The booster third dose continues to give high protection to people 65 and over, data suggests.
A fourth Covid jab is not yet needed, say UK experts, because booster doses continue to provide high protection against severe disease from the Omicron variant of Covid among older adults.
UK Health Security Agency data show three months after boosting, protection against hospitalisation remains at about 90% for people aged 65 and over.
Protection against mild symptomatic infection is more short-lived.
That drops to around 30% by about three months.
Figures also show why it is important to get a booster dose if you have only had two shots so far.
With just two vaccine doses, protection against severe disease drops to around 70% after three months and to 50% after six months.
The Joint Committee on Vaccination and Immunisation, which advises on vaccine policy, says the priority therefore remains to get first, second and third doses to those who have not already had them.
This is despite some countries such as Israel starting to give fourth Covid shots to manage the highly infectious Omicron variant that is causing rising numbers of infections around the globe.
More than 35 million boosters and third doses have now been administered across the UK.
Prof Wei Shen Lim, the JCVI’s chair of COVID-19 immunisation, said: “The current data show the booster dose is continuing to provide high levels of protection against severe disease, even for the most vulnerable older age groups.
“This is highly encouraging and emphasises the value of a booster jab.
“With Omicron continuing to spread widely, I encourage everyone to come forwards for their booster dose, or if unvaccinated, for their first two doses, to increase their protection against serious illness.”
Extremely vulnerable patients with impaired immune systems are still advised to have four shots overall, rather than the usual three, to be fully vaccinated.
But the JCVI says there is no immediate need to introduce a second booster dose, or fourth jab, to the most vulnerable care home residents and those aged over 80. The timing and need for further booster doses will continue to be reviewed as the data evolves.
Even though vaccines are working well, large numbers of infections still mean, unfortunately, some people will still get sick and need hospital care.
Health Secretary Sajid Javid says he is concerned by rising Covid hospital admissions, particularly in older age groups in this Omicron wave.
He said: “We are still seeing rising hospitalisations, particularly with the case rate rising with older age groups – that is of concern.
“And I think we have to be honest when we look at the NHS and say it will be a rocky few weeks ahead.”