using currently available data sources. DESIGN: Analysis of national death data (23 years), congenital and neonatal cases (one year) and attendances at sentinel general practices (two years); hospital admissions in NSW and SA (six years); serological studies in 1995 involving antenatal clinics in Sydney and Brisbane and child-care centre staff and refugees in Sydney; and case-ascertainment in 1995 in South Western Sydney among public hospital staff, child-care centre staff and the community. RESULTS: In Australia, there have been an average of 3.5 deaths from chickenpox (mostly children) and 11 from herpes zoster (mostly older people) each year since 1980. The crude death rate for chickenpox has declined (p > 0.05). In 1995, there were 14 cases of neonatal and two of congenital varicella. Average annual admission rates for NSW and SA showed 1,200 hospital bed-days used for chickenpox, more than 20% with complications, and more than 7,300 bed days for zoster; annually more than 880 in-patient admissions were complicated by VZV. Most people encounter the virus in their first 15 years, but some remain susceptible into their 20s; 25% of cases and 37% of hospital admissions for chickenpox occur in people > or = 15 years of age. CONCLUSION: VZV infection involves people of all ages. It causes substantial morbidity and mortality, particularly at the extremes of life. The death rate from chickenpox but not zoster has fallen since the introduction of acyclovir in the 1980s. Surveillance of VZV infection must be given priority once vaccines become available, to monitor changes in morbidity and mortality.

Transmission of hepatitis C virus to recipients of parenteral vitamin therapy in a primary care facility.

BACKGROUND AND OBJECTIVES: The Australian prevalence of hepatitis C virus (HCV) is approximately 1%, with the majority of cases acquired through injecting drug use. However, occasionally HCV infection occurs in healthcare settings. Three new HCV infections were identified amongst patients attending a general practice in Sydney, Australia, specialising in parenteral vitamin therapy. STUDY DESIGN: An investigation was conducted to identify the source of infection and mechanism of transmission. Molecular analysis was conducted by sequencing the HCV NS5A, Core and NS5B regions. RESULTS: Two sources were identified using molecular epidemiology - a genotype 3a case was the source for a case acquired in late 2004 and a genotype 1b case the source for one case acquired in late 2006 and another in early 2007. The common risk factor was parenteral vitamin C therapy. CONCLUSIONS: Inadequate infection control was apparent and likely to have resulted in blood contamination of the healthcare workers, their equipment, the clinic environment and parenteral medications. Molecular and clinical epidemiology clearly identified parenteral transmission of HCV, highlighting the risks of blood contamination of parenteral equipment and use of multi-dose flasks on more than one patient.

Immunisation state and its documentation in hospital patients.

Two prospective surveys of the immunisation state and its documentation were conducted among children under 2 years old attending a children's hospital. A survey of 111 children attending the casualty or outpatient departments showed that, according to reliable records, 106 (95%) were fully immunised for age with oral polio vaccine, 93 (84%) with triple antigen, and 26 of 33 children greater than or equal to 16 months of age (79%) with measles-mumps vaccine. A survey of 204 inpatients showed that, according to verified records, significantly fewer inpatients than outpatients were fully immunised for age with oral polio vaccine (176, 86%) and with triple antigen (144, 71%). The proportion of inpatients vaccinated with measles-mumps vaccine was 81% (48 of 59). The inpatient figures are all lower than the 95% goal of current child immunisation programmes. Although parents of 98% of inpatients had a personal health record for the child, it was available at the time of admission for less than half the children. Lack of use of the personal health record by admitting medical staff was reflected in incorrect or absent documentation of the immunisation state in 17 of 49 (35%) of the records of children verified to have inadequate immunisations. Parents and health care staff need to be educated in the optimal use of the personal health record. Hospital paediatric staff need to be encouraged to verify the immunisation state of all young children, on admission, and arrange to rectify any deficiency found.

Infections in day care.

The number of preschool-aged children who attend day care has increased dramatically in recent years. Factors promoting spread of infections in this setting include crowding, lack of hygiene, high prevalence of early exploratory behaviors, and the likelihood of many susceptible children being in close contact. As a result, children attending day care experience a great number of episodes of respiratory and gastrointestinal illness than do other children. Moreover, the risk of a number of specific infections, including Haemophilus influenzae type b and hepatitis A, is increased by attendance in day care. Day-care staff are at increased risk of a number of infections, some of which, including cytomegalovirus and parvovirus B19, may have adverse consequences to a fetus. The presence of children in day care increases the risk of illness among staff and family members and may promote the circulation of infections in the community as a whole.

Control of infections in child care.

The control of infections in child-care centres involves vaccination of children and staff, attention to hygiene (particularly to handwashing), exclusion of children (and employees) while infectious and/or grouping of infectious children, separation of toilet-trained children from those in nappies, and judicious use of antimicrobial agents and vaccination during outbreaks. By reporting cases of infectious diseases in patients with child-care contact to public health authorities, doctors can assist in controlling such diseases in child care.

Varicella vaccine in post-exposure prophylaxis.

Evidence concerning the effectiveness of Oka-based varicella vaccines when administered following exposure to varicella zoster virus in domestic and hospital settings is reviewed. The evidence appears to support post-exposure use of Oka-derived varicella vaccines in children within 3 days of rash onset in the index case. Despite vaccination, a small proportion will develop mild, but infectious, chickenpox, especially if they have been exposed in the household setting. Controlled studies of post-exposure prophylaxis in adults using both Varilrix and Varivax II are still needed. The applicability of this approach to disease control in health care facilities and in community settings warrants wider discussion.

Another vaccine, another treadmill?

OBJECTIVE: Attention is drawn to possible disadvantages arising from the introduction of universal varicella vaccination in infancy. METHODOLOGY: Comparisons are made between universal infant varicella vaccination and the current measles immunization programme, and a review of current literature on age-specific complications of varicella and cost-benefit analyses of varicella vaccination. RESULTS: Universal infant vaccination will cause a greater proportion of varicella cases to occur in adults, including pregnant women, who are at greater risk of serious complications compared to children. Although economic costs resulting from lost time from work will fall dramatically, health costs may rise. CONCLUSIONS: Universal infant vaccination should only be considered if measles is first controlled, and then only if more information on duration of protection becomes available and combined measles-mumps-rubella-varicella vaccines are approved.

Infection control in child care settings.

Over one-third of all under five year old Australian children use some form of licensed child care. The majority of research on infectious diseases in children using care, mainly emanating from North American and Scandinavia, suggests that children in preschool or long day care suffer more frequent infections and more days of illness than those cared for at home or in family day care. In order to minimise these risks it is necessary to apply infection control principles. In this article infection risk factors are outlined and recommendations for immunisation, preventative practices, the use of antibiotics and outbreak management are presented.