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The return of the flu – Expert Q&A

New Zealand is preparing itself against the arrival of influenza and other viruses as the country continues to reopen its borders this autumn.

The Government will launch its winter flu campaign on Friday. Director of Public Health Dr Caroline McElnay said the Ministry of Health was “very concerned” about low measles, mumps and rubella vaccination rates among children and is urgently working to increase them.

The SMC asked experts to comment on respiratory virus surveillance and non-Covid-19 childhood vaccinations.

Dr Andrea McNeill, Technical Lead Epidemiology, ESR, comments*:

How does influenza and other respiratory disease surveillance happen and how has it been affected by the COVID-19 pandemic?

“In New Zealand, respiratory illness surveillance is done in both community and in hospital settings. This provides an understanding of the severity and level of spread of respiratory viruses such as influenza, respiratory syncytial virus (RSV) and SARS-CoV-2 in New Zealand.

“The community surveillance for respiratory illness uses a variety of data sources including calls to Healthline, visits to general practices, testing for a range of viruses by sampling from a small number of cases that present to general practices and reporting of symptoms through flu tracking surveys.

“The COVID-19 pandemic response has impacted existing community respiratory virus surveillance systems, for example, the use of community testing centres has changed how patients interact with general practices in some areas.

“However, the pandemic response has also led to the development of new systems that could be further developed to enhance existing surveillance. For example, ESR is working with the Ministry of Health to develop a system for community sentinel respiratory virus surveillance. Sentinel surveillance means that a proportion of community services participate in collecting additional information to provide a better picture of community health. This system will be implemented in a phased approach as soon as possible, and will include the establishment of a national respiratory virus testing repository, which will allow us to monitor national testing rates for respiratory viruses.

“ESR will operate and analyse both community- and hospital-level surveillance on behalf of the Ministry of Health in 2022. Typically weekly reporting (including of flu tracking data) is provided during the winter illness season (May-September), however with the borders re-opening we will be starting to report earlier this year on ESR’s website in the next few weeks.

“People can sign up to take part in the weekly flu tracking survey.”

When do ESR experts think the flu will come back into the community?

“Influenza continues to circulate internationally, mostly at low levels currently, but we expect cases to be arriving at our border now. A few cases of influenza A have already been detected in New Zealand.”

Can several respiratory viruses be tested all at once? And if so, would this be helpful in the New Zealand context?

“It is possible to test for a range of respiratory viruses using one swab. However, this cannot be done with the current rapid antigen tests in use – these are designed to detect SARS-CoV-2 only.

“Part of the community sentinel surveillance system development work includes selecting a sample of patients with symptoms of influenza-like illness to have a swab for PCR testing for multiple respiratory viruses, including influenza and the SARS-CoV-2 virus, which causes COVID-19.”

No conflicts of interest declared.

*Note (5 April 2022): Dr McNeill’s initial comments published on 30 March 2022 were updated on 5 April 2022.

Dr Sarah Jefferies, Public Health Physician, ESR, comments*:

Is there anything unique about this season’s strains?

“Two common seasonal strains have mostly been circulating in the Northern Hemisphere during their winter – most commonly the influenza A(H3N2) strain, followed by the B/Victoria virus strain. Our Southern Hemisphere seasonal influenza vaccine, which is now available in New Zealand (free of charge for pregnant women, older people, Māori and Pacific people over 55, and those with certain medical conditions) contains components selected to provide protection against four common influenza strains, and includes a change from the Northern Hemisphere’s vaccine which is designed to provide better protection against the predominant A(H3N2) strain.

“Countries in the Northern Hemisphere also experienced unusually high levels of RSV infection at the end of 2021. RSV is a common seasonal virus that can cause serious respiratory illness, particularly in infants and young children. This unusual RSV activity is similar to that experience in June in New Zealand last year, which was likely the result of lower population RSV immunity due to COVID-19 control measures in 2020 and increasing population mobility, including fewer lockdowns and some quarantine free travel, in 2021. There is not currently a vaccine to protect against RSV.

“Vaccination is the best protection against serious illness from influenza, as well as COVID-19, and it is also important to keep practicing the other key hygiene measures which protect yourself, your whānau and friends from the spread of serious respiratory viruses. The Ministry of Health’s website is a great source for further information.”

No conflicts of interest declared.

*Note (5 April 2022): Dr Jeffries’ comments were added on 5 April 2022.

Dr Dianne Sika-Paotonu, Immunologist, Associate Dean (Pacific), Head of University of Otago Wellington Pacific Office, and Senior Lecturer, Pathology & Molecular Medicine, University of Otago Wellington, comments:

“It has been announced recently that vaccinated Australians will be able to enter Aotearoa New Zealand from mid-April, with vaccinated visitors from around the world able to come through on 1st May 2022.

“The definition for being fully vaccinated against COVID-19, ideally should now include a booster shot. Unvaccinated individuals have a higher risk of becoming sick and unwell from COVID-19, and passing on the SARS-CoV-2 virus to others and also becoming hospitalised when compared with those who have been vaccinated and received a COVID-19 booster dose. For those overseas travellers entering Aotearoa New Zealand who haven’t yet received a booster injection, the opportunity to get boosted should be strongly encouraged.

“Monitoring for new variants of the SARS-CoV-2 virus will be important moving forward particularly with further easing of border restrictions. This will be especially important for managing potential future outbreaks caused by any new variants of the SARS-CoV-2 virus arising overseas.

“While issues with unequal global COVID-19 vaccine coverage, availability, accessibility and distribution persist, and remain unaddressed, new variants of the SARS-CoV-2 virus will continue to develop and spread. Community spread will be rapid if any new SARS-CoV-2 variants are capable of evading protection given by currently-available COVID-19 vaccines.

“Although COVID-19 has been a key focus over the past two years, it is important to remember that all childhood vaccinations are still important. An issue of major concern has been the disruption to usual (non-COVID-19) childhood vaccine schedules in Aotearoa New Zealand due to the Covid-19 pandemic. This means, there is potential risk of a measles or whooping cough outbreak for example.

“As a result of the COVID-19 situation, there are also children and young ones in Aotearoa New Zealand who may have never been exposed to the influenza virus. A resurgence of influenza and the respiratory syncytial virus (RSV) could possibly occur.

“The strong demand for the paediatric COVID-19 vaccine for children, tamariki and tamaiki aged 5-11 years has been encouraging, however vaccination efforts must continue. Of those affected by the current outbreak in Aotearoa New Zealand, a total of 191,507, 32 per cent (nearly 1/3) were children, tamariki and tamaiki and rangatahi aged 19 years and under.

“This group has comprised of 13 per cent of all hospitalisations, with the majority of these in the 0-9 years of age. Of those children aged 5-11 years, 53.9 per cent of the general population have received their first COVID-19 vaccine dose, and for Māori and Pacific tamariki and tamaiki, vaccination levels for first doses are at 34.8 per cent and 47.0 per cent respectively.

“Although children are overall more likely to have mild or asymptomatic disease, children can still catch the virus and become unwell – and get better quickly, end up with long COVID-19, and for children and youth with underlying medical conditions, have a higher risk of serious illness and hospitalisation.

“Omicron continues to spread rapidly across Aotearoa New Zealand with different areas of the country peaking at different times. These high number of COVID-19 case numbers are continuing to place added strain and pressure on our health and other support systems in Aotearoa New Zealand.

“Even though COVID-19 vaccination levels have lifted across Aotearoa New Zealand, care and caution are still needed – especially for our vulnerable communities.”

No conflict of interest.