A study into the efficacy of the Covid-19 vaccination has measured Ministry of Health data from more than 5 million people. Photo: RNZ / Angus Dreaver
A major study into the effectiveness of Covid-19 vaccines in New Zealand has found the Pfizer injection provided sustained protection against death.
The collaborative research, which measured Ministry of Health data from more than 5 million people, found the vaccine was most effective at preventing hospitalisation and infection in the initial months after each dose.
Victoria University professor of population health Colin Simpson who is the study's co-author said the study used the identified data from New Zealand residents.
Infection, hospitalisations and death from Covid-19 were compared between people who were vaccinated and those who were not, he said.
"This is from a period from late 2020 to early 2023 and that was when the Omicron variant of Covid-19 was dominant."
It was found that Covid vaccinations were most effective in preventing negative outcomes in the initial months after they had been administered, he said.
"But between months four and six we saw a decline, a vaccine waning, which is actually expected - we've seen that in studies in other jurisdictions."
In terms of hospitalisations, after six months it wanes from about 80 percent after initial shot to about 57 percent after the first booster and to about 49 percent after the second booster, he said.
"Reassuringly it provides sustained effectiveness against death, so although we saw some drop-off, some waning [of effectiveness] it wasn't as much as for hospitalisation."
Simpson said further research was needed to follow up the individuals in the study because the study only covered the first and second boosters.
He advised anyone who was in a group that was susceptible to getting Covid-19 but who had not had a booster for six months to do so.
