The number of Covid-19 patients in hospital will rise to between 650 and 2,000 next month due to a massive surge of Omicron variant cases, public health officials have forecast.
The impact on critical care "could be even greater", with patient numbers exceeding 200, National Public Health Emergency Team (Nphet) member Prof Philip Nolan warned.
Even this estimate for critical care patients could go “way beyond that” if the variant turns out to be more transmissible or show more immune escape than officials have estimated, he said.
Omicron is expected to become the dominant variant in Ireland in the next four or five days, leading to a rapid increase in symptomatic infections. This will peak in January at between 8,000 and 20,000 cases a day, Prof Nolan said, depending on how much social mixing takes place over the Christmas period.
Nphet has drawn up a series of models for different growth scenarios around Omicron’s transmission advantage over previous strains of the virus, its ability to escape the protection provided by vaccines and the level of social mixing over the coming weeks.
Prof Nolan said the variant currently has a “window of opportunity” to spread in the population before widespread boosters are administered.
While case numbers will decline for a few more days because most cases still involved the Delta variant, “we’re going to be in real difficulty [with Omicron] very early, unless everything goes in our favour”.
Because so little is known about the new variant, it was very hard to tell what demand for healthcare it will cause, Prof Nolan told a media briefing on Friday.
“Everything has to go in our favour for this surge to be manageable. That means the risks of doing nothing or moderate intervention are far too high.”
Nphet’s most optimistic projection is for 650-1,000 Covid-19 cases requiring hospitalisation in early January. Its more, but not most, pessimistic projection is for 2,000 people requiring a hospital bed.
Prof Nolan said Omicron appeared in other countries to be spreading two to four times faster than Delta.
Omicron evades the protection vaccines provide against infection, but protection against serious illness remains, he said.
Two doses of AstraZeneca vaccine give "little protection" against becoming infected by the new variant but protection against disease remains significant.
Omicron reduces the protection against infection offered by mRNA vaccines (Pfizer and Moderna) by at least one-third, but a booster shot brings back protection to about 70 per cent and "probably" increases protection against severe disease, he said.
People who were previously infected by the original Wuhan virus or Alpha variant have lost half of their protection against the new variant.
Prof Nolan said he was “a bit worried” by data suggesting some of the protection vaccines give against serious illness could be lost. Even a small loss of protection against infection could translate into large numbers of people needing care.
He said it was possible Omicron causes a milder infection, and it isn’t more severe. But the difference appears to be marginal and would not be enough to compensate for it being more transmissible.
A further 3,628 Covid-19 cases were reported on Friday, officials said. There are 420 virus patients in hospital, including 105 in intensive care.
About 35 per cent of cases are now thought to involve Omicron, chief medical officer Dr Tony Holohan said, and the variant is set to become dominant within days.
Officials believe recent rises in case numbers among young adults, and in Dublin, are down to the onset of the Omicron variant.
Asked about travel curbs, Dr Holohan said their relative utility was reduced now that one-third of cases here were Omicron.
He said travel restrictions with southern African countries were being “stood back” as a result.
Prof Nolan said the peak of the Omicron wave would be much shorter due to the booster programme and would decline towards the end of January, but this would take a while to “work its way” through in terms of hospital cases.
Asked about the Cabinet’s rejection of a Nphet proposal to close hospitality at 5pm in favour of an 8pm curfew, Dr Holohan said it was less about the precise time than the clear intention to limit contact in high-risk environments.