About 16 million people have had a booster vaccine or a third dose across the UK. Everyone aged 40 and over and the clinically extremely vulnerable are eligible to get a booster six months after their second jab. “If you’re yet to get your first, second or booster dose, please do come forward for the jab as soon as possible,” said Maggie Throup, the vaccines minister.
Research has previously shown that two weeks after a booster people have a very high level of protection from getting a symptomatic case of Covid.
The findings, based on a study of 80,000 people in Israel, showed that the chances of a breakthrough infection was roughly double by four months after the second dose of Pfizer/BioNTech and had increased more than tenfold by six months.
It comes as new research today shows immunity against infection falls significantly in the six months after two doses of the Pfizer/BioNTech vaccine. Experts say the major study highlights the importance of boosters.
The fresh warning comes after cases broke records in parts of Europe on Wednesday, with the continent once again the centre of a pandemic that has prompted new restrictions.
A Department of Health and Social Care spokesperson added: “People who have had their booster vaccine by 11 December will have very high protection against Covid by Christmas Day. Following a rise in cases and a return of lockdown restrictions in Europe, those eligible for a booster have been urged to take up the offer as soon as possible to protect themselves and their families, and help to reduce the pressure on the NHS.”
Previous work has shown that vaccines are highly effective at preventing hospitalisations for at least six months but that protection against infection falls more steeply, meaning that booster programmes are required to prevent the spread of infection.
Ariel Israel of Leumit Health Services, who led the research, said: “The message is that boosters are needed after about five months.”
The study, published in the British Medical Journal, is based on the electronic health records of just over 80,000 people who had a PCR test between mid-May and September at least three weeks after their second vaccination. None of the people in the sample had evidence of previous Covid-19 infection. The study found that the rate of positive results was found to rise in line with the time since people had had their second dose. Across all age groups, 1.3% of people tested positive 21-89 days after a second dose, but this increased to 2.4% after 90-119 days; 4.6% after 120-149 days; 10.3% after 150-179 days; and 15.5% after 180 days or more.
The authors said it appears clear that immunity wanes after the first three months of being double-vaccinated but returns to a high level after a booster dose. They said: “Large-scale Covid-19 vaccination campaigns can achieve control over the spread of the virus, but even in countries with high vaccination rates, breakthrough infections can occur. The risk of [Covid] infection in adults who received two vaccine injections increased with time elapsed since vaccination compared with the reference [individuals vaccinated in the last 90 days].”
They said it was too early to say whether immunity also wanes after a third booster dose. AstraZeneca has said antibody protection from its vaccine also wanes, although its chief executive, Pascal Soriot, said on Tuesday that the jab is thought to offer long-term T-cell immunity for older people, which could be better than other vaccines.