22 Dec 2023

Four years on from Covid-19: What you need to know about new variants, vaccines, and staying safe

11:14 am on 22 December 2023
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Photo: 123rf.com

A new wave, a new vaccine, a new variant. Four years after Covid-19 was identified in Wuhan, China, it's still making headlines.

Aotearoa New Zealand's first case was reported on 28 February, 2020. A year later, the country was preparing for its largest immunisation roll out ever.

To date, more than 2.5 million cases have been reported and more than 3500 deaths have been attributed to Covid-19 in New Zealand.

By the year's end, 2023 is expected to total 1000 deaths, 12,000 Covid hospitalisations, and thousands of cases of debilitating long Covid, according to Otago University public health professor, Michael Baker.

And Covid is here to stay. It's no longer a public health emergency, according to the World Health Organisation, but an "established and ongoing health issue".

In August, the government scrapped the remaining Covid-19 restrictions.

But in the lead-up to the holiday season, wastewater testing and hospitalisations suggest New Zealand is experiencing a fifth wave of infections. Meanwhile, the WHO has named subvariant of Omicron, JN.1, a "variant of interest" due to its "rapidly increasing spread".

Where do we go from here?

The new variant

SARS-CoV-2, the virus that causes Covid, has a propensity for big, evolutionary leaps.

On an individual level, the Omicron variant - which replaced Delta as the dominant strain in early 2022 - is less dangerous than its predecessors. However, it's more transmissible.

As with earlier variant BA.2.86, nicknamed Pirola, JN.1 carries a high number of mutations on the spike protein. These spikes, protruding like needles from a pincushion, help the virus infect human cells.

"The subvariants are all in an evolutionary arms race," Professor Michael Baker says.

JN.1 made up about 3 percent of Covid cases globally in early November, and nearly 30 percent a month later, according to the WHO. But the organisation's overall risk evaluation of the variant is "low", because while it will likely cause an increase in cases, "available limited evidence does not suggest that the associated disease severity is higher".

In New Zealand, the variant was responsible for about 10-15 percent of infections according to the most recent sequencing and wastewater data - "so we are yet to feel its full impact", Covid-19 modeller Professor Michael Plank says.

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Photo: RNZ / Vinay Ranchhod

Peaks and troughs

Almost everyone in the country has some immunity to Covid. Most through a combination of vaccination and previous infection. And this provides good, long-term protection against severe disease, data shows.

But it doesn't stop infections and spread as the virus continues to evolve, leading to ongoing waves - peaks and troughs typical of an endemic disease.

"But [Covid] isn't like influenza and other seasonal, respiratory infections that virtually disappear over summer," Baker says. "It might take many years or decades for it to become a regular seasonal infection. Or it might never do that, we just don't know."

Human behaviour, including relaxation of protective measures and complacency, also plays a role,

He notes: "All Covid-19 infections carry the risk of long Covid. So it is still preferable to get your immunity from vaccine and avoid getting infected."

Baker and colleagues are calling for a comprehensive respiratory infection strategy, to reduce the health and economic impacts of Covid and other respiratory infections.

"This is a highly infectious disease occurring in waves that needs a systematic approach from government," Baker says. "We still need a health goal of minimising the number of Covid infections and re-infections."

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An updated Covid-19 vaccine will be available to New Zealanders from next winter. Photo: RNZ / Angus Dreaver, Nick Monro / AFP


As the virus evolves it becomes more resistant to the protection provided by the original Pfizer vaccine, the main vaccine used for primary doses in New Zealand. An updated version of the vaccine, called the bivalent vaccine, prompts the immune system to produce antibodies against spike proteins from both the original variant and Omicron. This is the main vaccine used for booster shots in New Zealand.

Despite the new, mutated subvariants, data suggests booster vaccines remain effective, particularly against severe disease, says Immunisation Advisory Centre director Professor Nikki Turner.

"Vaccination with a booster dose now could go a long way to helping slow the spread of disease over this summer and especially helping to protect those who are immunocompromised or elderly."

Still, experts have been calling for access to Pfizer's monovalent vaccine designed to target XBB.1.5, an Omicron descendant that emerged earlier this year. On Wednesday, Manatū Hauora Ministry of Health announced Medsafe has approved the vaccine and it will be available in time for winter, 2024.

Who gets boosted?

Everyone in New Zealand older than 5 can get a free Covid primary dose. If you're older than 16, you're also eligible for a booster.

Ministry deputy director Harriette Carr said the following groups in particular are recommended to get one:

  • people aged 65 and older,
  • Māori and Pacific people aged 50 and older,
  • those who have a medical condition that makes them severely immunocompromised (12 years of age and older),
  • pregnant people who have not had any booster dose previously, have co-morbidities, or have no history of previous COVID-19 infection,
  • residents of aged care facilities, and
  • people who were recommended to receive a booster in April 2023 but have not yet done so.

2024 and beyond

In the United States, Covid vaccination is recommended from 6 months of age. In New Zealand, the minimum age is 5 years, with exceptions for those at higher risk of severe illness from Covid.

Professor Peter McIntyre, head of Otago University's Department of Women's and Children's Health, says severe illness from Covid is rare in children and young people.

"Influenza is going to be a much more serious, ongoing problem for children born today than Covid," he says.

Respiratory syncytial virus (RSV) is also more likely to land a child in intensive care than Covid, he adds.

"Most paediatricians I've spoken to feel [Covid vaccination from 6 months] isn't warranted, at this stage."

Coming into 2024, we need better data on Covid cases, hospitalisations and deaths, to better inform public health strategies going forward, McIntyre says.

"I don't think it'll be practical to have restrictive policies to minimise infections.

"That model of stamping it out was successful before Delta got in in 2021, but it's not practical now."

And it's unclear whether it will continue to be cost-effective to offer booster shots to young, healthy people, he says.

What's clear, however, is the benefit of vaccinating at-risk populations: "If you're vulnerable or elderly, you need to hop on board with regular boosters."

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