Helen Aspasia Petousis-Harris is a New Zealand vaccinologist and associate professor in the Department of General Practice and Primary Health Care at the University of Auckland. She has been involved in research related to vaccination in New Zealand since 1998, with her main areas of focus being vaccine safety and effectiveness. Petousis-Harris has had a variety of lead roles in New Zealand and international organisations that focus on vaccination and is a regular media spokesperson in this field, especially during the COVID-19 pandemic.
Career From 1999 to 2002 Petousis-Harris was a researcher at the University of Auckland, working with the Immunisation Advisory Centre, a New Zealand-wide organisation based at the university. She continued in various roles at the centre, including honorary assistant research fellow and director of research from 1998. Between 2008 and 2011, she worked on her doctorate and wrote a thesis titled Factors associated with vaccine reactogenicity in school aged children and young adults following administration of two protein-based vaccines. Petousis-Harris was a senior lecturer at the Department of General Practice and Primary Health Care, University of Auckland from 2012 until February 2020 when she attained the position of associate professor.
In 2013 The Immunisation Advisory Centre (IMAC) set up the Vaccine Safety Expert Advisory Group, composed of "clinicians, scientists and policymakers who [had] either expertise and/or a professional interest in the safety of vaccines used in New Zealand", and Petousis-Harris has been a member of the group since it began.
Petousis-Harris became group director in 2018 of the Vaccine Datalink and Research Group, which is based at Auckland University and has a primary goal of "investigating the risks and benefits of vaccines using pharmacoepidemiologic approaches...[and]...vaccine development, vaccine immunology, and vaccine risk communication". Working with Steven Black, a "specialist in paediatric infectious diseases and vaccinology who had led major projects for the American Centres for Disease Control (CDC) and for the World Health Organization", Petousis-Harris established the internationally networked Global Vaccine Data Network (GVDN) in 2019. As of 2023 she remains co-director of GVDN, a role held since the beginning of the project.
Petousis-Harris was a member of the World Health Organization Global Advisory Committee on Vaccine Safety in 2017, being chair 2018–2020. and is a former member of the International Brighton Collaboration Science Board.
As from 2020, Petousis-Harris has been a member of the COVID-19 Immunisation Implementation Advisory Group (IIAG) which provides advice for the New Zealand Ministry of Health to implement the COVID-19 immunisation campaign, and part of the COVID-19 Vaccine Technical Advisory Group (CV TAG).
Areas of expertise
Pneumococcal vaccines A paper by Petousis-Harris in 2013 traced the history of the development of capsular polysaccharide vaccines against S. pneumoniae and noted the importance of this programme in reducing community-acquired pneumonia (CAP), bacterial meningitis, bacteremia and otitis media (OM), commonly known as middle ear infection. The same paper signalled concerns about ethnic inequalities in New Zealand with regard to hospital admissions due to this, and Petousis-Harris cited research that showed: an increase in acute hospital admissions for infectious diseases in general between 1989 and 2008 and most significantly for LRI. Hospitalisation for pneumonia and influenza almost doubled during this time period and age-standardised hospitalisations for Māori and Pacific increased progressively throughout the 1990s Petousis-Harris concluded that while vaccination was important for Maori and Pacific Island children, these inequalities may also result from factors such as overcrowding, poor housing and access to primary health care.
In 2015, research by Petousis-Harris and Colin Barber presented at the Annual Scientific Meeting of the Australasian Society for Infectious Diseases, showed preliminary figures that the rates of hospitalisation from invasive pneumococcal disease in children aged six years and under, had halved, with a 70% reduction for Maori and Pacific children. Prior to the conference, Petousis-Harris had drawn attention to the risks of children suffering permanent hearing loss if ear infections were not dealt with promptly by vaccination. In particular, along with her colleague, Colin Barber, she noted that compared to Pakeha children, almost twice as many Maori and Pacific Island children were at risk, with one-in-ten failing hearing tests when they started school. The study showed that vaccination helped reduce middle ear infections, and urged parents to monitor their children closely. Petousis-Harris earlier said the study demonstrated that the vaccine Synflorix reduced pneumonia, middle ear infections and hospitalisation from invasive pneumococcal disease (IPD).
Pertussis vaccination Pertussis, also known as whooping cough, is a highly infectious airborne respiratory disease that often shows as uncontrollable coughing causing breathing difficulties and can result in death, with infants and young children being particularly vulnerable. Because pertussis is known to be caused by the bacterium Bordetella pertussis, vaccination is effective. A paper co-authored in 2019 by Petousis-Harris, however, claimed: that in spite of vaccination having reduced mortality rates...an estimated 16 million pertussis cases and 195,000 child deaths [occurred globally] every year, with the greatest burden in low and middle-income countries. Furthermore, many high-income countries with high and stable vaccination rates, such as New Zealand, Australia and the United States, [had] an increasing pertussis burden and regular epidemics [were] not being preventedThe aim of this study was to investigate what could risk the effectiveness of pertussis vaccination, particularly for "infants between birth and six weeks of age born to mothers who received pertussis booster vaccinations during pregnancy and infants after the completion of the primary series (approximately five months old) to four years old". The authors were wanting to address gaps in knowledge due to the paucity of pertussis vaccination failure research by identifying who was most at risk of failure within the New Zealand primary immunisation schedule, and how common this failure was.
In 2016 Petousis-Harris and a team of researchers evaluated whether the switch from whole cell to acellular pertussis vaccine had contributed to the resurgence of pertussis disease in many countries which had made that change in the administration of the vaccine. The study assessed the duration of protection on 520,183 children using Infanrix, reporting on hospitalisation separately from notifications. The study found "a high level of protection with no reduction in VE (vaccine effectiveness) following both the primary course and the first booster dose. ...[and]...these findings [supported] a 3-dose primary course of acellular vaccine with no booster dose until 4 years of age".
Petousis-Harris took part in a cohort study in 2018 that explored safety outcomes in pregnant women in New Zealand who had received pertussis immunisation using Tdap vaccine. After conducting a retrospective observational study of women who received the vaccine during pregnancy, the authors concluded that there were no detectable adverse outcomes and were confident the study showed that Tdap could be administered safely to pregnant women. This was confirmed in another study on 793 women that concluded: "Vaccination with Tdap in pregnant women was well tolerated with no SAE likely to be caused by the vaccine." The impact on infants of Tdap vaccine in utero was evaluated in a 2019 study in which Petousis-Harris participated and the findings [supported] "the safety of administration of pertussis immunisation during pregnancy". Further research that monitored infants exposed to Tdap during pregnancy found data-based evidence that using Tdap at this time was effective in reducing pertussis in young children.
By March 2023 New Zealand faced a possible whooping cough epidemic. Petousis-Harris and Hannah Chisholm, an epidemiologist from Auckland University, explained how the usual cycles of herd immunity had been disrupted by COVID-19 restrictions, and with declining immunisation coverage, whooping cough along with measles, respiratory syncytial virus and influenza was likely to increase. Of particular concern was the effect on infants and young children, of whom around one third in New Zealand were said to be unvaccinated, and for Māori infants there was an even greater decline in coverage. The writers contended that infant fatalities could be prevented by high rates of vaccination by pregnant women and infants. It was also noted that other social and environmental factors that contributed to the spread of infectious such as housing conditions, needed to be dealt with by interventions and policies but this was a challenge because of an "under-resourced workforce, and a revised health system that [had] yet to demonstrate its worth".
Group B meningococcal vaccines In 1991, New Zealand began experiencing an epidemic of meningococcal disease and to control this a strain-specific vaccine (MeNZB) was developed, which in July 2004, resulted in a mass vaccination of people under 20 years of age. The mass campaign per se ended in 2006 but continued as a publicly-funded vaccine for infants up to 10 months. When it was decided to discontinue the vaccination in April 2008, Petousis-Harris co-authored a paper that aimed to "provide a background to this decision and explore the advantages, disadvantages and other considerations with regard to ceasing MeNZB vaccination". The article noted that the vaccine's excellent safety profile was reflected in the fact that it had protected up to 80% of New Zealanders under 20 years of age, and there appeared to be little benefit in continuing the programme. Concern was expressed, however, that in spite of the programme, meningococcal B disease in New Zealand was still above the levels from before the epidemic and it was important to acknowledge that the country had a "poor immunisation uptake compared to other nations...[and]...change could have to be made to the immunisation schedule". It was suggested that these changes would need to address the low rate of immunisation of Maori. Petousis-Harris was involved in a research project in 2009 that tracked how the MeNZB campaign had been reflected in media headlines. The data showed that "26 out of 51 headlines [were] inaccurate when compared with the article content (51%), with a further 6 being misleading (total of 61%)...[leading to a conclusion that]... to maintain public confidence, health planners constantly need to develop and review their health promotion messages and relationships with the media".
Responding to a news item on 23 April 2020 that suggested people in New Zealand aged 13 to 29 were highly at risk and needed to be vaccinated against meningococcal disease again, Petousis-Harris explained that these were the people who were under 5 years of age during the last epidemic, and agreed they needed another vaccination. She further noted that because of its flu-like symptoms it could be difficult to diagnose and progress quickly in "young adults living in crowded conditions and those with underlying health conditions...". Newshub, reporting on the same research cited in the article, claimed that there had been an 82% increase in the number of New Zealand infants contracting meningococcal disease in comparison to 2019. In response, Petousis-Harris stressed the importance of people being aware of when they were last vaccinated because protection was from 5 – 10 years, meaning young people and adolescents could be at risk.