Journal club summaries - 2013

 

Measuring vaccine confidence: analysis of data obtained by a media surveillance system used to analyse public concerns about vaccines

Larson HJ, Smith DM, Paterson P, et al.
The Lancet Infectious Diseases 2013;13(7):606-13 
Link to abstract

While immunisation has been successful in reducing the global burden of illness and death, a range of issues still affect public confidence in vaccines. The intensity, speed and effects of public opinion about vaccination are growing with new modes of communication. This study aimed to develop a new application of existing surveillance systems to detect and characterise early signs of vaccine issues and design an approach to assess the priority of each concern. The researchers postulated that media monitoring might provide important information regarding perceived problems with vaccines or immunisation programs that would take longer to register through official channels. This information could then be used to tailor more effective and timely strategies to address these concerns before an effect on vaccination uptake or disease outbreak is observed. 

Following preliminary research by The Vaccine Confidence Project, media reports were obtained using the HealthMap automated data collection system which was adapted to monitor online reports about vaccines, vaccination programs, and vaccine-preventable diseases. Reports were manually analysed for content and categorised by concerns, vaccine, disease, location and source as well as overall positive or negative sentiment towards vaccines. Using pre-defined criteria they were then given a priority level depending on the timing and seriousness of the reported event. 

10,380 reports from 144 countries were obtained between 1 May 2011 and 30 April 2012. 7,171 (69%) contained positive or neutral content and 3,209 (31%) contained negative content. Of the negative reports, 1,977 (24%) were associated with impacts on vaccine programs and disease outbreaks; 1,726 (21%) with beliefs, awareness and perceptions; 1,371 (16%) with vaccine safety; and 1,336 (16%) with vaccine delivery programs. Proportions of positive and negative reports for each category changed when the data was disaggregated by country and vaccine type indicating potentially strong differences in vaccine confidence, priorities or opinions. Evidence of global dissemination of vaccine concerns was also apparent. 

It is clear that the nature of public concerns about vaccines is complex and highly diverse. This research established a robust system for the real-time collection, categorisation and prioritisation of vaccine sentiments that could be utilised to detect local confidence issues and address public questions and concerns. However, this field of work is currently highly resource intensive and requires further investigation regarding its potential benefits to the implementation of immunisation programs.

Presented by Ms Amy Vassallo, Research Officer, NCIRS

Mortality rates and cause-of-death patterns in a vaccinated population

McCarthy NL, Weintraub E, Vellozzi C, et. al. 
American Journal of Preventive Medicine 2013;45(1):91-7
Link to abstract

The Vaccine Safety Datalink (VSD) is a collaborative project between the United States Centers for Disease Control and ten Managed Care Organizations (MCOs) designed to monitor immunisation safety and conduct population-based immunisation safety studies.

This study provides the methodology and analyses conducted using the VSD to calculate background mortality rates and describe causes of death following immunisation. The results demonstrate a healthy vaccinee effect, with mortality rates lowest in the days immediately following vaccination. Background mortality rates in a vaccinated population are useful in evaluating new vaccines and providing baseline data to detect unusual signals due to vaccine introduction.

Presented by Dr Shopna Bag, Public Health Registrar, NCIRS

Event-based surveillance in the Western Pacific Region – Field Epidemiology Training Program Fellowship 2013

May Chiew, Master of Applied Epidemiology Scholar, gave a summary of event-based surveillance (EBS). This was based on her experience from the fellowship program that she undertook during August 2013 at the World Health Organization Western Pacific Regional Office (WPRO). The fellowship consisted of conducting EBS – the organised and rapid capture of information about events that are a potential risk to public health. Examples of EBS include the media, healthcare workers, community leaders and non-governmental organisations. Conducting EBS allows for more timely detection of public health events with minimal resources required and is part of the revised International Health Regulations (IHR) 2005. Additionally, EBS is a key component to one of the eight focus areas of the Asia Pacific Strategy for Emerging Disease (APSED). Using the media for EBS can have some limitations; media reports are based on newsworthiness and, in some countries, the media can be state controlled and specificity of reports is also low. Despite this, media reports accounted for approximately 70% of all reported public health events between 2008 and 2010 in the Western Pacific Region. This indicates the importance of the media as an information source for potential public health events, particularly when it translates to timely detection and response. 

Presented by Ms May Chiew, Master of Applied Epidemiology Scholar, NCIRS

Importance of timing of maternal combined tetanus, diphtheria, and acellular pertussis (Tdap) immunization and protection of young infants

Healy CM, Rench MA, Baker CJ 
Clinical Infectious Diseases 2013;56(4):539-44
Link to abstract

There are high levels of pertussis morbidity and mortality in infants too young to be vaccinated. An initial strategy to address this was ‘cocooning’, vaccinating close adult contacts of infants with dTpa. Both overseas and in Australia there have been barriers to the success of this strategy, such as implementation in hospitals and timely delivery of the vaccine to mothers of newborns. A subsequent strategy has been maternal immunisation with dTpa during pregnancy. This has been recommended in the United States since 2011, has been used recently in England and New Zealand as an outbreak response, and is included as an alternative option to cocooning in the 10th edition of The Australian Immunisation Handbook. A question that now arises is how often should women receive a dose of dTpa? This study aimed to determine pertussis-specific IgG levels in plasma at delivery from mothers who received dTpa vaccine within the prior 2 years and to assess the levels in cord serum from infants born to these women. The study also aimed to estimate whether passively acquired maternal IgG levels could potentially protect infants through the first few months of life, until they were old enough for their first dose of DTPa. The study found that maternal antibodies waned quickly, even in women immunised during pregnancy, and that pertussis antigen IgG levels in infants were unlikely to be high enough to passively protect them until 2 to 3 months of age. Based on this data, in October 2012 a recommendation was made in the United States for women to receive a dose of dTpa during every pregnancy. In Australia we continue to have the recommendation that is in the 10th edition of The Australian Immunisation Handbook, which states that pregnant/post-partum women should receive another dose of dTpa if it is 5 years or more since their last dose.

Presented by Dr Helen Quinn, Research Fellow, NCIRS

Vaccination site and risk of local reactions in children 1 through 6 years of age

Jackson LA, Peterson D, Nelson JC, et al.
Pediatrics 2013;131(2):283-9
Link to abstract

Conducted in the USA using the Vaccine Safety Datalink collaboration, this study aimed to assess whether the occurrence of medically attended local reactions to intramuscularly administered vaccines varied by injection site (arm vs thigh) in children aged between 1 and 6 years. The study included 1.4 million children who had received 6 million intramuscular (IM) vaccines during 2002–2009. The data were analysed to look at reactions to vaccines most commonly given alone (i.e. inactivated influenza vaccine, hepatitis A and DTaP) as well as to evaluate reactions in children who received exactly two vaccines on the same day. Results showed that injection site reactions to hepatitis A vaccine and inactivated influenza vaccine are relatively uncommon. However, when a reaction did occur, there was no difference in risk of these whether the vaccine site was an arm or a leg. Injection site reactions were found to be more common when DTaP was used and there were higher rates of reaction in the arm versus the leg. In children who received two IM vaccines on the same day there was also a higher rate of medically attended local reaction for children who had received the vaccines in the arm versus the thigh as well as when DTaP was one of the vaccine combinations. When the vaccine combination did not include DTaP there was no evidence of increased local reaction with arm administration. It should be noted that the US schedule for DTaP vaccination includes the first booster dose at 18 months of age and the second booster at 4 years. Australia removed the 18 month dose of DTPa in 2003. The USA currently recommends the thigh as the appropriate site for the administration of vaccines to children under 3 years of age. The Australian Immunisation Handbook 10th edition recommends that from the age of 12 months the deltoid is appropriate for administration of vaccines but the thigh can be used as an alternate site.

Pharmacokinetic modeling as an approach to assessing the safety of residual formaldehyde in infant vaccines

Mitkus RJ, Hess MA, Schwartz SL
Vaccine 2013;31(25):2738-43
Link to abstract

As part of the ongoing evaluation of the safety of biological products the FDA (US Food and Drug Administration) performed an assessment of formaldehyde in infant vaccines using a physiologically based pharmacokinetic (PBPK) model. This allowed for an estimation of formaldehyde concentrations in blood and total body water following exposure to formaldehyde-containing vaccines given at a single medical visit and compared to endogenous background levels in a model 2-month-old-infant. The results from the model revealed that following a single dose of 200 micrograms (the maximum amount found in a vaccine used in the USA), formaldehyde is completely removed from the injection site within 30 minutes. This amount and rate of metabolism is considered to equal less than 1% of the endogenous level of formaldehyde. Therefore, the authors concluded that the small amount of residual formaldehyde found in vaccines after the manufacturing process continues to be at safe levels.

Presented by Ms Kath Cannings, Immunisation CNC, NCIRS

Genital warts in young Australians five years into national human papillomavirus vaccination programme: national surveillance data

Ali H, Donovan B, Wand H, et al.
BMJ 2013;346:f2032
Link to abstract

The quadrivalent human papillomavirus (HPV) vaccine Gardasil (covering types 6, 11, 16, and 18) is funded for use in the Australian HPV School Vaccination Program. The vaccine program commenced in 2007 for girls 12 to 13 years of age and since February 2013 has also been offered to boys. From 2007 to 2009, catch-up programs offered free vaccination for women up to 26 years of age. Clinical trials have demonstrated up to 98% vaccine efficacy against early forms of cervical malignancy and 100% efficacy against warts in HPV naïve subjects. 

This study aimed to assess the effect of the vaccination program, 5 years after its introduction, on genital wart presentations to eight sexual health clinics across Australia, by looking at proportions of new patients found to have genital warts. The authors had previously reported a 59% reduction in warts in women and 39% in heterosexual men 12 to 26 years of age, after 2 years of the vaccination program. Retrospective data was provided by these eight centres on all Australian-born patients presenting for the first time between 2004 and 2011. Data was collected as to whether genital warts were present. Two centres collected self-reported HPV vaccination status. The pre-vaccination period was defined as January 2004 to June 2007 and the post vaccination period as July 2007 to December 2011. 

The results showed significant reductions, from 2007 to 2011, of 93% in genital wart presentations in women <21 years of age, and 73% in women 21 to 30 years of age. There was no change in women >30 years of age who would have been ineligible for any free vaccination. Herd immunity was significant with 82% reduction in genital warts in heterosexual men <21 years of age and 51% reduction in men 21 to 30 years of age, but no significant change in men >30 years of age. A significant decline found in homosexual but not bisexual men who have sex with men was thought to be artefactual due to increased asymptomatic presentations through successful triaging of men who have sex with men into sexual health services. In the most recent year, there were no genital wart presentations among 235 vaccinated women <21 years of age. A comparative increase in the proportion of subjects with chlamydia diagnosed suggested findings were not due to decreased risk-taking behaviour.

This study reports a larger decline in genital warts after HPV vaccination introduction than previous studies, most likely due to higher relative HPV vaccination coverage within Australia, and confirms its high efficacy against genital warts in a population-based setting.

Presented by Dr Jean Li-Kim-Moy, Clinical Research Fellow, NCIRS

Persistence of the efficacy of zoster vaccine in the shingles prevention study and the short-term persistence substudy

Schmader KE, Oxman MN, Levin MJ, et al. 
Clinical Infectious Diseases 2012;55(10):1320-8
Link to abstract

This study presents the results of the Short-Term Persistence Substudy (STPS), an extension of the Shingles Prevention Study (SPS), investigating the vaccine efficacy of Zostavax 4 to 7 years post vaccination. The STPS re-enrolled 7,320 SPS participants from the vaccine group and 6,950 SPS participants from the placebo group. The participants were followed up each year through year 7 after vaccination for three endpoints: vaccine efficacies (VE) in the reduction of (1) herpes zoster (HZ) burden of illness - measured by the Zoster Brief Pain Inventory (ZBPI); (2) HZ incidence - cases confirmed by clinical diagnosis, PCR assay and/or virus culture; (3) post-herpetic neuralgia (PHN) - measured by a 10-point rating scale for the severity of pain. The comparison of SPS and STPS showed that the VE for HZ burden of illness decreased from 61% to 50%; VE for HZ incidence decreased from 51% to 40%; VE for PHN incidence decreased from 67% to 60%. The duration of protection 5 years after vaccination is uncertain, but waning in immunity and decrease in vaccine efficacy are evident after year 1. Further studies conducted by the SPS team such as the Long-Term Persistence Substudy (LTPS) and Long-Term Effectiveness of Zostavax will provide more information regarding duration of protection and inform the need for a booster dose for older adults. 

Presented by Dr Maria Chow, Research Officer, NCIRS

The economic evaluation of vaccination programs: empirical research on underlying ethical issues

Guest speaker: Mr Jeroen Luyten
International PhD student, Centre for Health Economics Research & Modelling Infectious Diseases (CHERMID), University of Antwerp

Roughly speaking, there are two ethical issues related to cost-effectiveness analysis of vaccination. Firstly, does the allocation of resources using costs per Quality Adjusted Life Year (QALY) correctly value the merits of vaccination? Secondly, cost-effectiveness is influenced by the presence or absence of herd immunity effects, which is in turn determined by the level of vaccine uptake in the population. In case the latter is low, this raises the issue whether people have a moral duty to become vaccinated and which policy options are acceptable to increase coverage. 

Two studies conducted in Belgium were presented which examine questions arising from these ethical issues.

The first study sought to explore which characteristics of healthcare programs are morally relevant to the general public, whether prevention or cure is more important, and if there is a difference in the opinions of different population subgroups. Forced choice analysis was used to quantify which health programs members of the public felt should be publicly funded. A sample of 750 people between 18 and 75 years, which was representative of the population for gender, age, province and education, was used to generate 10,500 choices. All variables explored had a significant effect but lifestyle and age of the patient were found to be of special importance. Further to this, interaction was identified between age and type (cure or prevention), and between severity of illness and type. Differences were observed in the responses of various population subgroups, among others for age, education, gender, health state and health-related lifestyle. In summary, patient age and lifestyle were important considerations in the way people set priorities. Prevention was more valuable at a younger age and for serious disease, and there were large differences in the results for population subgroups.

The second study examined attitudes to vaccination and to various policy options that implied trade-offs between efficiency, equity and individual autonomy. A sample of 1,050 people was recruited through random digit dialling (42% response rate) to participate in the survey. The survey included background questions and (among others) their “social orientation” (see Triandis & Gelfland). They were also given 15 different infectious disease scenarios with three vaccination policy options: vaccination of target groups only (e.g. travellers or immigrants, a comparatively efficient approach); voluntary universal vaccination (comparatively inefficient); and no vaccination. The results showed that people tended to differentiate between programs for different target groups (e.g. people were more supportive of targeted approaches for travellers and were not supportive of such approaches for migrants). It was found that incentives for uptake had a moderate influence, and that social orientation seemed to be related to people’s preference for voluntary, compulsory, accountability or reward- oriented approaches. In summary, public support is an important facet of vaccination programs, and people’s social orientation is a predictor of their attitudes to different policy options, and their acceptance of incentives.

The research approach used here can be used to explore the Australian public’s response to similar ethical questions.

Summary prepared by Ms Kerrie Wiley, PhD Candidate, Social Research, NCIRS

Immunogenicity of 2 doses of HPV vaccine in younger adolescents vs 3 doses in young women: a randomized clinical trial

Dobson SR, McNeil S, Dionne M, et al. 
JAMA 2013;309(17):1793-802
Link to abstract

Evidence on 2 versus 3 dose HPV vaccine schedules is of interest for vaccine policy makers considering implementation of HPV vaccination programs. It would be expected that a 2-dose HPV vaccine schedule would offer advantages such as reduced cost of vaccination, easier implementation and higher course completion. This paper describes the results of a randomised phase III, non-inferiority, immunogenicity study of a 2-dose schedule of the 4vHPV vaccine in adolescent girls. Girls aged 9 to 13 years were randomised to receive either the standard 3-dose schedule (months 0, 2 and 6) or 2 doses (months 0 and 6). The third arm was young women aged 16 to 26 years who received the standard 3-dose schedule. The antibody response (geometric mean titres; GMT) was measured at 0, 7, 18, 24 and 36 months. The main study outcome was to determine if the immunogenicity of the 2-dose schedule in adolescent girls is non-inferior to the 3-dose schedule in young women for whom vaccine efficacy data is available. The definition of non-inferiority was the lower bound of the 95% confidence interval for a GMT ratio greater than 0.5. Overall, the 4vHPV was immunogenic across the study arms with over 99% of participants seropositive at month 7. In adolescent girls, the 2-dose schedule resulted in non-inferior GMTs for all vaccine HPV types to what was achieved in young women at both month 7 and month 36. Similarly, adolescent girls who received 2 doses of 4vHPV had a non-inferior antibody response for all 4 HPV types at month 7, compared to girls who received 3 doses. However, when comparing 2 doses versus 3 doses in adolescent girls, non-inferiority was lost for HPV18 by month 24 and for HPV6 by month 36. 

Two limitations in the study which influence the interpretation of these results is the lack of sensitivity of the assay used (cLIA) for detection of antibodies in response to vaccination. This is primarily because the employed method only detects a single neutralising antibody, thus the presented GMTs may not be a true reflection of the overall antibody response. Related to this is the lack of clinical meaningfulness to the non-inferiority criteria used in the studies, hampered because there is no correlate of protection for HPV infection and/or disease. 

Presented by Dr Melina Georgousakis, Senior Research Officer, NCIRS

The impact of social networks on parents’ vaccination decisions

Brunson EK
Pediatrics 2013;131(5): e1397-404
Link to abstract

When deciding whether to vaccinate their children, parents rarely reach their decision in isolation. Research has shown that they are influenced by their social networks, which include people such as healthcare professionals, family and friends, and information sources such as websites, books and the mass media.

This study used egocentric network analysis to:

  1. Examine parents’ networks specifically relating to vaccination decisions as to whether they conformed fully to the national schedule or did not.
  2. Test the a priori hypothesis that parents’ people and source networks are better predictors of vaccination decisions than more conventional variables such as demographics and perceptions.

US-born first-time parents with a child up to 18 months old were recruited from King County in Washington state, USA, an area known to have lower than average vaccination rates. Non-random recruitment methods used flyers posted at local community centres, baby stores, coffee shops and healthcare providers. 

Participants completed an online survey with three modules examining social networks (people and information sources), vaccine perceptions and decision-making, and demographics. Parents were divided into two groups: those who followed the nationally recommended schedule in full and on time (‘Conformers’) and those who did not, either through delayed or selective vaccination, or no vaccination at all (‘Non-conformers’). Three logistic regression models were run for the Respondent (demographics), People network, and Source (information) network. The models were compared using Akaike Information Criterion (AIC) values, with the model having the lowest AIC value being that with the comparatively best fit.

The survey was completed by 196 eligible parents (126 conformers and 70 non-conformers). The two groups were similar demographically, the only significant differences being parents’ average perception of vaccination (measured using a Likert scale) and their intention to have their child fully vaccinated by the time they began school.

On average, non-conformers had a larger people network containing a higher number of females, and a higher number of people recommending non-conformity. A higher percentage of non-conformers had a source network, and they contained a higher number of sources than conformers.

The AIC for the Respondent, People and Source networks were calculated as 163.1, 99.9 and 168.3, respectively, implying that social networks, particularly people networks, play a significant role in parents’ vaccination decision-making. Of the variables considered, the percentage of people in parents’ networks recommending non-conformity to the vaccination schedule was the most predictive of conformity by the parent.

The study author recommends that interventions promoting childhood vaccination should be broad-reaching rather than specifically targeting parents alone, so that other people whom parents are likely to consult are also included.

Presented by Ms Kerrie Wiley, PhD student – Social Research, NCIRS

Infectious disease burden and vaccination needs among asylees versus refugees, District of Columbia

Chai SJ, Davies-Cole J, Cookson ST 
Clinical Infectious Diseases 2013;56(5):652-8
Link to abstract

Since 1990, the USA has resettled over 2 million persecuted persons from around the world. The USA classifies these persons into two groups based on where they are located when they apply for asylum. Refugees are persons who apply for and are granted asylum status while outside the USA, and asylees are persons who apply for and are granted asylum while already present inside the USA. 

Refugees are medically screened overseas before departure (laboratory screening for infectious tuberculosis and syphilis) and again shortly after arrival in the USA. Upon arrival, the Centers for Disease Control and Prevention (CDC) and the assigned state health department and humanitarian volunteer agency are notified. Volunteer agencies arrange for post arrival medical screening and social services. 

In contrast, asylees undergo minimal or no consistent medical screening before, during or after they are granted asylum. Asylees enter the USA in multiple ways, including as tourists, students or undocumented immigrants and usually enter as single individuals. When a person applies for or is granted asylum, the CDC and US states are not notified of their existence and humanitarian volunteer agencies are not regularly funded to support them.

This study was a retrospective cohort study of 630 asylees and 151 refugees referred to the District of Columbia (DC) Department of Health screening program for an initial US medical screening during September 2003 to August 2007. The objectives of the study were: (1) to compare health status indicators and time to receipt of a medical screening of newly screened DC asylees with DC refugees, and (2) to compare health status indicators of DC asylees with the general US population into which they have resettled

Health status indicators were chosen based on overseas refugee screening protocols and prior refugee studies. They assessed the prevalence of latent tuberculosis infection, HIV and hepatitis B seropositivity, intestinal parasite test positivity, need for vaccinations, and time from date of US arrival to receipt of screening.

Immunisation histories were reviewed during medical screening using age-specific US Advisory Committee on Immunization Practices (ACIP) recommendations. Vaccinations were considered necessary if they were inadequate or not previously documented. Data were available for analysis of hepatitis B, polio, measles-mumps-rubella (MMR), and diphtheria-tetanus-acellular pertussis (DTaP and Tdap) or tetanus-diphtheria (Td) booster vaccinations among children, and MMR and Tdap or Td vaccinations among adults.

Asylees in DC had a similar prevalence as refugees of latent tuberculosis infection, pathogenic intestinal parasites, and need for adult vaccinations. Asylees were screened significantly later after US arrival than refugees. Asylees had higher prevalence of latent tuberculosis infection, hepatitis B and HIV seropositivity, and child and adult vaccination needs than the US population.

This study suggests that asylees in DC have similar infectious disease burden and prevention needs as refugees and should be screened with the same urgency. Because applicants for US asylum are not linked to prompt medical screenings, DC asylees are typically screened much later, placing them and the US communities they live in at risk.

The Australian perspective
The Australian Medical Association has a Position Statement On The Health Care of Asylum Seekers and Refugees. Below is an extract from this statement. 
“To determine their specific health needs, all asylum seekers and refugees should undergo comprehensive and timely health assessments in a culturally appropriate manner by suitably trained medical practitioners as part of a primary health care team. This assessment will be used to establish ongoing care.
All asylum seekers and refugees should have access to the same level of health care as all Australian citizens. In addition, it should be ensured that their special needs, including cultural, linguistic, and health-related, are addressed.
A national statutory body of clinical experts independent of governments should be established with the power to investigate and advise regarding the health and welfare of asylum seekers and refugees.”

Presented by Mr Brynley Hull, Epidemiologist, NCIRS

Long-term effectiveness of varicella vaccine: a 14-year, prospective cohort study

Baxter R, Ray P, Tran TN, et al. 
Pediatrics 2013;131(5):e1389-96
Link to abstract

Varicella, prior to immunisation, was an almost universal infection (over 90% of individuals infected by 20 years of age) which rarely is associated with serious complications, more commonly in the immunocompromised or in adults. A vaccine was first licensed in the USA in 1995 and shortly thereafter recommended by the Advisory Committee on Immunization Practices (ACIP) routinely. Previous post-licensure studies have documented 1-dose effectiveness at 80–94%. Breakthrough infections, however, do occur and were the basis for ACIP recommendations of a second dose in children 4–6 years of age in 2006, with available studies suggesting effectiveness of 98%. The effect of the vaccine on rates of herpes zoster (HZ) are less well known. There have been concerns that routine immunisation in children may affect natural immune-boosting in individuals and lead to an increase in HZ rates.

This study aimed to assess the long-term effectiveness of varicella vaccine and its impact on the epidemiology of varicella and HZ. It was a prospective 14-year study (1995–2009) of a vaccinated cohort of 7,585 US children aged 12–23 months, vaccinated between June and November 2005, and followed to assess rates of breakthrough varicella or HZ. Six-monthly phone calls were used to document infections during this period. Annual rates per 1,000 person-years were calculated for varicella and relative risk for herpes zoster of vaccinated individuals and these were compared to historical rates calculated from age-based population studies in the pre-vaccine era. A group of 2,826 children within the study also received a second dose between 2006 and 2009 and had a shorter period of follow-up. Almost complete follow-up was achieved for 97.4% (7,386) of the original cohort.

The authors were able to demonstrate the average incidence of breakthrough varicella was 15.9 per 1,000 person years (PY), roughly a 9–10 fold decrease from historical rates of varicella in the pre-vaccine era. A steady decrease in incidence over the course of the study was demonstrated with the effect of increasing herd immunity and decreased disease prevalence, with a breakthrough rate of 2.0 per 1,000 PY in the last year of the study. No breakthrough cases occurred after the second dose. End of study vaccine effectiveness was 90%. HZ relative risk was 0.61 by study end, suggesting an approximately 40% reduction in HZ rates in vaccinated children up to 14 years of age. The authors concluded the vaccine was effective against chickenpox and provided excellent protection against moderate to severe disease, with no evidence of waning immunity over time. Additionally there were possible reductions in the risk of HZ in vaccinated children.

Presented by Dr Jean Li-Kim-Moy, Clinical Research Fellow, NCIRS

Implementation of a hepatitis A/B vaccination program using an accelerated schedule among high-risk inmates, Los Angeles County Jail, 2007–2010

Costumbrado J, Stirland A, Cox G, et al.
Vaccine 2012;30(48):6878-82
Link to abstract

Inmates of prisons are at increased risk of complications from hepatitis infections and have a high prevalence of other risk factors for liver disease such as poly-pharmacy, use of illegal drugs, unsafe tattooing practices, alcoholism, and human immunodeficiency virus (HIV) infection. The aim of this study was to describe the hepatitis A/B immunisation program using an accelerated schedule in a US gaol. In April 2007, the FDA approved the accelerated schedule for the combined hepatitis A/B vaccine. The accelerated vaccine schedule was given at day 0 (day of vaccination), 7 days, 21–30 days and as a 12-month booster. In August 2007, a 1-year hepatitis vaccination project began in the LA County Jail, Men’s Central Jail. Data from the vaccine program and the lessons learned from their experience is presented in this study. A vaccine record card documenting patient information was generated for each inmate who received vaccine. A next-dose card was given to each inmate after vaccination, which included a record of hepatitis vaccines administered, due date for the next dose, information on sexual health clinics, website and helpline. Data in this analysis were collected from the beginning of the program in August 2007 to June 2010. Vaccinated and unvaccinated inmates screened for sexually transmitted infections (STIs) were compared. There were no differences by age or race/ethnic group between vaccinated and unvaccinated inmates. Nearly 4,000 doses were administered over a 42-month period and individuals with STI history were more likely to receive at least one dose of vaccine compared to those without STI history. Offering vaccine to gaol personnel in sight of the inmates helped dispel distrust or fear of vaccination among inmates. However, vaccine acceptance rates were not measured to determine the factors that increased enrolment and retention in the program. Other limitations of the study were unavailability of serological data and cost-effective analyses.

Presented by Dr Aditi Dey, Manager, Surveillance, NCIRS

Factors underlying parental decisions about combination childhood vaccinations including MMR: a systematic review

Brown KF, Kroll JS, Hudson MJ, et al.
Vaccine 2010;28(26):4235-48
Link to abstract

This systematic review of 31 publications reports on data spanning 20 years that investigated parental factors that have been found to influence vaccination decisions. The review itself was of a good quality, with the minor exception of some specific search terms used to locate the included articles. Included studies were variable in their quality, with mode of paper quality assessed at half of the possible quality score and the majority of studies falling below the mode. Recommendations regarding future studies in this area focus on ensuring representativeness, including more objective measures of dependent variable decision-making and using prospective designs.

Despite the questionable quality of some studies included in the review, a number of findings are instructive for the design of future interventions and research efforts. Eleven broad factors are identified and discussed, with quantitative results and qualitative results integrated in a meaningful and illuminating manner. Weighted in rank order of evidence, factors populated from the studies were: vaccine efficacy, safety, and characteristics; healthcare system trust; information needs; vaccine preventable disease threat; parenting and social context; logistics and inertia; demographics; non-official information source reliance; anticipated regret (and other similar decision criteria); physiological individual differences; and lifestyle factors as countermeasures to VPD threat.

An update to the original search found an approximate doubling of potentially relevant literature in the 5-year period of 2008–2012, compared to the 21-year period 1987–2007.

Presented by Dr Hal Willaby, Research Fellow, NCIRS