COVID ANTIBODIES: Booster jabs linked to jump in Covid-19 antibodies among elderly
COVID ANTIBODIES: Booster doses of vaccine have helped increase the level of Covid-19 antibodies among people in older age groups in the UK, new analysis suggests.
Some 95.8% of over-80s in England were likely to have tested positive for antibodies in the week to November 7, up from 87.9% a month earlier, with 75-79 year-olds seeing a jump from 86.9% to 95.8% in the same period.
Similar trends are evident in Scotland, Wales and Northern Ireland, according to the Office for National Statistics (ONS).
The increase follows several months in which antibody levels had dropped slightly for most older age groups.
The presence of coronavirus antibodies suggests someone has had the infection in the past or has been vaccinated.
It takes between two and three weeks after infection or vaccination for the body to make enough antibodies to fight the virus.
Antibodies then remain in the blood at low levels, although these levels can decline over time to the point where tests can no longer detect them.
The latest estimates are a snapshot of antibody levels roughly six weeks after vaccine boosters began to be rolled out across the UK.
Boosters were initially offered to all over-50s who were six months on from their second dose of vaccine – meaning many of those who first received the extra jab were likely to have been elderly people who had been double-jabbed early in the year.
The ONS said there is a “clear pattern” between vaccination and testing positive for Covid-19 antibodies, but “the detection of antibodies alone is not a precise measure of the immunity protection given by vaccination”.
The recent rise in antibody levels among older age groups was though “likely a result of the vaccination booster programme”.
In Wales, 91.3% of over-80s were estimated to have Covid-19 antibodies in the week to November 7, up from 76.1% in the week to October 3, while in Scotland the figure was estimated at 92.3%, up from 78.4%.
For 75-79 year-olds, the figure for Wales has risen from 81.7% to 93.5% and for Scotland it has jumped from 81.8% to 93.5%.
For Northern Ireland, the ONS uses larger age groups because of a smaller sample size, and estimated antibody levels among over-70s were likely to be 89.7% in the week to November 7, up from 84.7% a month earlier.
All figures are based on a sample of blood test results from people in private households and do not include settings such as hospitals and care homes.
Antibody positivity is defined by a fixed concentration of antibodies in the blood.
Most people who are vaccinated will retain higher antibody levels than before they had the jabs but may have a lower number of antibodies at the time of testing.
This does not mean that these people have no protection against new infection, the ONS added.
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