More than four in every 10 people who tested positive for Covid-19 in the six weeks to mid-October were fully vaccinated against the disease, new official data shows.
The figures show the scale of so-called breakthrough infections among a population with high vaccination rates.
Almost 89 per cent of people aged 12 and over have been fully vaccinated.
Figures from the Health Protection Surveillance Centre, which collates data on the coronavirus disease, show that of 58,361 new cases between September 5th and October 16th, some 25,433 or 43.6 per cent were fully vaccinated.
There were 25,571 unvaccinated people among the cases, representing 43.8 per cent of cases.
The vaccination status was unknown in some 6,736 cases or 11.5 per cent.
Of the 25,433 fully vaccinated people, 9,775 or 16.7 per cent were self-reported as being jabbed and 15,658 or 26.8 per cent were checked through the Covax vaccination programme system.
"As the vast majority (90 per cent) of the adult population in Ireland is currently vaccinated, even with a highly effective vaccine, we expect to see more cases, hospitalisations, ICU admissions and deaths in this vaccinated group than the much smaller group who are unvaccinated," the HPSC said.
The State's chief medical officer Dr Tony Holohan said last week that vaccines were performing better than expected in preventing severe infection but not in preventing transmission.
“In truth, they are probably not performing as well as we might have hoped in terms of preventing transmission so there is an impact in transmission by and to people who are vaccinated but it is not as great as you might like it,” he said at last week’s Covid-19 briefing.
Dr Holohan said that vaccinations alone were “not going to be enough” to reduce transmission and that simple health measures such as hand washing were required to stop the virus spreading.
On Friday, the HPSC reported that of the 474 people whose deaths due to Covid-19 were notified between April 1st and October 23rd, 212 or 44.7 per cent were fully vaccinated.
Some 267 people had been vaccinated with at least one dose of a Covid-19 vaccine.
Of the 212 fully vaccinated people who died, 120 were male and 92 were female, while the median age was 81 years. Almost 73 per cent of the people had an underlying medical condition.
There were 55 deaths in October, 94 in September, 52 in August and 11 from April to July.
Imperial College London research published last week showed that fully vaccinated people can contract and pass on the Delta variant – the current dominant Covid-19 strain that is twice as transmissible as the original virus – in households but at lower rates that unvaccinated people.
The findings published in the Lancet medical journal found that the chance of contracting the Delta variant from someone in your home was 25 per cent for the fully vaccinated compared with 38 per cent if unvaccinated, but this protection began to wane three months after vaccination.
