Key points: 
* Covid-19 cases and household contacts to isolate for a week 
* Two negative rapid antigen tests required for household contacts 
* 250,000 Novavax vaccines here, people can book from tomorrow 

The isolation period for Covid-19 cases and their household contacts will be reduced from 10 to seven days from midnight Friday. 

And Covid-19 Response Minister Chris Hipkins has also announced the Novavax vaccine will be available for New Zealanders to book from tomorrow. 

Hipkins spoke just before the MInistry of Health announced there were 22,454 community cases and four deaths today. There were 742 people in hospital including 19 in ICU 

He said as case numbers increased, larger numbers of people needed to isolate and the reduced isolation time was due to high case numbers and wider impacts. 

"There needs to be a balance between effectively controlling the outbreak and the flow-on effect for business and essential goods and services such as transport and food supply," he said. 

"The most up to date public health advice is that there is a decline in infectiousness of Omicron over time, and that in most cases transmission occurs within seven days." 

The risk of reinfection of Covid-19 was very low in the first three months after having Omicron, he said. 

"For this reason, recovered cases will no longer need to self-isolate if they become a household contact within 90 days after having the virus. This is an increase from the current 28 days." 

The changes were a pragmatic decision, he said. 

Following a suggestion that opposition parties had called for these changes for some time, he said they tended to call for things "right now" but the reality was, if you wanted to follow an evidence-based approach, things do take time, he said. 

He said the evidence was indicating that seven days was the best timeframe to contain the risk while balancing up the need to get people back to work. 

"Our primary objective is to stop the chain of transmission as much as possible to manage the spread of Omicron. 

"Seven days isolation will break the vast majority of potential transmissions, while ensuring people can get back to work quicker and therefore reducing the impact on business operations." 

Household contacts will need to have a rapid antigen test at day 3 and day 7 of their isolation period, Hipkins said. 

If they become symptomatic they should also get a test, and if the result is positive, they are required to isolate for seven days from that point. 

If a person is isolating and still has symptoms after seven days, they are advised to stay home until 24 hours after symptoms resolve. 

He urged people to upload their RAT results, even if they were negative. 

Hipkins listed studies the government used to inform the changes, including from Japan and the Netherlands. 

On the country's Covid settings, Hipkins said he didn't expect to see any changes in the next few weeks. In terms of potentially regionalising a response, did say the Government had done that before and he wouldn't rule it in or out. 

On allowing positive Covid-19 health workers to return to work, Hipkins said a scenario where that could be justified, as an example, included a surgeon who, if they didn't perform a certain surgery, the patient would die. 

Hipkins said some people may have been using the unavailability of a vaccine to not get vaccinated. 

On New Zealand's border reopening, he said that was under review and more information wasn't expected to be "a long way off". 

Novavax vaccine 

"New Zealanders awaiting the arrival of Novavax to get vaccinated against Covid-19 will be able to make an appointment online or by phone from tomorrow," Hipkins also said. 

"A shipment of more than 250,000 Novavax Covid-19 vaccines (Nuvaxovid) has arrived in New Zealand and preparations are well advanced for some vaccination centres to be able to offer it next week. 

"Novavax will be available for people aged over 18. It requires two doses, with a three-week gap. It has not been approved as a booster dose. 

"While the Pfizer vaccine remains the preferred Covid-19 vaccine in New Zealand, Novavax is now available for those people who would prefer, or require, an alternative." 

Police investigating 

Meanwhile, police are investigating the possible sale of positive rapid antigen tests on social media. 

An Otago Facebook group user appeared to hawk the tests saying: ''Have you been overworked due to high demand and short staff? Feel like a 10-day break? 

"Well have I got the deal for you, 4 positive tests for sale (aka get out of jail free cards)." 

Epidemiologist Michael Baker said offering to sell or selling positive test results was tantamount to fraud and damaging to New Zealand's faith in the testing system. 

Just as Omicron has displaced or surpassed Delta, an Omicron subtype now appears to be taking over from another. 

The BA.2 subtype seems to be gaining the ascendancy – but a virologist says it's still not clear if it causes worse infection. 

University of Otago virologist Dr Jemma Geoghegan said any suggestion of greater disease severity with BA.2 wasn't translating to real-world observations. Photo / Supplied 

Otago University virologist Dr Jemma Geoghegan said any suggestion of greater disease severity with BA.2 wasn't translating to real-world observations. 

"I think it would be sensible to say that, if BA.2 was more severe, we would be seeing that play out because we know BA.2 has increased worldwide, and is now dominant in a lot of countries," she said. 

Australian epidemiologist Jodie McVernon yesterday told a business summit Omicron will bounce back over winter in a population whose virus defences have begun to wane.