Our Fourth Wave Of Covid-19 And Why We Should Care

Leading epidemiologist Professor Michael Baker says New Zealand is clearly experiencing a fourth wave of Covid-19 and health authorities should be reminding us about the benefits of vaccination and the value of measures to help reduce transmission.

Professor Baker and other public health experts from the University of Otago look at the numbers in the latest issue of the Briefing from the Public Health Communication Centre. These data indicate there could be up to 12,000 hospitalisations and more than 1,000 deaths this year from Covid-19.

This fourth wave is potentially driven by a rise in the XBB subvariant which has become dominant in the past two months. But other factors such as waning immunity and people spending more time indoors in autumn may be contributing to the numbers.

Professor Baker says this wave appears much smaller than the previous three, but it is still too early to say if it has peaked. “This pattern of small to moderate sized waves may indicate what we can expect to see with Covid-19 in coming years. But there are still major uncertainties given the potential for this virus to continue to evolve.”

Professor Baker says there are multiple reasons why we should be concerned about any increase in Covid-19, including that it is now a leading cause of mortality in New Zealand with 2,419 deaths last year.

“Covid-19 is also a major cause of hospitalisation, with more than 22,000 admissions in 2022. Infection can result in prolonged illness, including long Covid, and the virus is a source of inequalities with Māori and Pasifika markedly more likely to be admitted to hospital and die from this infection.”

The Briefing authors stress identifying new waves of infection is important for public health. It is a timely reminder this infection is still having a large health impact and there are actions to minimise those effects. Those actions include continuing vaccination and boosters, improving indoor ventilation, continuing to require 7-day isolation for those with Covid-19, encouraging mask-use in high-risk indoor environments, and using a more systematic approach to infection control in schools.

The Briefing also explores the multiple systems of surveillance NZ has for Covid-19 and suggests it could be time to transition to a “sustainable and enduring surveillance system for Covid-19, preferably one that also covers other important respiratory infections.” This need has become more critical now that the MoH has announcing that the proposed Covid-19 prevalence surveys will not be going ahead.

“A potential alternative is establishing sentinel surveillance of respiratory infections. For example, routinely testing a random sample of people attending specific health care settings such as general practices and emergency departments or community sites such as schools.”

The Briefing authors are Professor Michael Baker, Professor Nick Wilson, Dr John Kerr, and Dr Jennifer Summers.

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