The short term safety of COVID-19 vaccines in Australia: AusVaxSafety active surveillance, February - August 2021.

OBJECTIVE: To assess the short term safety of the COVID-19 vaccines Comirnaty (Pfizer-BioNTech BNT162b2) and Vaxzevria (AstraZeneca ChAdOx1) in Australia. DESIGN: Prospective observational cohort study; online surveys by AusVaxSafety, a national active vaccine safety surveillance system, three and eight days after vaccination. SETTING, PARTICIPANTS: People aged 16 years or more who received COVID-19 vaccines at sentinel vaccination hubs, general practices, or Aboriginal Community Controlled Health Organisation clinics, 22 February - 30 August 2021. MAIN OUTCOME MEASURES: Primary outcome: proportion of respondents who reported any adverse event following immunisation (AEFI) 0-3 days after vaccination. SECONDARY OUTCOMES: proportions of respondents who reported specific adverse events or medical review for AEFI within seven days of vaccination; impact on usual daily activities; recovery. RESULTS: 4 851 480 people received COVID-19 vaccines at participating sentinel sites during the study period (25% of all COVID-19 vaccine doses administered in Australia to 30 August 2021). 3 035 983 people responded to both surveys (response rate, 62.6%); 35.9% of respondents reported one or more AEFI 0-3 days after Comirnaty dose 1, 54.7% after Comirnaty dose 2, 52.8% after Vaxzevria dose 1, and 22.0% after Vaxzevria dose 2. Local pain, fatigue, headache, and myalgia were the most frequently reported symptoms. After adjusting for demographic characteristics, vaccination site type, jurisdiction, and self-reported medical conditions, the odds of reporting any AEFI were higher for women than men (range of adjusted odd ratios [aORs], by vaccine and dose, 1.53-1.84), for people with a history of anaphylaxis (aOR range, 1.28-1.45), and for people reporting certain underlying conditions, including obesity (aOR range, 1.15-1.75), immunodeficiency (aOR range, 1.04-2.24), or chronic inflammatory disease (aOR range, 1.05-1.75). 0.9% of respondents sought medical advice in the three days following vaccination, most frequently after Comirnaty dose 2 (1.4%) and Vaxzevria dose 1 (1.2%). CONCLUSION: AusVaxSafety active surveillance affirms the short term safety profile of Comirnaty and Vaxzevria vaccines in a large population sample during the first six months of the Australian COVID-19 vaccination program.

Risk factors and disease severity in Australian infants aged under 6 months hospitalised with influenza 2011-2019.

AIM: Infants aged <6 months are vulnerable to severe influenza disease and no vaccine is approved for use in this age group. We aimed to describe the epidemiology, risk factors associated with severe outcomes and management of influenza in Australian infants aged <6 months. METHODS: Incident cases aged <6 months of laboratory-confirmed influenza were captured through two national active prospective sentinel hospital-based surveillance systems in Australia from 2011 to 2019, inclusive. Demographic and clinical features, disease risk factors and outcomes (intensive care unit (ICU) admission and length of stay) and oseltamivir use were analysed. The proportion of infant influenza hospitalisations and nosocomial cases among all hospitalisations were also reported. RESULTS: Of 680 hospitalised infants aged <6 months, 57.9% were male and 14.5% were Indigenous Australian. Median age was 2.6 months, 19.2% were born premature and 19.0% had a comorbidity, excluding prematurity. Overall, 77.9% had influenza A. Nosocomial cases accounted for 7.8%. ICU admission occurred in 14.7% and oseltamivir was prescribed for 18.8%. Factors associated with ICU admission included age <1 month (adjusted odds ratio (aOR) 3.95, 95% confidence interval (CI): 1.47-10.60), comorbidity (aOR 7.69, 95% CI: 4.04-14.64) and prematurity (aOR 2.60, 95% CI: 1.40-4.81). The proportion of infants with influenza among all infant hospitalisations ranged 1.0-2.6% in the 2019 influenza season. CONCLUSION: Infants aged <6 months, and particularly neonates, experience serious disease from influenza. This data underpins the need for preventative strategies such as maternal immunisation and continued investigation into the possibility of safe and efficacious vaccination prior to 6 months of age.

Seroprevalence of SARS-CoV-2-specific antibodies in Sydney after the first epidemic wave of 2020.

OBJECTIVES: To estimate SARS-CoV-2-specific antibody seroprevalence after the first epidemic wave of coronavirus disease 2019 (COVID-19) in Sydney. SETTING, PARTICIPANTS: People of any age who had provided blood for testing at selected diagnostic pathology services (general pathology); pregnant women aged 20-39 years who had received routine antenatal screening; and Australian Red Cross Lifeblood plasmapheresis donors aged 20-69 years. DESIGN: Cross-sectional study; testing of de-identified residual blood specimens collected during 20 April - 2 June 2020. MAIN OUTCOME MEASURE: Estimated proportions of people seropositive for anti-SARS-CoV-2-specific IgG, adjusted for test sensitivity and specificity. RESULTS: Thirty-eight of 5339 specimens were IgG-positive (general pathology, 19 of 3231; antenatal screening, 7 of 560; plasmapheresis donors, 12 of 1548); there were no clear patterns by age group, sex, or location of residence. Adjusted estimated seroprevalence among people who had had general pathology blood tests (all ages) was 0.15% (95% credible interval [CrI], 0.04-0.41%), and 0.29% (95% CrI, 0.04-0.75%) for plasmapheresis donors (20-69 years). Among 20-39-year-old people, the age group common to all three collection groups, adjusted estimated seroprevalence was 0.24% (95% CrI, 0.04-0.80%) for the general pathology group, 0.79% (95% CrI, 0.04-1.88%) for the antenatal screening group, and 0.69% (95% CrI, 0.04-1.59%) for plasmapheresis donors. CONCLUSIONS: Estimated SARS-CoV-2 seroprevalence was below 1%, indicating that community transmission was low during the first COVID-19 epidemic wave in Sydney. These findings suggest that early control of the spread of COVID-19 was successful, but efforts to reduce further transmission remain important.

Barriers to influenza vaccination of children hospitalised for acute respiratory illness: A cross-sectional survey.

AIM: To identify barriers to influenza vaccination of children hospitalised for acute respiratory illness in Australia. METHODS: A total of 595 parents of children hospitalised with acute respiratory illness across five tertiary hospitals in 2019 participated in an online survey. Multivariate logistic regression identified factors most strongly associated with influenza vaccination barriers. RESULTS: Odds of influenza vaccination were lower with lack of health-care provider (HCP) recommendation (adjusted odds ratio (aOR) 0.18; 95% confidence interval (CI): 0.08-0.38); if parents had difficulties (aOR 0.19; 95% CI: 0.08-0.47) or were 'neutral' (aOR 0.23; 95% CI: 0.06-0.82) in remembering to make an appointment; and if parents had difficulties (aOR 0.21; 95% CI: 0.07-0.62) or were 'neutral' (aOR 0.24; 95% CI: 0.07-0.79) regarding getting an appointment for vaccination. Odds were also lower if parents did not believe (aOR 0.27; 95% CI: 0.08-0.90) or were 'neutral' (aOR 0.15; 95% CI: 0.04-0.49) regarding whether the people most important to them would have their child/ren vaccinated against influenza. Children had lower odds of vaccination if parents did not support (aOR 0.09; 95% CI: 0.01-0.82) or were ambivalent (aOR 0.09; 95% CI: 0.01-0.56) in their support for influenza vaccination. Finally, lack of history of influenza vaccination of child (aOR 0.38; 95% CI: 0.18-0.81) and respondent (aOR 0.25; 95% CI: 0.11-0.56) were associated with lack of receipt of influenza vaccine before admission for acute respiratory infection. CONCLUSIONS: Assisting parents in remembering and accessing influenza vaccination and encouraging health-care providers to recommend vaccination may increase uptake.

Effectiveness of Acellular Pertussis Vaccine in Older Adults: Nested Matched Case-control Study.

BACKGROUND: Despite recommendations that older adults receive acellular pertussis vaccines, data on direct effectiveness in adults aged over 50 years are sparse. METHODS: A case-control study nested within an adult cohort. Cases were identified from linked pertussis notifications and each matched to 3 controls on age, sex, and cohort recruitment date. Cases and controls were invited to complete a questionnaire, with verification of vaccination status by their primary care provider. Vaccine effectiveness (VE) was estimated by conditional logistic regression, with adjustment for reported contact with children and area of residence. RESULTS: Of 1112 notified cases in the cohort, we had complete data for 333 cases and 506 controls. Among 172 PCR-diagnosed cases (mean age, 61 years), 11.2% versus 19.5% of controls had provider-verified pertussis vaccination, on average, 3.2 years earlier. Adjusted VE against PCR-diagnosed pertussis was 52% (95% CI, 15-73%), nonsignificantly higher if vaccinated within 2 years (63%; -5-87%). Adjusted VE was similar in adults born before 1950, presumed primed by natural infection (51%; -8-77%) versus those born 1950 or later who may have received whole-cell pertussis vaccine (53%; -11-80%) (P-heterogeneity = 0.9). Among 156 cases identified by single-point serology, adjusted VE was -55% (-177-13%). CONCLUSIONS: We found modest protection against PCR-confirmed pertussis among older adults (mean age, 61 years; range, 46-81 years) within 5 years after acellular vaccine. The most likely explanation for the markedly divergent VE estimate from cases identified by single-titer serology is misclassification arising from limited diagnostic specificity in our setting.

Population-Level Herd Protection of Males From a Female Human Papillomavirus Vaccination Program: Evidence from Australian Serosurveillance.

BACKGROUND: Australia instituted funded female human papillomavirus (HPV) immunization in 2007, followed by a targeted male vaccination program in 2013. To date, Australia is one of only several countries with a funded male HPV immunization program. In 2012-2013, we conducted a survey of HPV seroprevalence in males to assess whether or not a herd impact of female vaccination could be observed. METHODS: We conducted a cross-sectional study of de-identified residual diagnostic test serum samples from males aged 15-39 years from laboratories in 3 Australian states and calculated the proportion seropositive to HPV types 6, 11, 16, and 18. We compared type-specific results by age group against those from a baseline 2005 Australian HPV serosurvey. RESULTS: There were decreases in proportion seropositive for every HPV type across all age groups, many statistically significant. The largest decrease was observed for HPV-11, with decreases of 8- and 9-fold for ages 20-29 and 30-39 years, respectively. Despite substantial reductions in seroprevalence, at least 9% of males were seropositive for at least 1 of the 4 HPV types. CONCLUSIONS: This is the first serosurvey confirming broad population-level impact in males from female HPV vaccination. Our research may assist policy makers considering implementing HPV vaccination programs.

Paediatric Active Enhanced Disease Surveillance (PAEDS) annual report 2015: Prospective hospital-based surveillance for serious paediatric conditions.

INTRODUCTION: The Paediatric Active Enhanced Disease Surveillance (PAEDS) network is a 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). PAEDS data is used to better understand these conditions, inform policy and practice under the National Immunisation Program, and enable rapid public health responses for certain conditions of public health importance. PAEDS enhances data available from other Australian surveillance systems by providing prospective, detailed clinical and laboratory information on children with selected conditions. This is the second of the planned annual PAEDS reporting series, and presents surveillance data for 2015. METHODS: Specialist surveillance nurses screened hospital admissions, emergency department records, laboratory and other data, on a daily basis in 5 paediatric tertiary referral hospitals in New South Wales, Victoria, South Australia, Western Australia and Queensland to identify children with the selected conditions. Standardised protocols and case definitions were used across all sites. Conditions under surveillance in 2015 included acute flaccid paralysis (a syndrome associated with poliovirus infection), acute childhood encephalitis (ACE), influenza, intussusception (IS; a potential AEFI with rotavirus vaccines), pertussis and varicella-zoster virus infection (varicella and herpes zoster). Most protocols restrict eligibility to hospitalisations, ED only presentations are also included for some conditions. METHODS: : In 2015, there were 674 cases identified across all conditions under surveillance. Key outcomes of PAEDS included: contribution to national AFP surveillance to reach WHO reporting targets; identification of signals for Mycoplasma pneumoniae and parechovirus-related outbreaks (ACE surveillance); and demonstration of high influenza activity with vaccine effectiveness (VE) analysis supportive of vaccination. Surveillance for IS remains ongoing with any identified AEFIs reported to the relevant State Health Department; varicella and herpes zoster case numbers decreased slightly from previous years in older children not eligible for catch-up. Pertussis case numbers increased in early 2015 and analysis of cases in children aged <1 year demonstrated the importance of timely childhood and maternal immunisation. CONCLUSIONS: PAEDS continues to provide unique policy-relevant data on serious paediatric conditions using hospital-based sentinel surveillance.

Changing Patterns of Pertussis in a Children's Hospital in the Polymerase Chain Reaction Diagnostic Era.

OBJECTIVE: To assess changes in diagnostic practice and vaccine schedules for pertussis, we used culture-confirmation and clinical severity to compare pertussis cases at a single Australian tertiary pediatric hospital during relevant periods. STUDY DESIGN: We replicated the case ascertainment methods of a study reporting a 2-year epidemic period 1997-1999 (whole cell pertussis vaccine with 18-month booster, only culture available) to conduct a retrospective cross-sectional observational study over a 6-year period 2007-2012 (acellular pertussis vaccine, no 18-month booster, polymerase chain reaction and culture available). Cases were compared from case note review 2007-2012 (including prevalence of comorbidities) and published data 1997-1999. RESULTS: During 2007-2012, average annual hospitalizations in those aged < 6 months increased 2.3-fold (32.0 vs 14.0) and in those aged > 6 months by 5.1-fold (17.7 vs 3.5). Limited to culture-positive hospitalizations, there was no increase in those aged < 6 months (14.0 vs 14.5) contrasted with a 4.6-fold increase in those aged > 6 months (2.3 vs 0.5), despite increased annual culture requests (488 vs 188). In 2007-2012, significant comorbidities were documented in 41/72 (57%) hospitalized children aged ≥ 12 months vs 38/225 (17%) <12 months (OR 6.5, 95% CI 3.7-11.7). CONCLUSIONS: Increased cases of culture-positive hospitalized pertussis were limited to fully immunized children > 6 months of age, consistent with schedule changes. Significant comorbidities were common, making a booster dose at 12-18 months of age especially important.

Surveillance of adverse events following immunisation in Australia annual report, 2014.

This report summarises Australian passive surveillance data for adverse events following immunisation (AEFI) for 2014 reported to the Therapeutic Goods Administration for 2014 and describes reporting trends over the 15-year period 1 January 2000 to 31 December 2014. There were 3,087 AEFI records for vaccines administered in 2014; an annual AEFI reporting rate of 13.2 per 100,000 population. There was a decline of 5% in the overall AEFI reporting rate in 2014 compared with 2013. This decline in reported adverse events in 2014 compared with the previous year was mainly attributable to fewer reports following the human papillomavirus (HPV) vaccine as it was the 2nd year of the extension of the National HPV Vaccination Program to males. AEFI reporting rates for most vaccines were lower in 2014 compared with 2013. The most commonly reported reactions were injection site reaction (27%), pyrexia (18%), rash (16%), vomiting (9%), headache (7%), and syncope (5%). The majority of AEFI reports described non-serious events while 7% (n=211) were classified as serious. There were 5 deaths reported with no clear causal relationship with vaccination found.

Paediatric Active Enhanced Disease Surveillance inaugural annual report, 2014.

INTRODUCTION: The Paediatric Active Enhanced Disease Surveillance (PAEDS) network is a hospital-based active surveillance system employing prospective case ascertainment of selected uncommon vaccine preventable diseases and potential adverse events following immunisation (AEFI). PAEDS enhances other Australian surveillance systems by providing prospective detailed clinical and laboratory data for the same child. METHODS: Specialist surveillance nurses screen hospital admissions, emergency department records, laboratory and other data, to prospectively identify hospitalised children aged under 15 years in 5 paediatric tertiary referral hospitals in New South Wales, Victoria, South Australia, Western Australia and Queensland. Standardised protocols and case definitions are used across all sites. Conditions under surveillance include vaccine preventable diseases: acute flaccid paralysis, varicella, pandemic and seasonal influenza and pertussis, and potential AEFIs: febrile seizures and intussusception. PAEDS also conducts surveillance for acute childhood encephalitis. RESULTS: Since August 2007, PAEDS has recruited a total of 6,227 hospitalised cases in total, for all conditions. From January to December 2014, there were 1,220 cases recruited across all conditions. Key outcomes include: enhanced acute flaccid paralysis surveillance to reach World Health Organization targets; supporting varicella and influenza vaccination in children; confirmation of a known low risk of febrile seizures following the 1st dose of measles-mumps-rubella vaccine but no increased risk of febrile seizures after measles-mumps-rubella-varicella vaccine, and a slightly increased risk of developing intussusception 1-7 days after rotavirus vaccination in infants aged less than 3 months. Acute childhood encephalitis data facilitated rapid investigation and response to the enterovirus 71 outbreak in 2013-2014. CONCLUSIONS: PAEDS provides unique policy-relevant data. This is the first of planned PAEDS annual reports to Communicable Diseases Intelligence.

Evaluating the implementation of the 13-valent pneumococcal vaccine supplementary dose program in Australian primary health care settings.

BACKGROUND: The availability of new pneumococcal conjugate vaccines covering a broader range of serotypes, has seen many countries introduce these into their national immunisation program. When transitioning from 7-valent to 13-valent pneumococcal conjugate vaccines, Australia is one of a small number of countries that included a supplementary dose of the 13-valent pneumococcal conjugate vaccine to offer protection against additional serotypes to an expanded age group of children. An evaluation of the implementation and uptake of the 13-valent pneumococcal conjugate vaccine supplementary dose was undertaken in two local health districts (LHDs) in New South Wales, Australia. METHODS: A self-administered postal survey of immunisation providers in the Northern New South Wales and Mid North Coast LHDs. Trends in vaccine ordering were examined. Coverage was assessed using data from the Australian Childhood Immunisation Register (ACIR). RESULTS: Of the 177 surveys sent, 125 were returned (70%). Almost all providers (96%) were aware of the 13vPCV supplementary dose program though took an opportunistic approach to program promotion and parental reminders. Supplementary doses of 13vPCV were ordered for 37% of the eligible cohort, mostly in the program's first six months. Coverage as recorded on the ACIR was 27%, though was lower in older children and those not due for scheduled childhood vaccines. Of the children who received the 13vPCV supplementary dose, 3% received it at the same time as vaccines due at 12-months of age, and 44% at the time of those due at 18-months of age. CONCLUSION: Despite the high awareness of the program, reported coverage was lower than that for other PCV supplementary dose programs in Australia and internationally. This may be influenced by providers' largely opportunistic approach to implementation, under-reporting to the ACIR or vaccine uptake. Lessons learned from this evaluation are relevant for future time-limited childhood vaccination programs. Prior to commencement, providers should be informed about the importance of catch-up/supplementary vaccination for their patients and their active role in promoting this. They should also receive program information before parents. An understanding of parental reasons for non-receipt of time-limited childhood vaccines and evaluation of the effect of aligning supplementary (or catch up) vaccination programs with the NIP schedule would be useful to inform future programs.

Australian vaccine preventable disease epidemiological review series: pertussis, 2006-2012.

Despite pertussis vaccine being available since the 1940s and immunisation programs using combined diphtheria-tetanus-pertussis vaccine since the mid-1950s, pertussis has been the most commonly notified vaccine preventable disease in Australia over the past 20 years. Pertussis notification and hospitalisation data have been available nationally since 1993, and provide different perspectives for understanding epidemiological trends. This report follows on from a previous review of Australian pertussis epidemiology from 1995-2005 and summarises routinely collected notification, hospitalisation and mortality data for 2006-2012. During the latter 7-year period, which incorporated epidemics in all jurisdictions, and in which acellular vaccines (as opposed to whole cell vaccines) were used exclusively, the average annual notification rate was more than 2.8 times that of the previous decade. In contrast, hospitalisation and mortality rates remained similar. The pattern of age-specific notification rates changed substantially, with cases aged 15 years or over representing 93% of total cases in 2006, but only 58% by 2012; the steepest increases were seen in children 2-4 and 6-9 years of age. In South Australia, where acellular vaccines were introduced into the primary schedule 2 years earlier than in other jurisdictions except the Northern Territory, a peak in notifications among those aged 5-9 and 10-12 years was observed earlier. Likely contributors to both the overall increase in notifications and changes in age distribution include increased diagnostic testing and more rapid waning of effectiveness following vaccination with acellular compared with whole cell vaccines, exacerbated by cessation of the 18-month dose in the National Immunisation Program from 2003.

Intussusception risk and disease prevention associated with rotavirus vaccines in Australia's National Immunization Program.

BACKGROUND: Estimates of the risk of intussusception (IS) associated with currently licensed rotavirus vaccines (RV1 [Rotarix; GSK] and RV5 [RotaTeq; Merck]) diverge. Contemporaneous introduction of both vaccines in Australia enabled a population-based assessment of risk. METHODS: Confirmed cases of IS in infants aged 1 to <12 months were identified from national hospitalization databases, supplemented by active hospital-based surveillance, from July 2007 through June 2010. Vaccination histories were verified by the Australian Childhood Immunisation Register, which was also used to identify age-matched controls. Self-controlled case series and case-control methods were used to assess the risk of IS associated with both vaccines in prespecified periods after vaccination. The estimated burden of vaccine-attributable IS was compared with estimated reductions in gastroenteritis hospitalizations. RESULTS: Based on 306 confirmed cases of IS, the relative incidence of IS in the 1-7-day period after the first vaccine dose, was 6.8 (95% confidence interval, 2.4-19.0; P < .001) for RV1, and 9.9 (95% confidence interval, 3.7-26.4; P < .001) for RV5. There was a smaller increased risk 1-7 days after the second dose of each vaccine. The case-control analysis gave similar results. We estimate an excess of 14 IS cases and >6500 fewer gastroenteritis hospitalizations in young children annually in Australia after vaccine introduction. CONCLUSIONS: We found a similarly increased risk of IS after both vaccines, but the balance of benefits and risks at population level was highly favorable, a finding likely to extend to other settings despite varying incidence of IS and potentially higher morbidity and mortality from both gastroenteritis and IS.

Uptake of influenza vaccine by pregnant women: a cross-sectional survey.

OBJECTIVES: To determine influenza vaccination coverage among pregnant women in New South Wales, and factors associated with vaccine uptake during pregnancy. DESIGN, SETTING AND PARTICIPANTS: Quantitative self-administered survey of pregnant women, using a non-random, stratified sample from antenatal clinics at three demographically diverse hospitals in NSW during the influenza season of 2011. MAIN OUTCOME MEASURES: Self-reported influenza vaccine uptake while pregnant; and attitudes, barriers and facilitators to vaccine acceptance during pregnancy. RESULTS: Of 939 women approached, 815 participated (87%). Influenza vaccine uptake in pregnant women was 27%. Women who had received a recommendation to have the vaccine were 20.0 times (95% CI, 10.9-36.9) more likely to have been vaccinated. Forty-two per cent recalled receiving a recommendation to be vaccinated. Other factors associated with vaccination were study site, perceived infection severity, overall feelings toward vaccination during pregnancy, vaccine accessibility, and willingness to take up the vaccine if recommended. Concern about the baby's safety was negatively associated with vaccination (odds ratio, 0.5; 95% CI, 0.2-0.9), but 68% (95% CI, 63%-71%) of women who expressed concern agreed they would have the vaccine if their health care professional recommended it. CONCLUSION: Recommendation from a health care provider is strongly associated with influenza vaccine uptake among pregnant women and can overcome their concerns about safety, but less than half the women surveyed reported receiving such a recommendation. Educational material targeting pregnant women and professional education and support for antenatal health care providers are needed to increase awareness and recommendation.

Pertussis in older adults: prospective study of risk factors and morbidity.

BACKGROUND: There is limited information on the incidence, morbidity and risk factors for pertussis in adults, particularly those aged over 65 years. METHODS: Population-based prospective cohort study of 263094 adults aged over 45 years (mean 62.8 years) recruited in the Australian state of New South Wales (the 45 and Up Study) between 2006 and 2008, and followed by record-linkage to laboratory-confirmed pertussis notifications, hospitalizations, and death records. The incidence of pertussis notifications and hospitalizations and relative risk (RR) of pertussis according to various participant characteristics was estimated using proportional hazards models. RESULTS: Over a total follow-up of 217524 person-years, 205 adults had a pertussis notification and 12 were hospitalized; the incidence rate was 94 (95% confidence interval [CI], 82-108) and 5.5 (95% CI, 3.1-9.7) per 100000 person-years, respectively. The incidence of a pertussis notification did not differ by age but hospitalization rates progressively increased (2.2, 8.5, and 13.5 per 100000 person-years in age groups 45-64, 65-74, and 75+ years, respectively; P(trend) = .01). After adjusting for age, sex, and other factors, adults with a high body mass index (BMI; RR=1.52; 95% CI, 1.06-2.19 for BMI 30+kg/m(2) vs BMI <25 kg/m(2)) and with preexisting asthma (RR=1.64; 95% CI, 1.06-2.55 compared to those without asthma) were more likely to be notified. CONCLUSIONS: Adults older than 65 years are more likely to be hospitalized for pertussis than those aged 45-64 years. Obesity and preexisting asthma were associated with a higher likelihood of pertussis notification. These findings suggest that pertussis vaccination would be particularly important for adults with these characteristics.

Australian vaccine preventable disease epidemiological review series: measles, 2012-2019.

Background: Data sources, relevant to measles epidemiology from 2012 to 2019, were reviewed in the context of Australia's certification, by the World Health Organization in 2014, of the elimination of measles. Methods: Data on measles notifications, hospitalisations, and deaths were obtained from the National Notifiable Diseases Surveillance System, the National Hospital Morbidity Database, and the Australian Coordinating Registry. Data were analysed by age group, state/territory, Aboriginal and Torres Strait Islander status, genotype, place of acquisition, source of infection (importation status), and vaccination status. Results: Between 2012 and 2019, there were 1,337 measles notifications (average annual notifications 0.7 per 100,000 population per year) and 425 hospitalisations with measles as principal diagnosis (0.3 per 100,000 population per year) were recorded. The highest annual notification rate was in 2014, when the rate in the Northern Territory was 21.4 per 100,000 population per year. Although notification and hospitalisation rates were highest in infants < 12 months (respectively 5.8 and 2.1 per 100,000 population per year), people aged 10 to 39 years (10-19y: 272 notifications; 20-29y: 347; 30-39y: 266) accounted for 66% of notified cases. Of cases with a known vaccination status, only 20/169 (11.8%) of those aged 1-9 years had received at least one dose of measles-containing vaccine, compared with 215/571 (37.7%) of those aged 10-39 years. Persons born before 1966 (at least 47 years of age during the study period) are likely to have immunity from wild-type measles infection and had the lowest notification rates in each year. Of notified cases, 98.1% were imported or import related, and of the 900 measles viruses genotyped, D8 and B3 accounted for 89.1%. Conclusion: This review's findings of low measles incidence, in the presence of robust surveillance and high two-dose measles vaccination coverage, provide evidence of continued elimination of endemic measles in Australia, with almost all cases imported or epidemiologically linked to an imported case. Most cases eligible for vaccination are unvaccinated, which should remain the primary focus for prevention. Potential waning immunity in older age groups requires monitoring. Continued high population immunity and high-quality public health response to cases will be needed to maintain Australia's elimination status, particularly once international borders reopen.

Australian vaccine preventable disease epidemiological review series: diphtheria 1999-2019.

Background: Diphtheria is rare in Australia, but an increasing number of cases have been notified in recent years. Alongside notifications from 1999 to 2019, we analysed other relevant national data sources to evaluate trends over the past two decades. Methods: Diphtheria notifications (National Notifiable Diseases Surveillance System [NNDSS]), hospitalisations (National Hospital Morbidity Database [NHMD]) and deaths (Australian Bureau of Statistics and the Australian Coordinating Registry) were separately analysed by site of infection, age group, sex, state/territory, Aboriginal and Torres Strait Islander status, and vaccination status. Results: During the study period, eight (0.002 per 100,000 population per year) cases of respiratory diphtheria and 38 (0.008 per 100,000 population per year) cases of cutaneous diphtheria were recorded in the NNDSS, with 45/46 reported in the nine years since 2011. Corynebacterium diphtheriae accounted for 87% of notified cases, who had a median age of 31.5 years (respiratory diphtheria) and 52.5 years (cutaneous diphtheria); no respiratory diphtheria was notified in those under 15 years of age. A majority of the cutaneous diphtheria cases (27/38; 71%) were acquired overseas, as were 3/8 (38%) of the respiratory diphtheria cases. Rates of both presentation types were higher in Aboriginal and Torres Strait Islander people (respiratory: 0.007 per 100,000 population per year; cutaneous: 0.021 per 100,000 population per year) than were rates in the overall population. Queensland had the highest rate of notified respiratory cases (0.007 per 100,000 population per year), and the Northern Territory the highest rate of cutaneous notifications (0.043 per 100,000 population per year). There were 29 hospitalisations with a principal-diagnosis diphtheria code in the NHMD between 2002 and 2018, of which eight were designated as respiratory (0.002 per 100,000 population per year), eight as cutaneous (0.002 per 100,000 population per year), and 13 with an unknown site of infection. Among notified cases, two deaths were reported in unvaccinated people in Queensland. Conclusions: Although diphtheria remains rare in Australia, 45 cases were notified in the years 2011-2019, compared with one case between 1999 and 2010. Robust surveillance remains important to detect all cases. High immunity will need to be maintained across all age groups to prevent outbreaks, and travel and adult booster doses should be encouraged.

Australian vaccine preventable disease epidemiological review series: Pertussis, 2013-2018.

INTRODUCTION: Significant recent changes in Australian pertussis immunisation policy include the progressive introduction of funded pertussis immunisation programs for pregnant women, from late 2014 to mid-2015 at jurisdictional level and then under the National Immunisation Program from July 2018, and reintroduction of the 18-month booster dose in 2016. This study analyses pertussis notification, hospitalisation, and mortality data from 2013 to 2018 in the context of trends since 1995. METHODS: This study used data from the National Notifiable Diseases Surveillance System, the National Hospital Morbidity Database, and the Australian Coordinating Registry, for descriptive analysis of pertussis notifications, hospitalisations and deaths in Australia by Aboriginal and Torres Strait Islander (Indigenous) status from 2013 to 2018, examining trends between 1995 and 2012 at both the national and jurisdictional level. Incidence rate ratios (IRR) were utilised to compare pertussis incidence in infants aged < 2 months and 6-11 months for each year from the 2015-2018 (post-maternal-vaccination) period against the 2010-2013 (pre-maternal-vaccination) period. RESULTS AND DISCUSSION: Annual national all-age incidence of pertussis notifications between 2013 and 2018 was 63.6 per 100,000 population, 40% less than between 2006 and 2012. Between 2016 and 2018, infants aged < 2 months had the lowest notification rates of age groups < 5 years old, with the highest notification rates in pre-adolescents aged 9-11 years. Compared with the baseline period (2010-2013), the IRR for infants aged < 2 months decreased in each year during the post-maternal-vaccination period from 0.4 (95% confidence interval [95% CI]: 0.3-0.5) in 2015 to 0.1 (95% CI: 0.1-0.2) in 2018. For infants aged 6-11 months, the IRR was 0.9 (95% CI: 0.8-1.0) in 2015, 1.1 (95% CI: 1.0-1.2) in 2016 and declined to 0.7 (95% CI: 0.6-0.8) in 2017 and 2018. Notification and hospitalisation rates in Indigenous children were 3-8 times as high as rates in non-Indigenous children across all age groups < 5 years old. CONCLUSION: Pertussis remains the second most frequently notified vaccine preventable disease in Australia, after influenza, but dramatic decreases in incidence have been observed in infants too young to receive any doses of pertussis-containing vaccine.

Pertussis Disease and Antenatal Vaccine Effectiveness in Australian Children.

BACKGROUND: Population-level studies of severe pertussis extending beyond infancy are sparse, and none in the context of antenatal vaccination. We compared hospitalized pertussis cases from birth to 15 years of age before and after introduction of antenatal immunization. METHODS: Active surveillance of laboratory-confirmed pertussis hospitalizations in a national network of pediatric hospitals in Australia January 2012 to June 2019. Impact of maternal vaccination was assessed by vaccine effectiveness (VE) in cases and test-negative controls with <2 months of age and by before-after comparison of age distribution of cases. Among cases eligible for one or more vaccine doses, we examined proportions age-appropriately immunized and with comorbidities by age group. RESULTS: Among 419 eligible cases, the proportion <2 months of age significantly decreased from 33.1% in 2012 to 2014 compared with 19.6% in 2016 to 2019 when mothers of only 4 of 17 (23.5%) cases <2 months of age had received antenatal vaccination. VE was estimated to be 84.3% (95% CI, 26.1-96.7). Across all years (2012-2019), of 55 cases 4-11 months of age, 21 (38%) had ≥2 vaccine doses, whereas among 155 cases ≥12 months of age, 122 (85.2%) had ≥3 vaccine doses. Prevalence of comorbidities (primarily cardiorespiratory) increased from 5 (2.1%) <6 months of age to 36 (24.2%) ≥12 months of age (P < 0.001), with 6/16 (38%) cases ≥12 months of age who required intensive care having comorbidities. CONCLUSIONS: Below the age of 12 months, prevention of severe pertussis will be maximized by high maternal antenatal vaccine uptake and timeliness of infant vaccine doses. Despite full immunization, we found children ≥12 months of age accounted for 27% of hospitalizations <15 years, with 24% having comorbities, suggesting new vaccine strategies, such as additional doses or more immunogenic vaccines, require evaluation.