Repeatedly getting Covid doesn’t build immunity, ‘it’s more like accumulating damage’
Tuesday, 10 March 2026
Getting Covid-19 repeatedly puts people at risk of serious health damage, a public health expert is warning as the ninth wave of Covid-19 sweeps Aotearoa.
Leading vaccinologist Helen Petousis-Harris says there's not enough awareness of the impact of Covid-19 on overall health.
'What many people don't realise is that getting Covid repeatedly is not like building immunity, it's more like accumulating damage,' she says.
'Each infection raises your risk of long Covid and serious complications.'
It's been six years since New Zealand saw the rise of Covid-19, but experts suggest the country's collective immunity is waning. Wastewater analysis from PHF Science shows that the number of cases currently at its highest rate for more than six months and the latest Health New Zealand figures show there have been 50 hospitalisations and 19 deaths with the virus in the past week.
So, why are cases increasing and what can be done to reduce the risk?
Is there a new subvariant of Covid-19?
The current wave of Covid-19 is not a new subvariant of the virus, says Petousis-Harris, a University of Auckland associate professor. It's actually a variant of Omicron, which began spreading widely in 2022.
University of Otago professor of public health Michael Baker told RNZ that in the past four years there had been roughly two waves of Covid-19 per year.
Baker says the waves aren't seasonal - being equally distributed between winter and summer.
But this wave isn't following the pattern of a new subvariant emerging, which suggests a wane in immunity, he says.
The uptake in Covid-19 boosters had slowed, Baker says. For many, it has been quite some time since they were last infected and antibodies were dropping.
Are people still testing for the virus?
Petousis-Harris believes most people who have Covid-19 aren't testing to see if they have the virus.
She says that now, how many people have the virus is being monitored through wastewater testing.
No data is being kept on whether people are still testing themselves, Baker says, but he believes that many people won't be doing it as tests are no longer free. A Rapid Antigen Test, commonly known as a RAT test, costs around $5 depending on the retailer.
'I think that's a problem,' Baker says.
He urges anyone who has symptoms to get a test if they can afford it.
What are the symptoms?
The symptoms of Covid-19 have not changed in any significant way, Petousis-Harris says.
According to Health New Zealand, the main symptoms to look out for are a cough, sneezing or runny nose, fever, temporary loss of smell or altered sense of taste, sore throat, shortness of breath and fatigue.
Other less common symptoms include diarrhea, headache, muscle pain or body aches, nausea or vomiting and confusion or irritability.
Anyone with worsening symptoms should contact their doctor or Healthline.
People who have a weakened immune system, high-risk medical conditions, are over 65, pregnant, under the age of two or smoke are at higher risk of severe illness.
How can the risk of Covid-19 be reduced?
Booster vaccines are one of the best forms of protections available to the public, Petousis-Harris says.
While a booster vaccine will not stop a person getting infected by Covid-19, it will reduce the risk of getting seriously ill from the virus.
'The latest vaccine is well-matched to the variants driving this wave. It won't stop you getting infected, but it significantly cuts your risk of ending up seriously ill.'
She says anyone over 30 is eligible for free booster vaccines. Ideally, these should be taken every six months.
'That protection is real, but it fades, so staying up-to-date matters.'
Apart from staying up to date with boosters, Baker says self-isolation is important in reducing the spread of Covid-19.
He says anyone who has respiratory symptoms should stay home, whether they have been tested or not.