Photo: RNZ
A study based on millions of New Zealanders' health records shows vaccination continues to provide protection against Covid. Given how quickly the virus changes, different countries around the world are now using slightly different vaccines.
The United States has options targeting emerging lineages. The United Kingdom is targeting the variant that caused the last, big wave. Australia is hoping to roll out the same vaccine by November.
Aotearoa New Zealand, meanwhile, is relying on a shot made to target a variant last recorded in surveillance data in January.
But does this matter?
How effective are our current Covid vaccines?
The Covid family tree
SARS-CoV-2, the virus that causes Covid, has a propensity for big, evolutionary leaps. In 2022, Delta was replaced by Omicron as the dominant strain. On an individual level, Omicron was less dangerous, but more transmissible.
Omicron subvariants have circulated since then, largely thanks to advantageous spike protein mutations.
From Omicron came BA.2.86, nicknamed Pirola, and then JN.1. JN.1 made headlines just before Christmas and by March, it accounted for 98 percent of sequenced cases.
By autumn, ESR was tracking its descendants, referred to as "FLiRT" or "FLip" (based on the technical names for their mutations).
Photo: AFP
The public research organisation's latest Covid genomics insights report, from August, found KP.3 lineages made up 64 percent of sequenced cases and were expected to continue to dominate over the coming weeks. Also part of the FLiRT family, and akin to KP.3's sibling, KP.2 accounted for 19 percent, but was increasing.
From KP.3 were various sublineages (KP.3.1 and KP.3.1.1).
"At present no emerging lineage has a growth rate comparable to KP.3.1.1," the report said.
Science leader, genomics and bioinformatics Dr David Winter told RNZ the KP.3 family "is the clear leader", and that was consistent with international trends.
However, while there was evidence of "high [Covid] activity" in the United Kingdom and the United States, in New Zealand, the presence of the virus in wastewater and the number of hospitalisations was relatively low, Winter added.
The rolling seven-day average of hospital admissions with Covid at the end of August was 22, according to Te Whatu Ora. In January, that figure was just shy of 50.
Vaccine effectiveness
On Friday, the New Zealand Medical Journal published a study on the effectiveness of the Covid vaccines over time, using health data from more than five million New Zealanders.
The vaccinated cohort included everyone who received the Pfizer-BioNTech (Comirnaty) vaccine from late 2020 through to February, 2023. Most of the country's population received this vaccine.
The vaccines were found to protect against death from Covid over the study period and were most effective at preventing hospitalisation and infection in the initial months after each dose.
A second booster dose initially reduced hospitalisations by 82 percent, dropping to 49 percent after six months. Protection against infection dropped from 57 percent to 10 percent during the same period.
This short-term protection against infection and long-lasting protection against severe illness and death is consistent with other studies around the world.
The authors noted the risk of severe Covid and mortality increased with age, relative socio-economic deprivation, disability status, and comorbidity. Māori and Pacific peoples were also at higher risk.
Updated vaccines
In April, the World Health Organisation's technical advisory group on Covid vaccine composition said as the virus was expected to continue to evolve from JN.1, the use of a monovalent JN.1 lineage as the antigen in future formulations was recommended. In short: new vaccines should target the JN.1 lineage.
However, countries should not toss older vaccines, and vaccination "should not be delayed in anticipation of access to vaccines with an updated composition".
The European Medicines Agency also recommended boosters be updated to target the JN.1 variants.
Meanwhile, the United States' Food and Drug Administration in mid-June changed its strain recommendation for the 2024-25 Covid vaccines, from JN.1 to its descendant, KP.2.
Now, in the United States, there are three updated vaccines available: one from Moderna, one from Pfizer, and one from Novovax. The Moderna and Pfizer vaccines are both formulated to target KP.2, while the Novovax shot is formulated to target JN.1.
In July, health authorities in the United Kingdom approved Pfizer's JN.1 jab.
And on Wednesday, the ABC reported that Australia's national drug regulator was evaluating two JN.1 vaccines, from Moderna and Pfizer. Experts have said they should be available by November.
Epidemiologist Adrian Esterman, from the University of South Australia, told the ABC the new vaccines were were "clearly better matched" to the virus than Australia's existing XBB.1.5 shots - the shots New Zealand was still using.
Covid vaccines in NZ
Currently, the Pfizer vaccines are the only Medsafe-approved and funded vaccines available for use in New Zealand.
Covid vaccination remains free and available to eligible people aged six months and over. While additional doses are recommended from six months after a Covid infection or vaccine, they are only available to healthy people aged 30 and older.
Pfizer's XBB.1.5 monovalent vaccine became available in New Zealand in March, followed by a paediatric version of the vaccine in May.
Pharmac previously funded a Novovax vaccine for Covid, however neither New Zealand nor Australia approved its latest vaccine, Nuvaxovid XBB.1.5. In July, Novovax withdrew its application.
Medsafe's website shows Pfizer has submitted an application for Comirnaty JN.1 and its status remains: "Initial evaluation".
Medsafe group manager Chris James said the application was received in August, and was being evaluated "under priority".
However, approval from the regulatory body was just one step in the process for making a medicine available in New Zealand, he said in a statement to RNZ.
"This process includes decisions made by other agencies and by the supplier company, which makes it difficult to predict when a medicine may be made available."
Medsafe had not received an application from Moderna for its updated vaccine.
While there had been suggestions the older formulations of vaccines were less effective against JN.1 and its descendants, an article published last month by the Public Health Communication Centre said: "The virus evolves so rapidly that it is not possible to match each vaccine update to the current variants.
"Fortunately, vaccines generally hold up well against new descendant variants that differ only in minor ways, as is currently the case. Problems can arise with a major evolutionary shift as happened from Delta to Omicron."
Data from the recent "Omicron-dense period" suggests older vaccines were holding up "extremely well", epidemiologist and director of the PHCC Michael Baker told RNZ.
"You're much better to get a protective vaccine of any sort, than wait for a slightly better vaccine."