A cross-sectional study of susceptibility to vaccine-preventable diseases among prison entrants in New South Wales

Sarah Larney, Denise L Monkley, Devon Indig and Stephen E Hampton
Med J Aust 2013; 198 (7): 376-379. || doi: 10.5694/mja12.11110
Published online: 15 April 2013


Objectives: To determine the prevalence of susceptibility to measles, mumps, rubella, varicella and hepatitis B virus (HBV) among New South Wales prison entrants and to compare results for prison entrants with those of a community sample.

Design and setting: Between 11 October 2010 and 24 October 2010, new entrants at seven adult correctional centres completed a cross-sectional survey and provided a venous blood sample.

Participants: All adults entering the correctional centres were eligible to participate, with 211 completing the survey (response rate 68%).

Main outcome measures: Serological evidence of immunity to measles, mumps, rubella, varicella and HBV. Prison data were compared with community data obtained from the 2007 Australian National Serosurveillance Program.

Results: Over half of the participants (106/204, 52%) were susceptible to HBV, followed by susceptibility to mumps (82/198, 41%), rubella (33/209, 16%), measles (27/203, 13%) and varicella (19/198, 10%). Having no history of drug injection was a significant predictor of susceptibility to measles, mumps and HBV. Prison entrants were significantly less likely than people in the community to be susceptible to varicella (10% versus 18%; risk ratio [RR], 1.9; 95% CI, 1.1–3.2) and HBV (52% versus 65%; RR, 1.3; 95% CI, 1.1–1.5).

Conclusions: Prison entrants are susceptible to a number of vaccine-preventable diseases. We recommend a cost–benefit analysis of implementing routine vaccination for measles, mumps, rubella and varicella and an exploration of options for improving uptake of HBV vaccination.


This study was undertaken as a NSW-only add-on to the triennial National Prison Entrants’ Bloodborne Virus and Risk Behaviour Survey.8 Both studies were approved by the Justice Health Human Research and Ethics Committee.

Data collection

All interviewers were trained in administering the questionnaire and accredited in venepuncture. Questionnaire items were related to sociodemographics, prior incarcerations, injecting drug use (IDU) and other risk behaviours. To protect participant confidentiality, questionnaires and venous blood samples were labelled using a coded identifier.

Blood samples were analysed at the Institute of Clinical Pathology and Medical Research, Westmead Hospital. Some samples were of insufficient volume to be tested for all target infections, resulting in varying sample sizes for each infection. Measles, mumps and varicella zoster virus-specific IgG antibody titres were measured using ELISA (enzyme-linked immunosorbent assay) kits (Enzygnost). Rubella IgG antibody titres were measured using microparticle enzyme immunoassays (Architect; Abbott Diagnostics). Samples were classed as antibody-positive, antibody-negative or equivocal in accordance with the test manufacturer’s standards. Participants with antibody-negative or equivocal results were considered susceptible to infection.

Hepatitis B core antibody (anti-HBc), hepatitis B surface antibody (anti-HBs) and hepatitis B surface antigen (HBsAg) were measured using microparticle enzyme immunoassays (Architect; Abbott Diagnostics). Participant results were classified as follows:

Comparison data

The prison data were compared with NSW data from the 2007 Australian National Serosurveillance Program (ANSP). The ANSP collects stored serum samples from public and private diagnostic laboratories in each Australian state and territory. The collected sera are tested for antibodies to a variety of infectious diseases, including those tested in the Vaccine Preventable Diseases Study (VPDS).9,10 The data provided by the ANSP were the number of individuals, broken down by sex and birth cohort, with positive, equivocal and negative results for measles, mumps, rubella and varicella antibodies, and serological markers of HBV. Susceptibility to each disease was defined in the same manner as the prison data.


Of 311 prison entrants approached to participate in the study, 211 (68%) completed the questionnaire and provided a blood sample. Participants were similar to non-participants in terms of Aboriginality and age. Women disproportionately declined to participate, comprising 3% of participants and 19% of non-participants.

Of the participant sample, 97% (204/211) were male, and 21% (44/211) identified as Aboriginal or Torres Strait Islander. The median age was 32 years (range, 17–79 years). Almost two-thirds of the participants (65%; 138/211) had previously been in prison, and 37% (75/202) had ever injected drugs (Box 1).

Hepatitis B

Just over half of participants (52%; 106/204) were susceptible to HBV infection (Box 1); 3% (6/204) had acute or chronic infection, and 45% (92/204) were immune. Susceptibility was significantly higher among participants who were entering prison for the first time (P = 0.005), and those with no history of IDU (P = 0.003). In multivariate analysis, no history of IDU remained a significant predictor of susceptibility to HBV infection (P = 0.03).

Among the 92 participants who were HBV immune, 36% (33/92; 16% of the total sample) had acquired immunity through prior infection, and 64% (59/92; 29% of the total sample) had vaccine-conferred immunity. Post-hoc sub-analyses were undertaken to identify correlates of vaccine-conferred immunity among those with HBV data. Participants with a history of IDU were significantly more likely than than those with no history of IDU to have been vaccinated, with 28/72 (39%) of those with a history of IDU having been vaccinated, versus 31/126 (25%) of those with no history of IDU (P = 0.03). There was no significant relationship between prior incarceration and vaccine-conferred immunity; 44/134 participants (33%) who had previously been incarcerated had been vaccinated, compared with 15/70 (21%) who were entering prison for the first time (P = 0.08). There was no significant relationship between prior incarceration and vaccine-conferred immunity when the analysis was restricted to participants with a history of IDU; 27/63 (43%) of IDU prisoners with a prior incarceration were vaccinated, compared to 1/9 (11%) of IDU prisoners entering prison for the first time (P = 0.07).


Our analysis shows that the proportion of NSW prison entrants who are susceptible to vaccine-preventable diseases varies widely with each disease. Although prisoners’ susceptibility was lower than that of the general community for some diseases, recent experience with measles in NSW has shown that there are sufficient numbers of susceptible prisoners for outbreaks to occur. Recent work suggests that vaccination coverage of more than 95% may be necessary for the prevention of measles outbreaks.11 Entry into custody is an opportune time to routinely offer vaccinations against these infectious diseases in order to ensure high levels of immunity across the prisoner population. Combination measles–mumps–rubella vaccine, varicella vaccine, and HBV vaccine are all well tolerated by individuals who have previously been infected or vaccinated; as such, all individuals with an uncertain infection and vaccination history and without contraindications can safely commence these vaccination schedules. To our knowledge, the costs and benefits of routine vaccination in correctional settings have not been evaluated — a cost–benefit analysis would be an appropriate next step in developing vaccination policies.

Birth cohort and Aboriginality were not significant predictors of susceptibility to our target diseases. Participants born outside Australia were less likely to be susceptible to mumps, likely reflecting greater exposure to wild virus in the country of birth. No history of IDU was significantly associated with susceptibility to measles, mumps and HBV. In the case of measles and mumps, it is not clear if this association is a result of higher vaccination rates or exposure to wild virus. For HBV, there was some evidence of higher levels of vaccination among inmates with a history of IDU compared with those without. Despite policies mandating that HBV vaccine be offered to all inmates, there was no association between prior incarceration and HBV vaccination. A clear opportunity exists to improve HBV vaccination coverage among NSW prisoners in general, particularly those who inject drugs. The largest increases in HBV vaccination coverage are obtained through routine vaccination of prison entrants rather than in repeated mass campaigns.12,13 Administering vaccine via an accelerated schedule (on the day of entry into prison, 7 days after entry, 21 days after entry and a 12-month booster) can increase the proportion of prisoners completing the vaccination schedule.14


Currently, the Australian immunisation handbook recommends influenza, hepatitis A and hepatitis B vaccinations for prisoners.16 Given the potential for respiratory-spread infectious diseases to spread rapidly within prisons and into the community, and the high rates of IDU and other bloodborne virus risk behaviours among prisoners, there are logical benefits to ensuring that prisoners have high rates of immunity to infectious diseases. As such, we recommend a cost–benefit and feasibility analysis of implementing routine vaccination for measles, mumps, rubella and varicella, and exploration of options for improving uptake of HBV vaccination, such as accelerated schedules.

1 Demographic and behavioural characteristics and susceptibility to measles, mumps, rubella, varicella and hepatitis B virus among 211 prison entrants in New South Wales

Susceptibility (proportion of sample tested*)

All participants





Hepatitis B


211 (100%)

27/203 (13%)

82/198 (41%)

33/209 (16%)

19/198 (10%)

106/204 (52%)



204 (97%)

27/196 (14%)

78/191 (41%)

33/202 (16%)

19/191 (10%)

103/200 (52%)


7 (3%)


4/7 (57%)



3/4 (75%)

Indigenous status


44 (21%)

6/42 (14%)

19/38 (50%)

7/42 (17%)


17/40 (43%)


167 (79%)

21/161 (13%)

63/160 (39%)

26/167 (16%)

19/156 (12%)

89/164 (54%)

Birth cohort

< 1968

35 (17%)

3/32 (9%)

13/35 (37%)

4/35 (11%)

3/35 (9%)

19/35 (54%)


62 (29%)

3/57 (5%)

19/57 (33%)

10/61 (16%)

4/56 (7%)

27/57 (47%)


77 (36%)

12/74 (16%)

32/73 (44%)

12/76 (16%)

7/73 (10%)

42/76 (55%)

> 1989

37 (18%)

9/37 (24%)

18/33 (55%)

7/37 (19%)

5/34 (15%)

18/36 (50%)

Country of birth


163 (77%)

23/157 (15%)

71/154 (46%)

27/161 (17%)

13/154 (8%)

85/157 (54%)


48 (23%)

4/46 (9%)

11/44 (25%)

6/48 (13%)

6/44 (14%)

21/47 (45%)


Year 10 or less

149 (71%)

24/143 (17%)

63/137 (46%)

24/148 (16%)

12/139 (9%)

78/146 (53%)

Year 11 or greater

62 (29%)

3/60 (5%)

19/61 (31%)

9/61 (15%)

7/59 (12%)

28/58 (48%)

First time in prison


138 (65%)

20/132 (15%)

53/129 (41%)

22/136 (16%)

11/128 (9%)

60/134 (45%)


73 (35%)

7/71 (10%)

29/69 (42%)

11/73 (15%)

8/70 (11%)

46/70 (66%)

Ever injected drugs§


127/202 (63%)

21/125 (17%)

59/122 (48%)

18/126 (14%)

10/119 (8%)

75/126 (60%)


75/202 (37%)

4/70 (6%)

21/68 (31%)

12/74 (16%)

8/71 (11%)

27/72 (38%)

* Sample size varies with each disease because some samples were of insufficient volume to be tested for all target infections. P < 0.05 using χ2 test. P < 0.05 in multivariate logistic regression models with participant characteristics as independent variables. § Data were missing for nine participants.

Received 16 July 2012, accepted 29 October 2012

  • Sarah Larney1,2
  • Denise L Monkley2
  • Devon Indig2,1
  • Stephen E Hampton2

  • 1 University of New South Wales, Sydney, NSW
  • 2 Justice Health and Forensic Mental Health Network, Sydney, NSW



The VPDS was funded by the Justice Health and Forensic Mental Health Network. We thank the staff of the Population Health stream of Justice Health for conducting the VPDS and for providing additional information to help with preparation of this manuscript; the Institute of Clinical Pathology and Medical Research for serological testing of VPDS samples; and the National Centre for Immunisation Research and Surveillance for providing the Australian National Serosurveillance Program data.

Competing interests:

All authors are current or former employees of Justice Health and Forensic Mental Health Network, which funded the study.

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