Data published by the UK Health Security Agency at the time of the claim suggested that with two doses, vaccine effectiveness against hospitalisation due to Omicron was 52%.

However, vaccine effectiveness against hospitalisation is not a measure of hospitalisation rates, it is a measure of how much vaccination reduces the chance that someone will need hospital, compared with having taken no vaccine at all.

The data at the time said that, if you’ve had two vaccine doses but no booster, you would be 52% less likely to require hospital due to Omicron compared with if you caught that variant and were unvaccinated.

UPDATE: A previous version of this article incorrectly concluded that the claim was ACCURATE based on based on a misinterpretation of data.

On 10 January 2022, the Chief Medical Officer for Northern Ireland, Professor Sir Michael McBride, was interviewed on BBC Radio Ulster’s The Nolan Show.

Presenter Stephen Nolan asked, “If you’ve had two doses [of the COVID-19 vaccine] and you haven’t had your booster, you’ve a 50-50 chance if you get Omicron of ending up in hospital, is that what you’re saying?”

McBride replied, “That’s correct.” He added, “What we do know is that two doses isn’t effective, and that the protection from hospitalisation drops to 70% at three months, and down to 50% at six months.”

The Department of Health told FactCheckNI that this was a case of a question being misinterpreted by the CMO during a live broadcast and not corrected while the show was still live.

Where do these figures come from?

During the interview, McBride referenced “data published on Friday by the UK Health Security Agency”. (The agency replaced Public Health England on 1 October 2021.)

He was referring to the weekly COVID-19 vaccine surveillance report published on 6 January 2022 (Week 1). Under “Vaccine effectiveness against the Omicron variant”, results for hospitalisations are presented for 18+ year olds (segments by age are not presented).

The data from early January (table below) suggest that there is vaccine effectiveness against hospitalisation for Omicron of 52% after a first dose, 72% at 2 to 24 weeks after a second dose, 52% at 25+ weeks after a second dose, and 88% at 2 or more weeks after a booster dose.

Table 1. Vaccine effectiveness against hospitalisation for Omicron (all vaccine brands combined). OR = odds ratio, HR = hazard ratio, VE = vaccine effectiveness, CI = Confidence interval.

What the data means

Vaccine effectiveness against hospitalisation is not a direct measure of hospitalisation rates – it is a measure of how much a vaccine reduces rates of hospitalisation.

UKHSA data says that, with two doses but no booster, vaccine effectiveness against hospitalisation is 52%.

This means there is a 52% lower risk of hospitalisation for those in that vaccine group (first two doses but no booster) compared with if they were unvaccinated.

It does not mean that there is a 50/50 chance (or a 48/52 chance) someone in that group will require hospital if they catch Omicron.

CORRECTION: A previous version of this article, published on 28 February 2022, incorrectly stated that the Chief Medical Officer’s claim was accurate. This is not the case and we were pleased to update the article on 1 March 2022.