The Health Service is bracing for a new wave of COVID in the weeks to come, while hospitals are struggling with their staffing issues.
Health experts warn that Omicron's BA-4 and BA-5 variants are spreading rapidly.
Data from Israel, which started giving the fourth dose at the start of the year, show the injection provided increased protection from COVID-19 transmission for about a month, and still provided greater protection against severe illness after that.
