Summary of national surveillance data on vaccine preventable diseases in Australia, 2012-2015

Paediatric Active Enhanced Disease Surveillance (PAEDS) 2019: Prospective hospital-based surveillance for serious paediatric conditions

Introduction

The Paediatric Active Enhanced Disease Surveillance (PAEDS) network is an Australian hospital-based active surveillance system employing prospective case ascertainment for selected serious childhood conditions, particularly vaccine preventable diseases and potential adverse events following immunisation (AEFI). This report presents surveillance data for 2019.

Methods

Specialist nurses screened hospital admissions, emergency department records, laboratory and other data on a daily basis in seven paediatric tertiary referral hospitals across Australia, to identify children with the conditions under surveillance. Standardised protocols and case definitions were used across all sites. In 2019, the conditions under surveillance comprised: acute flaccid paralysis (AFP; a syndrome associated with poliovirus infection), acute childhood encephalitis (ACE), influenza, intussusception (IS; a potential AEFI with rotavirus vaccines), pertussis, varicella-zoster virus infection (varicella and herpes zoster), invasive meningococcal and invasive Group A streptococcus diseases and two new conditions, Kawasaki disease and gram-negative bloodstream infections. An additional social research component continued to evaluate parental attitudes to influenza vaccination.

Results

PAEDS captured 2,701 cases for 2019 across all conditions under surveillance. Key outcomes of PAEDS included: contribution to national AFP surveillance to reach the World Health Organization reporting targets for detection of poliomyelitis cases; demonstration of high influenza activity in 2019 and influenza-associated deaths in ACE cases; identification of key barriers to influenza vaccination of children hospitalised for acute respiratory illness; reporting of all IS cases associated with vaccine receipt to relevant state health department; and showing a further reduction nationally in varicella cases. Enhanced pertussis surveillance continued to capture controls to support vaccine efficacy estimation. Invasive meningococcal disease surveillance showed predominance of serotype B and a reduction in cases nationally. Surveillance for invasive group A streptococcus captured severe cases in children. Monitoring of Kawasaki disease incidence and gram-negative bloodstream infections commenced.

Conclusions

PAEDS continues to provide unique policy-relevant data on serious paediatric conditions using sentinel hospital-based enhanced surveillance. Keywords: paediatric, surveillance, child, hospital, vaccine preventable diseases, adverse event following immunisation, acute flaccid paralysis, encephalitis, influenza, intussusception, pertussis, varicella zoster virus, meningococcal, group A streptococcus, Kawasaki, bloodstream infections.

Estimating pertussis incidence in general practice using a large Australian primary care database

BACKGROUND

While pertussis is notifiable in most countries, notifications typically underestimate the true pertussis burden. We explored the incidence of pertussis in general practice in Australia.

METHODS

Using MedicineInsight, a large longitudinal electronic medical record database of general practice (primary care) encounters which includes >1.5 million patients, we first defined a cohort of active patients and then used free-text search algorithms to identify patients with pertussis-related encounters. We defined and identified pertussis-related encounters in four patient categories: pertussis-associated (category 1), potential pertussis (category 2), epidemiologically-linked pertussis (category 3), and symptoms consistent with pertussis (category 4). Incident pertussis-related encounter rates per 100,000 active patients were calculated from Jan 2008 to Aug 2015.

RESULTS

Estimated mean annual pertussis incidence increased as definitions were expanded, from 94.3 (category 1 patients only) to 148.8 (categories 1+2+3 patients combined) per 100,000 active patients per year. Monthly time-series corresponding to the first three categories were highly correlated (Pearson's r > 90% for each pair), but each was poorly correlated with category 4. For categories 1+2+3, the highest incidence was among 0-4 and 5-9 year olds. Incidence was 30% higher in females than males (i.e. 184.5 vs 139.8 per 100,00 active patients for categories 1-3 patients combined). Pertussis-associated incidence (category 1) was similar to national pertussis notification rates. Categories 2 and 3 added 25% and 33%, respectively, on average relative to category 1 incidence. The estimated incidence from categories 1+2+3 together were on average 64% higher than national pertussis notification rates.

CONCLUSION

We provide comprehensive estimates of pertussis-related incidence in general practice (primary care), well in excess of notified pertussis incidence in Australia. This highlights the utility of MedicineInsight data in providing a greater understanding of the burden of medically-attended pertussis infections.

Australian mumps serosurvey 2012-2013: any cause for concern?

Objectives

To determine population-level immunity to mumps in Australia.

Methods

We tested randomly selected specimens from people aged 1-49 years using the Enzygnost anti-parotitis IgG enzyme immunoassay from an opportunistically collected serum bank in 2012-2013. Weighted estimates of the proportion seropositive and equivocal for mumps-specific IgG antibody were determined by age group and compared with two previous national serosurveys conducted in 2007-2008 and 1997-1998.

Results

Overall, 82.1% (95% CI 80.6-83.5%) of 2,729 specimens were positive or equivocal for mumps-specific IgG antibodies (71.1% positive [95% CI 69.4-72.9%]; 10.9% equivocal [95% CI 9.8-12.2%]). The proportion positive or equivocal was higher in 2012-2013 (82.1%) than in 2007-2008 (75.5%) and 1997-1998 (72.5%), but varied by age. The proportion positive or equivocal in 2012-2013 was above 80% for all age groups older than 1 year except for 30-34 year olds, corresponding to the 1978-1982 birth cohort previously identified as most likely to have missed out on a second MMR vaccine dose.

Conclusion

Seropositivity to mumps in 2012-2013 was well-maintained compared with previous serosurveys. Low mumps notifications over this period in Australia suggest an absence of community-based transmission of mumps infection in the general population, but recent outbreaks among Aboriginal adolescents and young adults in close-contact settings, despite high 2-dose MMR coverage, suggest that seroprotection may be insufficient in other similar settings in Australia.Seropositivity to mumps in 2012-2013 was well-maintained compared with previous serosurveys. Low mumps notifications over this period in Australia suggest an absence of community-based transmission of mumps infection in the general population, but recent outbreaks among Aboriginal adolescents and young adults in close-contact settings, despite high 2-dose MMR coverage, suggest that seroprotection may be insufficient in other similar settings in Australia.