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 among older adults.
UK Health Security Agency data shows 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 about 30% by about three months.
Figures also show why it is important to get a booster dose if you have only had two doses so far.
With just two vaccine doses, protection against severe disease drops to about 70% after three months and to 50% after six months.
The Joint Committee on Vaccination and Immunisation (JCVI), 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 chairman 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.”
‘Not the right time’
Professor Anthony Harnden, deputy chairman of the JCVI, said there would have to be swift action if data showed a drop off in immunity against severe disease for the elderly.
“But at the moment all the signs are good,” he told BBC Radio 4’s Today programme. “What isn’t sustainable in the long term is vaccine programme that delivers a vaccine every three months.”
He said it was important to get the timing right for any potential fourth dose of a vaccine for vulnerable people.
“Which may be later in the year… we just don’t think it’s the right time at the moment,” he said.
Meanwhile, extremely vulnerable patients with impaired immune systems are still advised to have four shots overall, rather than the usual three, to be fully vaccinated.
Even though vaccines are working well, large numbers of infections still mean some people will still get sick and need hospital care.
A psychology lecturer has told the BBC he believes varying coronavirus rules across the UK are causing people to feel “fatigue” and “uncertainty”.
Dr Simon Williams from Swansea University said: “When you’ve got different rules in different countries, but effectively we are still sharing the UK, it really hampers people’s understanding and it also undermines rules on both sides.”