Covid-19 vaccines are still offering good protection against serious illness, which is the “main objective”, according to an expert who is advising the Government on a potential autumn booster campaign.
Professor Adam Finn, member of the Joint Committee on Vaccination and Immunisation (JCVI), said that while studies are showing waning immunity against mild illness some months after vaccination, the jabs are still warding off serious disease and hospital admissions.
The JCVI is expected to make an announcement in days on whether the UK will press ahead with an autumn booster campaign for 30 million people over the age of 50 and the clinically vulnerable.
The NHS in England has been preparing for such a push to commence on September 6, alongside its annual flu campaign.
But experts advising ministers on vaccination strategy are yet to confirm whether a third jab is needed.
On Wednesday a study concluded that the protection provided by two doses of the Pfizer/BioNTech and the Oxford/AstraZeneca coronavirus vaccines starts to wane within six months.
Scientists behind the Zoe Covid Study app said that the Pfizer jab was 88% effective at preventing Covid-19 infection a month after the second dose but after five to six months the protection decreased to 74%.
With the AstraZeneca vaccine, there was a protection against infection of 77% one month after the second dose but after four to five months, protection decreased to 67%.
Asked about the study, Prof Finn told BBC Radio 4’s Today programme: “I think the Zoe study, and a couple of other studies we recently had, do show the beginnings of a drop off of protection against asymptomatic or mildly symptomatic disease.
“But other studies are showing maintenance of good protection against serious illness and hospitalisation.
“So that’s encouraging actually that people who’ve had two doses are still very much well protected against serious illness, which is our main objective.
“But we do need to watch out very carefully to see if this waning begins to translate into occurrence of more severe cases because then boosters will be needed.”
Prof Finn, from the University of Bristol, also said that giving immunocompromised people a third dose of a coronavirus vaccine could give them better protection.
It comes after a separate study found that 40% of people who are immunosuppressed – either through medical treatment or by disease – generated a lower antibody response compared with healthy adults.
And 11% had an “undetectable” amount of antibodies four weeks after being doubled-jabbed, according to a study from the Universities of Glasgow and Birmingham.
Prof Finn said that offering a third jab to people who have impaired immunity shouldn’t be seen as a booster but an attempt to “get them to be protected or better protected than they already are with the two doses”.
He told the Today programme: “I think it’s very much what we expected, but it is very useful because we need to figure out who are the priority people to receive additional doses of vaccine.
“In this case it would be more a sort of third priming dose than the booster, in the sense that we’d be trying to get them to be protected or better protected than they already are with the two doses they’ve already had.”
He added: “The immunocompromised groups, which are the subject of this study… one would expect to be in line for an additional dose.
“I don’t really think of this as a booster because we’re still trying to get them protected in the first place.”
Prof Finn said there were a small group for whom the coronavirus vaccine would be “unlikely ever to work”.
But he said that the study showed that a lot of immunocompromised people “do have the capacity to make a response, albeit slightly less”.
“The fact that they can make a response at all means that they probably could be protected better by giving them an additional dose,” he said.
“This is very encouraging, that giving an additional dose to these groups would actually serve some useful purpose.”
On elderly people, he added: “I mean they are both the people who receive vaccine earliest, and probably the people whose immunity is most likely to wane.
“So, as evidence accumulates we may well find ourselves moving in that direction as well.”
The Government has said a further 174 people had died within 28 days of testing positive for Covid-19 as of Tuesday, bringing the UK total to 131,854.
It is the highest reported daily death toll since March 12, although the figures are likely to include a lag in reporting over the weekend.
Separate figures published by the Office for National Statistics show there have been 156,000 deaths registered in the UK where Covid-19 was mentioned on the death certificate.
As of 9am on Tuesday, there had been a further 30,838 lab-confirmed Covid-19 cases in the UK, the Government said.
It comes as the Welsh Government announced that children in the country have been removed from the so-called shielding list.
It said the move follows advice from the four chief medical officers of the UK.
Devolved departments of health in other nations have been contacted to see whether children will also be taken off the lists in England, Scotland and Northern Ireland.