Second shots of coronavirus vaccine could be delayed even further amid growing evidence that spacing out the doses improves their effectiveness.
The NHS vaccination programme aims to immunise about 14 million people at greatest risk of Covid by mid-February, with second doses to be given up to 12 weeks later.
But Public Health England’s head of immunisation, Mary Ramsay, told MPs on Wednesday that if infection data showed vulnerable groups, such as the over-80s, were well protected by their first shot, then second doses could be delayed to get a first jab to younger people as well.
The NHS originally planned to offer second shots of the Pfizer vaccine three weeks after the first, in line with the procedure in the trials, but the soaring infection rate forced a rethink in late December with the Joint Committee on Vaccination and Immunisation (JCVI) recommending first shots for as many people as possible in the highest-risk groups.
“Like we changed the schedule very quickly before Christmas, this is a very fast-moving field, and if more data emerges it may well be that the balance of those first doses, getting more first doses to people is a priority,” Ramsay told the Commons science committee. “If we’re seeing very high levels of protection, for example in the vulnerable groups, it may be more important to get more younger people vaccinated.”
Ramsay said Public Health England would review infection data weekly and that it may be possible to be “a little bit more relaxed” about the timing of second doses, depending on vaccine supply and the scientific evidence. Asked if second shots might be given beyond the current 12-week limit, she said: “That’s unlikely, but it’s always possible.”
Evidence now suggests that spacing out doses of the AstraZeneca/Oxford vaccine may be more effective at protecting people. Clinical trials revealed the efficacy of the vaccine was substantially higher, at 90%, in a subgroup of people who received half a dose followed by a full dose, rather than two full doses, which had an efficacy of 62%.
But Prof Wei Shen Lim, the chair of the Covid-19 immunisation group of the JCVI, told MPs further analysis by AstraZeneca showed the improved protection came from spacing out the doses.
“People who had the half dose then full dose were those who were vaccinated at a longer time interval, roughly six to 12 weeks, and what they’ve seen in their data is that people who have the second dose later probably have a three times higher antibody level than those who were vaccinated earlier. So if anything, it suggests that increasing the dose interval is beneficial,” he said.
Sir Mene Pangalos, the executive vice-president of biopharmaceuticals research and development at AstraZeneca, told the committee the first vaccine shot was more protective over time.
“What we’re seeing with our data so far is that as you go to the eight- to 12-week interval, you actually increase vaccine efficacy. People are protected enough with the first dose, to around 70%, but we see that within that eight- to 12-week interval is actually the sweet spot,” he said.