Epidemiologist's warning for NZ about BA.2 sub-variant

A US epidemiologist has a warning for New Zealand with the country set to open its border in year three of the Covid-19 pandemic.

Dr Eric Feigl-Ding told Breakfast: "I would say be very careful, be very vigilant."

He had been asked if New Zealand runs the risk of importing BA.2 — a sublineage of the Omicron variant — at a rapid and therefore problematic rate.

The sub-variant BA.2 was found in New Zealand border workers and their close contacts in January. It was soon in the community and has now overtaken BA.1 in spread.

"We have to be vigilant. I know a lot of people think Covid is over, cases are falling, but while total cases are falling, BA.2 is rising," Feigl-Ding remarked.

He went on to say: "I hope New Zealand is protected. Don't just rely on two shot numbers, don't look at that, look at the booster protection numbers because the booster provides three times more protection against hospitalisation than just two shots alone. 90 per cent versus 70 per cent. I would really stress that. Don't just rely on border control, you have to mass test and additionally use boosters."

New Zealand's border is reopening in stages, with it fully reopening to visitors from anywhere in the world in October.

There were emotional scenes on Monday last week when the border reopened to Kiwis in Australia.

Most of New Zealand's MIQ facilities will be closed by the end of June.

"With New Zealand now reopening to the world without the requirement to isolate for most, there is a significantly reduced demand for MIQ. This of course means that we no longer need the number of facilities we currently have," Covid-19 Response Minister Chris Hipkins said on Thursday.

“The relative risk of people coming across the border now is actually lower than the people walking around in the community.”

In response to Feigl-Ding's warning, Hipkins later said on Breakfast he believes "it's safe for us [New Zealand]" to wind down MIQ and open the border.

Feigl-Ding also told Breakfast boosters were not optional if a person wanted full protection from BA.2.

He felt BA.2 was a "very different lineage" and said he would not personally even call it an Omicron sub-type.

Feigl-Ding explained BA.1 and 2 were more different than Delta is to the original Wuhan strain.

He said BA.2 has more than a dozen mutations and the worry is it has more infectious potential.

"BA.2 is about 30 per cent to double more contagious than even BA.1 and so that's the worry. It's extending this Omicron wave."

Feigl-Ding said it was spreading faster and had a higher attack rate in households — 14 per cent for BA.2 versus 10-11 per cent for BA.1. BA.2 has a 25 per cent higher attack rate.

"Without a booster, your two shots alone is only like 10 to 20 to 30 per cent efficacy against infection. In hospitalisation, it's only 70 per cent. But with the booster, you have about 78 per cent protection against infection and 90 per cent protection against hospitalisation. Which means you really, really need a booster. And I cannot stress that enough that there's simply not enough people getting it and people still feel boosters are optional. Well clearly with BA.2 it is not optional if you want full protection."