The Oxford/AstraZeneca COVID-19 vaccine gives better protection the longer is left before a second dose, a government immunisation adviser has said.
Professor Anthony Harnden, deputy chair of the Joint Committee on Vaccination and Immunisation (JCVI), said data supports a delayed second dose of the Oxford jab, but that “we’re not so sure” about Pfizer's rival vaccine.
Both vaccines require two doses, and experts have recommended the second dose be given between four and 12 weeks after the first.
But Pfizer said its trials had not examined this length of delay – its researchers examined a three-week interval between jabs.
Watch: Oxford jab more effective when second dose delayed
Prof Harnden told the Commons science and technology committee: “What was really interesting with the Oxford/AstraZeneca data, was the longer that we left the second dose, the better the longer-term protection that you got from the vaccine.
“Not only that the Oxford/AstraZeneca trial data was really quite impressive in terms of protection against really severe disease, hospitalisation and death – in fact some of the data suggested it is up to 100% effective in that.
“So we were really quite confident that this is not only going to protect severe disease but as a longer-term strategy for those individuals that they may end up getting better long-term protection from a delayed second dose.
“We’re not so sure about that with Pfizer, I must say that we are sure, but we are much more sure about the Oxford/AstraZeneca vaccine.”
Two UK studies released Monday showed that COVID-19 vaccination programmes are contributing to a sharp drop in hospitalisations, boosting hopes that the shots will work as well in the real world as they have in carefully controlled studies.
Preliminary results from a study in Scotland found that the Pfizer vaccine reduced hospital admissions by up to 85% four weeks after the first dose.
In comparison, the Oxford shot cut admissions by up to 94%.
In England, preliminary data from a study of healthcare workers showed the Pfizer vaccine reduced the risk of catching COVID-19 by 70% after one dose, a figure that rose to 85% after the second.
Health secretary Matt Hancock said: “This new evidence shows that the jab protects you, and protects those around you.
“It is important that we see as much evidence as possible on the vaccine’s impact on protection and on transmission and we will continue to publish evidence as we gather it.’’
While no figure was given for how effective the Pfizer vaccine is at cutting transmission of the virus, researchers behind the healthcare study said it would cut transmission.
In December, experts advising the government, including the JCVI, said the second dose of vaccines should be delayed by up to 12 weeks, allowing more people to be vaccinated.
On Sunday, the government said every adult in the country should get a first vaccine shot by 31 July, at least a month earlier than its previous target.
The new target also calls for everyone 50 and over and those with an underlying health condition to get their first of two vaccine shots by 15 April, rather than the previous date of 1 May.
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