Seroprevalence of SARS-CoV-2-specific antibodies in Australia following the first epidemic wave in 2020: a national survey

Background

As of mid-2021, Australia’s only nation-wide COVID-19 epidemic occurred in the first six months of the pandemic. Subsequently there has been limited transmission in most states and territories. Understanding community spread during the first wave was hampered by initial limitations on testing and surveillance. To characterize the prevalence of SARS-CoV-2-specific antibody seroprevalence generated during this time, we undertook Australia’s largest national SARS-CoV-2 serosurvey.

Methods

Between 19 June-6 August 2020, residual specimens were sampled from people undergoing general pathology testing (all ages), women attending antenatal screening (20–39 years) and blood-donors (20–69 years) based on the Australian population’s age and geographic distributions. Specimens were tested by Wantai total SARS-CoV-2-antibody assay. Seroprevalence estimates adjusted for test performance were produced. SARS-CoV-2 antibody-positive specimens were characterized with microneutralization assays.

Results

Of 11,317 specimens (5132 general pathology; 2972 antenatal; 3213 blood-donors), 71 were positive for SARS-CoV-2-specific antibodies. Seroprevalence estimates were 0.47% (95% credible interval: 0.04-0.89%), 0.25% (0.03-0.54%) and 0.23% (0.04-0.54%), respectively. No seropositive specimens had neutralizing antibodies.

Conclusions

Australia’s seroprevalence was extremely low (<0.5%) following the only national COVID-19 wave thus far. These data and the subsequent limited community transmission highlight the population’s naivety to SARS-CoV-2 and the urgency of increasing vaccine-derived protection.

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.

"No jab, no pay": catch-up vaccination activity during its first two years

Objectives

To assess catch‐up vaccination of older children and adolescents during the first two years of the “No jab, no pay” policy linking eligibility for federal family assistance payments with childhood vaccination status.

Design, setting, participants

Cross‐sectional analysis of Australian Immunisation Register data on catch‐up vaccination of children aged 5 to less than 7 years before (January 2013 – December 2014; baseline) and during the first two years of “No jab, no pay” (December 2015 – December 2017), and of children aged 7 to less than 10 years and young people aged 10 to less than 20 years (“No jab, no pay” period only).

Main outcomes

Catch‐up vaccination rates for measles–mumps–rubella vaccine second dose (MMR2), by age group, Indigenous status, and socio‐economic status; catch‐up vaccination of children aged 5 to less than 7 years (third dose of diphtheria–tetanus–pertussis vaccine [DTPa3], MMR1), before and after introduction of “No jab, no pay”.

Results

The proportion of incompletely vaccinated children aged 5 to less than 7 years who received catch‐up DTPa3 was higher under “No jab, no pay” than during the baseline period (15.5% v 9.4%). Of 407 332 incompletely vaccinated people aged 10 to less than 20 years, 71 502 (17.6%) received catch‐up MMR2 during the first two years of “No jab, no pay”, increasing overall coverage for this age group from 86.6% to 89.0%. MMR2 catch‐up activity in this age group was greater in the lowest socio‐economic status areas than in the highest status areas (29.1% v 7.6%), and also for Indigenous than for non‐Indigenous Australians (35.8% v 17.1%). MMR2 catch‐up activity in 2016 and 2017 peaked mid‐year.

Conclusions

Linking family assistance payments with childhood vaccination status and associated program improvements were followed by substantial catch‐up vaccination activity, particularly in young people from families of lower socio‐economic status.

Lower immunity to poliomyelitis viruses in Australian young adults not eligible for inactivated polio vaccine

There are limited long-term data on seroprevalence of neutralising antibody (nAb) to the three poliovirus serotypes following the switch from oral polio vaccine (OPV) to inactivated polio vaccine (IPV). In Australia, combination vaccines containing IPV replaced OPV in late 2005. Using serum and plasma specimens collected during 2012 and 2013, we compared prevalence of nAb to poliovirus type 1 (PV1), type 2 (PV2) and type 3 (PV3) in birth cohorts with differing IPV and OPV eligibility from an Australian population-based sample. In the total sample of 1673 persons aged 12 months to 99 years, 85% had nAb against PV1, 83% PV2 and 67% PV3. In the cohort 12 to <18 years (eligible for 4 OPV doses, last dose 8-14 years prior), a significantly lower proportion had nAb than in the 7 to <12 year cohort (eligible for 3 OPV doses and an IPV booster, last dose 3-8 years prior) for all poliovirus types: [PV1: 87.1% vs. 95.9% (P = 0.01), PV2: 80.4% vs. 92.9% (P = 0.003) and PV3: 38.1% vs. 84.0% (P < 0.0001)]. These data suggest individual-level immunity may be better maintained when an OPV primary schedule is boosted by IPV, and support inclusion of an IPV booster in travel recommendations for young adults who previously received only OPV.

Australian rubella serosurvey 2012-2013: On track for elimination?

BACKGROUND

The World Health Organization has targeted rubella virus for elimination regionally. Australia was one of the first countries to implement a nationally funded rubella immunisation program, in 1971, and conducts regular national rubella serosurveillance studies. We aimed to estimate the seroprevalence of rubella-specific IgG antibody in the Australian population by age and sex in 2012-2013, to compare the results with three previous serosurveys conducted in 1996-1999, 2002 and 2007 and to estimate the effective reproduction numbers (R_n).

METHODS

This study used 2729 serum and plasma specimens, randomly selected from a specimen bank collected in 2012-2013 across Australia. Age groups included in the sample ranged from 1 to 49 years. Sera were tested for rubella-specific IgG-antibody using the Enzygnost anti-rubella IgG enzyme immunoassay and classified as positive, negative or equivocal according to rubella-specific IgG concentrations of >7 IU/ml, <3 IU/ml and 3-7 IU/ml, respectively.

RESULTS

The overall proportions seropositive, seronegative and equivocal for rubella-specific IgG were 92.1% (95% CI, 91.0-93.2), 6.7% (95% CI, 5.7-7.7) and 1.2% (95% CI, 0.8-1.6), respectively. The proportion of males seropositive was significantly lower than females in the 30-34 (83.1% vs. 96.8%, p = 0.003), 35-39 (86.1% vs. 96.3%, p = 0.02) and 40-44 (86.1% vs. 95.7%, p = 0.03) year age groups. R_n for rubella in 2012-2013 was estimated to be 0.33 (95% CI 0.28-0.39).

DISCUSSION

The 2012-2013 national serosurvey showed levels of rubella-specific IgG seropositivity in the Australian population are relatively high with no evidence of decrease compared to previous serosurveys conducted in 1996-1999, 2002 and 2007. The lower proportion of seropositive males aged 30-44 years likely reflects the initial immunisation program targeting females only. To our knowledge this study represents the longest period of serosurveillance following introduction of a nationally funded rubella immunisation program. The lack of evidence of decreasing rubella-specific IgG seropositivity is therefore reassuring for Australia and other countries with longstanding high vaccine coverage.

Evaluation of bacille Calmette-Guérin immunisation programs in Australia

bacille Calmette-Guérin (BCG) immunisation programs in Australia are funded and operated by the individual states and territories. In recent years BCG vaccine shortages have required use of unregistered products. We aimed to evaluate BCG immunisation programs in Australia, with particular reference to program implementation and national consistency.
 Methods: Between September and November 2015, 12 key stakeholders, representing Australian states and territories, completed surveys. We analysed BCG vaccination coverage data from the Australian Childhood Immunisation Register (ACIR), and data on adverse events following immunisation (AEFI) with BCG vaccine from the Therapeutic Goods Administration's Adverse Drug Reactions System, for 2001 to 2014.
 Results: Access to BCG vaccination varies between jurisdictions, with some states providing this only in major city locations. Analysis of ACIR data suggests significant differences in vaccine delivery between jurisdictions, but varying levels of under-reporting to the ACIR were also acknowledged. The rate of BCG AEFI appeared to increase between 2011 and 2014; however, these data need to be interpreted with caution due to small numbers, likely under-reporting of both numerator (AEFI) and denominator (vaccine doses administered), and the general increase in reporting of AEFI related to other vaccines in children over this period.
 Conclusions: BCG immunisation programs aim to prevent severe forms of tuberculosis in young children who live in or travel to high burden settings. A range of factors, particularly inconsistent vaccine supply are leading to low, variable and inequitable vaccine delivery across Australian jurisdictions. Improved BCG vaccination uptake and AEFI data quality are required for accurate monitoring of program delivery and vaccine safety - this is particularly important given the current need to use unregistered vaccines. Improved and consistent access to BCG vaccine is suggested to optimise equity for at-risk children Australia-wide.

Immunisation coverage annual report, 2014

This 8th annual immunisation coverage report shows data for 2014 derived from the Australian Childhood Immunisation Register and the National Human Papillomavirus Vaccination Program Register. This report includes coverage data for 'fully immunised' and by individual vaccines at standard age milestones and timeliness of receipt at earlier ages according to Indigenous status. Overall, 'fully immunised' coverage has been mostly stable at the 12- and 24-month age milestones since late 2003, but at 60 months of age, it has increased by more than 10 percentage points since 2009. As in previous years, coverage for 'fully immunised' at 12 months of age among Indigenous children was 3.7% lower than for non-Indigenous children overall, varying from 6.9 percentage points in Western Australia to 0.3 of a percentage point in the Australian Capital Territory. In 2014, 73.4% of Australian females aged 15 years had 3 documented doses of human papillomavirus vaccine (jurisdictional range 67.7% to 77.4%), and 82.7% had at least 1 dose, compared with 71.4% and 81.5%, respectively, in 2013. The disparity in on-time vaccination between Indigenous and non-Indigenous children in 2014 diminished progressively from 20.2% for vaccines due by 12 months to 11.5% for those due by 24 months and 3.0% at 60 months of age.

Adverse events following immunisation with bacille Calmette-Guérin vaccination: baseline data to inform monitoring in Australia following introduction of new unregistered BCG vaccine

In recent years there has been a global shortage of bacille Calmette-Guérin (BCG) vaccine and, from September 2012, unregistered vaccines have needed to be used in Australia (a Danish product initially until the end of 2015, and a Polish product used in some jurisdictions from early 2016). We examined rates and types of adverse events following immunisation (AEFI) with BCG vaccine reported to the Therapeutic Goods Administration between 2009 and 2014 in children aged less than 7 years. Reporting rates of AEFI with BCG vaccine increased from 87 per 100,000 doses (registered Sanofi Pasteur product) in 2009 to 201 per 100,000 doses (unregistered Danish Statens Serum Institute product) in 2014, with Victoria having the highest rate each year. Substantial variation between jurisdictions exists, suggesting differential reporting of BCG vaccine doses administered and/or BCG vaccine-related AEFI. The most commonly reported reactions were abscess (31%), injection site reaction (27%) and lymphadenopathy/lymphadenitis (17%). This study provides baseline data on BCG vaccine safety to inform surveillance. Given the current use of unregistered vaccines in the context of vaccine supply issues, improved recording of both administered BCG vaccine doses and the reporting of BCG vaccine-related AEFI are required to facilitate close monitoring of vaccine safety.

Chromium-cage complex as contrast agent in MR imaging--biodistribution studies of the [57Co]cobalt analogue

The synthesis and T1 and T2 relaxivities of the Cr(III)-(NH2)-Sar-cage complex is reported. An outer-sphere relaxation mechanism is postulated for the relaxivity of the complex. Tissue distribution studies in mice using a [57Co]cobalt analogue as a radioactive tracer showed that the complex is excreted rapidly in the urine. Some renal uptake of the complex is seen. Appreciable uptake of labelled cage complex was observed in 3-methylcholanthrene induced murine rhabdomyosarcoma.