In Elimination Settings, Measles Antibodies Wane After Vaccination but Not After Infection: A Systematic Review and Meta-Analysis.

BACKGROUND: We conducted a systematic review to assess whether measles humoral immunity wanes in previously infected or vaccinated populations in measles elimination settings. METHODS: After screening 16 822 citations, we identified 9 articles from populations exposed to wild-type measles and 16 articles from vaccinated populations that met our inclusion criteria. RESULTS: Using linear regression, we found that geometric mean titers (GMTs) decreased significantly in individuals who received 2 doses of measles-containing vaccine (MCV) by 121.8 mIU/mL (95% confidence interval [CI], -212.4 to -31.1) per year since vaccination over 1 to 5 years, 53.7 mIU/mL (95% CI, -95.3 to -12.2) 5 to 10 years, 33.2 mIU/mL (95% CI, -62.6 to -3.9), 10 to 15 years, and 24.1 mIU/mL (95% CI, -51.5 to 3.3) 15 to 20 years since vaccination. Decreases in GMT over time were not significant after 1 dose of MCV or after infection. Decreases in the proportion of seropositive individuals over time were not significant after 1 or 2 doses of MCV or after infection. CONCLUSIONS: Measles antibody waning in vaccinated populations should be considered in planning for measles elimination.

Knowledge and decisions about maternal immunisation by pregnant women in Aotearoa New Zealand.

BACKGROUND: Maternal vaccinations for influenza and pertussis are recommended in New Zealand to protect mothers and their infant from infection. However, maternal immunisation coverage in New Zealand is suboptimal. Furthermore, there is unacceptable inequitable maternal immunisation rates across the country with Maori and Pacific women having significantly lower maternal immunisation rates than those of other New Zealanders. METHODS: This research set out to explore what pregnant/recently pregnant Maori and Pacific women knew about immunisation during pregnancy and what factors influenced their decision to be vaccinated. A semi-structured interview guide was developed with questions focusing on knowledge of pertussis and influenza vaccination during pregnancy and decision-making. Maori and Pacific women aged over 16 years were purposively sampled and interviewed in Dunedin and Gisborne, New Zealand between May and August 2021. Interviews were analysed following a directed qualitative content approach. Data were arranged into coding nodes based on the study aims (deductive analysis) informed by previous literature and within these participant experiences were inductively coded into themes and subthemes. RESULTS: Not all women were aware of maternal vaccine recommendations or they diseases they protected against. Many underestimated how dangerous influenza and pertussis could be and some were more concerned about potential harms of the vaccine. Furthermore, understanding potential harms of infection and protection provided by vaccination did not necessarily mean women would choose to be vaccinated. Those who decided to vaccinate felt well-informed, had vaccination recommended by their healthcare provider, and did so to protect their and their infant's health. Those who decided against vaccination were concerned about safety of the vaccines, lacked the information they needed, were not offered the vaccine, or did not consider vaccination a priority. CONCLUSIONS: There is a lack of understanding about vaccine benefits and risks of vaccine-preventable diseases which can result in the reinforcement of negative influences such as the fear of side effects. Furthermore, if vaccine benefits are not understood, inaccessibility of vaccines and the precedence of other life priorities may prevent uptake. Being well-informed and supported to make positive decisions to vaccinate in pregnancy is likely to improve vaccine coverage in Maori and Pacific Island New Zealanders.

What Is the Evidence to Support a Correlate of Protection for Measles? A Systematic Review.

BACKGROUND: Many studies assume that the serologic correlate of protection from measles disease is 120 mIU/mL. We systematically reviewed the literature to examine the evidence supporting this correlate of protection. METHODS: We searched peer-reviewed and gray literature for articles reporting a measles correlate of protection. We excluded studies focusing on special populations, infants aged <9 months, and those using animal models or nonstandard vaccines or administration routes. We extracted and synthesized data from full-text articles that met inclusion criteria. RESULTS: We screened 14 778 articles and included 5 studies in our review. The studies reported either preexposure antibody concentrations of individuals along with a description of symptoms postexposure, or the proportion of measles cases that had preexposure antibody concentrations above a threshold of immunity specified by the authors. Some studies also described secondary antibody responses upon exposure. The variation in laboratory methods between studies made comparisons difficult. Some of the studies that assumed 120 mIU/mL as a correlate of protection identified symptomatic individuals with preexposure titers exceeding this threshold. CONCLUSIONS: Our findings underscore the scant data upon which the commonly used 120 mIU/mL measles threshold of protection is based, suggesting that further work is required to characterize the measles immunity threshold.

Risk Factors and Attack Rates of Seasonal Influenza Infection: Results of the Southern Hemisphere Influenza and Vaccine Effectiveness Research and Surveillance (SHIVERS) Seroepidemiologic Cohort Study.

Background: Understanding the attack rate of influenza infection and the proportion who become ill by risk group is key to implementing prevention measures. While population-based studies of antihemagglutinin antibody responses have been described previously, studies examining both antihemagglutinin and antineuraminidase antibodies are lacking. Methods: In 2015, we conducted a seroepidemiologic cohort study of individuals randomly selected from a population in New Zealand. We tested paired sera for hemagglutination inhibition (HAI) or neuraminidase inhibition (NAI) titers for seroconversion. We followed participants weekly and performed influenza polymerase chain reaction (PCR) for those reporting influenza-like illness (ILI). Results: Influenza infection (either HAI or NAI seroconversion) was found in 321 (35% [95% confidence interval, 32%-38%]) of 911 unvaccinated participants, of whom 100 (31%) seroconverted to NAI alone. Young children and Pacific peoples experienced the highest influenza infection attack rates, but overall only a quarter of all infected reported influenza PCR-confirmed ILI, and one-quarter of these sought medical attention. Seroconversion to NAI alone was higher among children aged <5 years vs those aged ≥5 years (14% vs 4%; P < .001) and among those with influenza B vs A(H3N2) virus infections (7% vs 0.3%; P < .001). Conclusions: Measurement of antineuraminidase antibodies in addition to antihemagglutinin antibodies may be important in capturing the true influenza infection rates.

Pneumococcal Conjugate Vaccines Turning the Tide on Inequity: A Retrospective Cohort Study of New Zealand Children Born 2006-2015.

BACKGROUND: Hospitalization rates for infectious diseases in New Zealand (NZ) children have increased since 1989. The highest burden is among Maori and Pacific children, and the most socioeconomically deprived. New Zealand introduced pneumococcal conjugate vaccine (PCV)7 in June 2008, PCV10 in 2011, and PCV13 in 2014. METHODS: A retrospective cohort study of NZ children aged <6 years between 2006 and 2015 was performed using administrative databases. Demographics and hospitalizations were linked to evaluate the impact of the PCV vaccination program on cases of invasive pneumococcal disease (IPD), all-cause pneumonia (ACP), and otitis media (OM), defined by ICD-10-AM codes, and to explore the effect by ethnicity and deprivation. RESULTS: Between 2006 and 2015, there were 640 children hospitalized with IPD, 26589 for ACP, and 44545 for OM. IPD hospitalizations declined by 73% between 2005 and 2015 for children <6 years of age, whereas ACP and OM declined by 8% and 25%, respectively. The highest rates for all diseases were among Maori and Pacific children and those from high deprivation. However, the declines were highest among Maori and Pacific children and those from socioeconomically deprived areas. IPD hospitalizations declined by 79% and 67% for Maori and Pacific children, respectively, between 2006 and 2015. ACP declined by 12% in Maori and 21% in Pacific children. OM declined by 51% in Maori children. CONCLUSION: In contrast to the increasing trend of hospitalization rates for infectious disease in New Zealand, the use of PCV appears associated with reductions in ethnic and socioeconomic disparities in hospitalization for IPD, ACP, and OM.

Perceptions of caregivers and providers regarding the potential introduction of the varicella vaccine to the childhood immunisation schedule in New Zealand: A qualitative exploratory study.

AIM: The varicella vaccine has been proposed to be added to the childhood immunisation schedule in New Zealand as the fourth injectable at the 15-month event. We sought to understand the perceptions of caregivers and health-care providers regarding the potential introduction of routine varicella vaccination. METHODS: A qualitative exploratory study was conducted using semi-structured interviews with caregivers and providers (N = 20) in Auckland. Key themes from the interviews were identified through thematic analysis using a combination of deductive and inductive coding. RESULTS: All of the participants were aware of varicella but levels of awareness varied among caregivers regarding the varicella vaccine. Participants expressed positive support towards universal varicella vaccination and a high intention to vaccinate if available as a routine vaccine. However, many concerns were raised about multiple injections at a single immunisation visit, and participants suggested alternative scheduling options. CONCLUSION: The results indicated a need to raise awareness among caregivers about the varicella vaccine, focusing on positive health beliefs about vaccination in terms of protecting the child's health and reducing the impact of a child getting varicella on the family. Health-care providers and government health authorities may play an important role in increasing positive health beliefs about the varicella vaccine. Should the varicella vaccine be introduced as proposed, our findings recommend an educational campaign to address both caregiver and provider concerns about multiple injections and how to manage alternative immunisation schedules. These insights may help inform national strategies for the proposed addition to increase acceptance of the varicella vaccination.

The challenges and opportunities of translating best practice immunisation strategies among low performing general practices to reduce equity gaps in childhood immunisation coverage in New Zealand.

BACKGROUND: Immunisation coverage rates vary considerably at the local level across New Zealand and challenges remain with effectively translating best available research evidence into public health practice. This study aimed to translate best practices from high performing general practices into strategies to improve childhood immunisation coverage among low performing practices. METHODS: An intervention study was undertaken of general practices with low immunisation coverage rates and a high percentage of the enrolled population being of Maori ethnicity. Intervention groups received customised action plans and support for a 12 month period while control groups received 'business as usual' support. Structured interviews were conducted with key informants from all participating practices to understand current aspects related to childhood immunisation delivery and surveys were conducted to understand how the intervention worked. Collected data were thematically analysed. RESULTS: Ten sites were randomised to either intervention (n = 6) or control group (n = 4). Positive aspects of childhood immunisation delivery included high prioritisation at the practice and staff being pro-immunisation and knowledgeable. Key challenges experienced included inaccurate family contact information and discrepancies with referral processes to other providers. Other challenges noted were building rapport with families and vaccine hesitancy. The action plans included various strategies aimed to improve processes at the practice, contact and engagement with parents, and partnership development with local service providers. CONCLUSIONS: Creating customised action plans and providing support to providers were considered as helpful approaches when attempting to improve childhood immunisation coverage rates. Our study supports the notion that one strategy will not solely by itself improve childhood immunisation rates and highlights the importance of having a toolkit of strategies from which to draw from.

Comparison of the Burden and Temporal Pattern of Hospitalisations Associated With Respiratory Syncytial Virus (RSV) Before and After COVID-19 in New Zealand.

BACKGROUND: Changes in the epidemiology of illnesses caused by respiratory syncytial virus (RSV) infection following the COVID-19 pandemic are reported. The New Zealand (NZ) COVID-19 situation was unique; RSV community transmission was eliminated with the 2020 border closure, with a rapid and large increase in hospitalizations following the relaxation of social isolation measures and the opening of an exclusive border with Australia. METHODS: This active population-based surveillance compared the age-specific incidence and seasonality of RSV-associated hospitalizations in Auckland, NZ, for 2 years before and after the 2020 border closures. Hospitalisation rates between years were compared by age, ethnicity (European/other, Maori, Pacific and Asian) and socioeconomic group (1 = least, 5 = most deprived). RESULTS: There was no RSV transmission in 2020. In all other years, hospitalisation rates were highest for people of Pacific versus other ethnic groups and for people living in the most deprived quintile of households. RSV hospitalisation rates were higher in 2021 and 2022 than in 2018-19. The epidemic peak was higher in 2021, but not 2022, and the duration was shorter than in 2018-19. In 2021, the increase in RSV hospitalisation rates was significant across all age, sex, ethnic and socioeconomic groups. In 2022, the increase in hospitalisation rates was only significant in one age (1- < 3 years), one ethnic (Asian) and one socioeconomic group (quintile 2). CONCLUSIONS: COVID pandemic responses altered RSV-related hospitalisation seasonal patterns. Atypical features of RSV hospitalisation epidemiology were the increase in rates in older children and young adults, which lessened in 2022. Despite these variations, RSV hospitalisations in NZ continue to disproportionately affect individuals of Pacific ethnicity and those living in more socioeconomically deprived households. Whilst future public health strategies focused on RSV disease mitigation need to consider the potential shifts in epidemiological patterns when the transmission is disrupted, these variances must be considered in the context of longer-standing patterns of unequal disease distribution.

Spatial and temporal transmission dynamics of respiratory syncytial virus in New Zealand before and after the COVID-19 pandemic.

Human respiratory syncytial virus (RSV) is a major cause of acute respiratory infection. In 2020, RSV was effectively eliminated from the community in New Zealand due to non-pharmaceutical interventions (NPI) used to control the spread of COVID-19. However, in April 2021, following a brief quarantine-free travel agreement with Australia, there was a large-scale nationwide outbreak of RSV that led to reported cases more than five times higher, and hospitalisations more than three times higher, than the typical seasonal pattern. In this study, we generated 1,471 viral genomes of both RSV-A and RSV-B sampled between 2015 and 2022 from across New Zealand. Using a phylodynamics approach, we used these data to better understand RSV transmission patterns in New Zealand prior to 2020, and how RSV became re-established in the community following the relaxation of COVID-19 restrictions. We found that in 2021, there was a large epidemic of RSV in New Zealand that affected a broader age group range compared to the usual pattern of RSV infections. This epidemic was due to an increase in RSV importations, leading to several large genomic clusters of both RSV-A ON1 and RSV-B BA9 genotypes in New Zealand. However, while a number of importations were detected, there was also a major reduction in RSV genetic diversity compared to pre-pandemic seasonal outbreaks. These genomic clusters were temporally associated with the increase of migration in 2021 due to quarantine-free travel from Australia at the time. The closest genetic relatives to the New Zealand RSV genomes, when sampled, were viral genomes sampled in Australia during a large, off-season summer outbreak several months prior, rather than cryptic lineages that were sustained but not detected in New Zealand. These data reveal the impact of NPI used during the COVID-19 pandemic on other respiratory infections and highlight the important insights that can be gained from viral genomes.

Impact of the COVID-19 related border restrictions on influenza and other common respiratory viral infections in New Zealand.

BACKGROUND: New Zealand's (NZ) complete absence of community transmission of influenza and respiratory syncytial virus (RSV) after May 2020, likely due to COVID-19 elimination measures, provided a rare opportunity to assess the impact of border restrictions on common respiratory viral infections over the ensuing 2 years. METHODS: We collected the data from multiple surveillance systems, including hospital-based severe acute respiratory infection surveillance, SHIVERS-II, -III and -IV community cohorts for acute respiratory infection (ARI) surveillance, HealthStat sentinel general practice (GP) based influenza-like illness surveillance and SHIVERS-V sentinel GP-based ARI surveillance, SHIVERS-V traveller ARI surveillance and laboratory-based surveillance. We described the data on influenza, RSV and other respiratory viral infections in NZ before, during and after various stages of the COVID related border restrictions. RESULTS: We observed that border closure to most people, and mandatory government-managed isolation and quarantine on arrival for those allowed to enter, appeared to be effective in keeping influenza and RSV infections out of the NZ community. Border restrictions did not affect community transmission of other respiratory viruses such as rhinovirus and parainfluenza virus type-1. Partial border relaxations through quarantine-free travel with Australia and other countries were quickly followed by importation of RSV in 2021 and influenza in 2022. CONCLUSION: Our findings inform future pandemic preparedness and strategies to model and manage the impact of influenza and other respiratory viral threats.

MMR vaccine coverage and associated factors among overseas-born refugee children resettled in Aotearoa New Zealand: a national retrospective cohort study.

Background: Refugee children may be under-immunised against common vaccine-preventable diseases due to a myriad of factors related to their migration journey. Methods: This retrospective cohort study explored the rates and determinants of enrolment on the National Immunisation Register (NIR) and measles, mumps and rubella (MMR) coverage among refugee children up to 18 years old who resettled in Aotearoa New Zealand (NZ) from 2006 to 2013. Univariate and multivariable logistic regression were conducted to determine associations. Findings: Of the cohort (N = 2796), two thirds of the children (69%) were enrolled on the NIR. Among this sub-cohort (n = 1926), less than one third (30%) were age-appropriately vaccinated with MMR. MMR coverage was highest among younger children and improved over time. Logistic modelling revealed that visa category, year of arrival, and age group were significant factors that influenced NIR enrolment and MMR vaccine uptake. Those arriving via asylum seeking, family reunification and humanitarian pathways were less likely to be enrolled and vaccinated compared to refugees who entered under the national quota programme. More recent arrivals and younger children were more likely to be enrolled and vaccinated compared to children who arrived in NZ longer ago and were older. Interpretation: Resettled refugee children have suboptimal NIR enrolment and MMR coverage rates which varied significantly by visa category, highlighting the need for immunisation services to better engage with all refugee families. These findings suggest that broad structural factors related to policy and immunisation service delivery may influence the differentials seen. Funding: Health Research Council of New Zealand (18/586).

Childhood vaccination uptake among children born in Aotearoa New Zealand based on parental nationality.

Migrants and refugees generally experience immunization inequities compared to their host populations. Childhood vaccination coverage rates are influenced by a complex set of interrelated factors, including child and parental nativity. Coverage rates for MMR, pertussis, and HPV vaccines were compared among children born in Aotearoa New Zealand (NZ) of overseas-born parents or NZ-born parents. A nationwide retrospective cohort study was conducted using linked, de-identified data. Logistic regression models examined the most influential factors contributing to differences in timely vaccine uptake. Of the total study population who had received all scheduled vaccines (N = 760,269), 32.9% were children of migrant parents. Children of migrant parents had higher rates of complete and timely uptake for MMR, pertussis, and HPV vaccinations compared to non-migrant children. NZ-born children of migrant parents were significantly more likely to receive MMR and pertussis-containing vaccines on-time compared to those of non-migrants. All included factors, except for the child's gender and parents' English ability, significantly influenced vaccine uptake. Among NZ-born children of migrant parents, additional logistic modeling found significant differences based on parental duration of residence, visa group, and region of nationality. Findings point to the importance of differentiating between parent versus child nativity when examining immunization coverage. While vaccination rates were higher for NZ-born children of migrant parents, compared to non-migrant parents, timely coverage rates across both groups were below national targets. Continued efforts are needed to improve timely immunization service delivery to address suboptimal and inequitable coverage.

A new national health system: the opportunity to address data quality issues in maternal immunisation coverage.

AIM: Maternal immunisation coverage is suboptimal in Aotearoa New Zealand. Our objective was to highlight discrepancies resulting from how maternal immunisation coverage for pertussis and influenza is measured in Aotearoa New Zealand. METHOD: A retrospective cohort study of pregnant people was undertaken using administrative datasets. Maternity and immunisation data from three sources (National Immunisation Register [NIR], general practice [GP], and pharmaceutical claims) were linked to determine the proportion of immunisation records not recorded in the NIR but captured in claims data, and to compare this with coverage data available from Te Whatu Ora - Health New Zealand. RESULTS: We found that while increasing numbers of maternal immunisations are being captured in the NIR, around 10% remain unrecorded on the NIR, but within claims datasets. CONCLUSION: Accurate maternal immunisation coverage data is important for public health action. Implementation of the whole-of-life Aotearoa Immunisation Register (AIR) is an important opportunity to improve completeness and consistency of maternal immunisation coverage reporting.

Continued mitigation needed to minimise the high health burden from COVID-19 in Aotearoa New Zealand.

In this article we review the COVID-19 pandemic experience in Aotearoa New Zealand and consider the optimal ongoing response strategy. We note that this pandemic virus looks likely to result in future waves of infection that diminish in size over time, depending on such factors as viral evolution and population immunity. However, the burden of disease remains high with thousands of infections, hundreds of hospitalisations and tens of deaths each week, and an unknown burden of long-term illness (long COVID). Alongside this there is a considerable burden from other important respiratory illnesses, including influenza and RSV, that needs more attention. Given this impact and the associated health inequities, particularly for Maori and Pacific Peoples, we consider that an ongoing respiratory disease mitigation strategy is appropriate for New Zealand. As such, the previously described "vaccines plus" approach (involving vaccination and public health and social measures), should now be integrated with the surveillance and control of other important respiratory infections. Now is also a time for New Zealand to build on the lessons from the COVID-19 pandemic to enhance preparedness nationally and internationally. New Zealand's experience suggests elimination (or ideally exclusion) should be the default first choice for future pandemics of sufficient severity.

Early childhood education staff are falling through a vaccination policy gap in New Zealand.

The recent COVID-19 vaccine mandate among early childhood education (ECE) staff highlights the important role ECE staff have in the transmission of infectious diseases. However, there are no data on general vaccine uptake for this group in New Zealand. Additionally, the importance of ECE staff vaccination as a strategy to prevent illness has been rarely promoted in the past, and recommendations for other vaccinations in this group are lacking. Here we present a section of data accessed from an ECE-sector employment survey of more than 4,000 teaching staff, which inquired into the immunisation status of respondents. The data indicated that self-reported immunisation coverage for whooping cough, hepatitis A, and hepatitis B among ECE staff was approximately 50%. Self-reported immunisation status was higher for measles, mumps, rubella, and chickenpox in this group. The findings highlight the need for more comprehensive vaccination policy and research in ECE settings.

Vaccine mandates in the time of Omicron.

Nil.

Evidence of suboptimal maternal vaccination coverage in pregnant New Zealand women and increasing inequity over time: A nationwide retrospective cohort study.

BACKGROUND: Adequate maternal vaccination coverage is critical for the prevention and control of infectious disease outbreaks such as pertussis, influenza, and more recently COVID-19. To guide efforts to increase vaccination coverage this study examined the extent of vaccination coverage in pregnant New Zealand women over time by area-level deprivation and ethnicity. METHODS: A retrospective cohort study was used consisting of all pregnant women who delivered between 01 January 2013 and 31 December 2018, using administrative health datasets. Outcomes were defined as receipt of influenza or pertussis vaccination in any one of the relevant data sources (National Immunisation Register, Proclaims, or Pharmaceutical collection) during their eligible pregnancy. Ethnicity was prioritised as Maori (NZ indigenous), Pacific, Asian, and Other or NZ European and deprivation was defined using New Zealand Index of Multiple Deprivation (IMD). RESULTS: Between 2013 and 2018, Asian women had the highest maternal vaccination coverage (36%) for pertussis, while Maori and Pacific women had the lowest, 13% and 15% respectively. Coverage of pertussis vaccination during pregnancy in low deprivation Maori women was 24% and 28% in Pacific women. This is in comparison to 30% and 25% in high deprivation Asian and European/Other women, respectively. Similar trends were seen for influenza. CONCLUSION: Between 2013 and 2018 maternal vaccination coverage increased for pertussis and influenza. Despite this coverage remains suboptimal, and existing ethnic and deprivation inequities increased. There is an urgent need to focus on equity, to engage and support ethic communities by creating genuinely accessible, culturally appropriate health services.

Climate change: the implications for child health in Australasia.

Children are particularly vulnerable to the health effects of climate change, the biggest global health threat of the 21st century. However, the worst effects on child health can be avoided, and well-designed climate policies can have important benefits for child health and equity. We call on child health professionals to seize opportunities to prevent climate change, improve child health and reduce inequalities, and suggest useful actions that can be taken.

Primary care practice and health professional determinants of immunisation coverage.

AIM: To identify primary care factors associated with immunisation coverage. METHODS: A survey during 2005-2006 of a random sample of New Zealand primary care practices, with over-sampling of practices serving indigenous children. An immunisation audit was conducted for children registered at each practice. Practice characteristics and the knowledge and attitudes of doctors, nurses and caregivers were measured. Practice immunisation coverage was defined as the percentage of registered children from 6 weeks to 23 months old at each practice who were fully immunised for age. Associations of practice, doctor, nurse and caregiver factors with practice immunisation coverage were determined using multiple regression analyses. RESULTS: One hundred and twenty-four (61%) of 205 eligible practices were recruited. A median (25th-75th centile) of 71% (57-77%) of registered children at each practice was fully immunised. In multivariate analyses, immunisation coverage was higher at practices with no staff shortages (median practice coverage 76% vs 67%, P = 0.004) and where doctors were confident in their immunisation knowledge (72% vs 67%, P= 0.005). Coverage was lower if the children's parents had received information antenatally, which discouraged immunisation (67% vs 73%, P = 0.008). Coverage decreased as socio-economic deprivation of the registered population increased (P < 0.001) and as the children's age (P = 0.001) and registration age (P = 0.02) increased. CONCLUSIONS Higher immunisation coverage is achieved by practices that establish an early relationship with the family and that are adequately resourced with stable and confident staff. Immunisation promotion should begin antenatally.