New Zealand's third wave of Covid-19 infections will likely reach its peak during the holiday period and stretch well into 2023.
The risk of infection is now the highest since June 2022 and continues to rise, driven by new, immune-evasive variants and the social mixing that comes with reduced pandemic controls, end-of-year events and holidays.
Reported cases have risen almost five-fold from a low point of about 1300 a day in September to more than 6000 a day now. Because of declining testing and reporting, the true number of infections is likely two to three times higher. Hospitalisations are also at their highest level since August and are rising quickly.
The risk of being exposed to the virus has increased markedly in all social settings. For example, in a small gathering of 10 people, the probability that one or more of the people attending has the virus has increased from 2-3 percent to more like 15 percent currently, and is likely to peak at about 20 percent.
For large gatherings of 100 people, this risk has risen from about 20 percent to more than 70 percent
The main message is that multiple meetings with different people add up to a lot of potential exposure to this virus, and the risk rises with the number of people and the prevalence of infection (as illustrated by this infographic). This combination is making the pre-Christmas period particularly high risk for New Zealanders.
The good news is that despite widespread Covid-19 infection there are simple ways you can protect yourself and others. A good first step is to recognise that all of us are vulnerable, even if we have been infected previously.
We estimate that more than half of current infections are reinfections, with the risk starting within a few weeks of each infection and increasing over time.
The most effective way to protect yourself from severe illness is being up to date with vaccines and boosters. A large number of eligible New Zealanders have still not had their third and fourth doses.
Anyone who has not been infected in the past three months should check whether they are eligible for a booster.
After that, it is important to recognise that Covid-19 transmits most effectively in crowded, close-contact, confined indoor environments. Try to avoid these situations. But if you are in packed shopping malls, on buses or planes, wear a respirator style mask (N95, KN95, P2, FFP2).
Such masks provide good protection for the wearer and those around them. They can reduce the risk of transmission by than 200-fold if both you and the people you are interacting with are wearing them.
When organising events or gatherings, remember that good ventilation is key to preventing transmission. Outdoors is best, but indoors can be relatively safe if well ventilated and not crowded. To add an extra layer of protection, especially when meeting vulnerable people, everyone can take a Rapid Antigen Test (RAT) before attending.
Te Pūnaha Matatini provides useful guidelines for organising safe events.
If you do get sick, it is vital to self-isolate and not go to work and social events for a minimum of seven days. RATs are still free, widely available and useful for showing when you are infectious. It can take a few days after the start of an infection to test positive on a RAT so continue to test after developing symptoms, or after a possible exposure event, even if you initially test negative.
It is also valuable to test at the end of the seven-day isolation period to check that you are no longer positive and potentially infectious to those around you.
Risk management is a partnership between individuals, their families, employers, venue operators, businesses and other organisations. The other partner is the government, which has a vital role in coordinating and guiding the public health response.
After three years, Covid-19 remains a pandemic. It has not yet transitioned to being a predictable endemic infection.
Genomic surveillance shows a succession of new subvariants replacing those that came before because of their improved ability to evade our immunity. In the last week, BA.5, which has been dominant for more than six months, has been replaced by a collection of BA.2.75 subvariants as the most common in New Zealand.
Ongoing viral evolution and waning immunity means people are being infected multiple times in a single year. Each infection carries a risk of serious illness and Long Covid.
The World Health Organization suggests the pandemic may cease to be a public health emergency of international concern next year. Regardless of its designation, it is likely to continue as a major health threat.
It has become the second leading cause of death in New Zealand this year (after ischaemic heart disease). Potentially, its largest health impact may be as a cause of long-term illness and disability through Long Covid. We still need measures to minimise both infections and severe outcomes.
Socialising with whānau, friends and colleagues is a highlight of the holiday season and vital for our health, wellbeing and enjoyment of life. At the same time, relatively small adjustments in how we do these things can help us enjoy the holiday period in relative safety.
*Michael Baker is Professor of Public Health at the University of Otago. David Welch is senior lecturer at the University of Auckland. Dion O'Neale is project leader at COVID Modeling Aotearoa; senior lecturer in the Department of Physics at the University of Auckland; and principal investigator at Te Pūnaha Matatini, University of Auckland.
**Disclosure statement: Michael Baker's employer receives funding for his research on Covid-19 and other infectious diseases from the Health Research Council of New Zealand (HRC) and the New Zealand Ministry of Health.
David Welch has received funding from HRC, MBIE, and ESR for Covid-19 modeling and genomic analysis.
Dion O'Neale's employer receives funding from the Health Research Council of New Zealand and from the New Zealand Ministry of Health for his research on Covid-19 modelling and the equity impacts of contagion modelling.