Covid-19 antibody levels among older age groups have jumped in recent months and are now well above levels for under-50s, new figures suggest.

Some 96.3% of people aged 80 and over in England were likely to have antibodies at the start of December 2022, up from 89.2% in early September.

For 75 to 79-year-olds, the proportion stands at 95.8%, up from 87.4%.

There has been an even bigger jump for 70 to 74-year-olds, with levels increasing over the three months from 64.5% to 95.2%.

The figures are “likely a result of the vaccination booster campaign”, according to the Office for National Statistics (ONS), which has published the data.

The campaign was launched at the beginning of September and offered a fresh dose of vaccine to key groups of the population, starting with over-75s, frontline healthcare workers and people with a weakened immune system.

Doses were then offered to carers, pregnant women and everyone aged 50 and over.

But most under-50s were not eligible for an extra jab – and this is reflected in the latest antibody estimates, which show a large gap has opened up between older age groups and younger people.

Just 67.7% of 35 to 49-year-olds in England were likely to have Covid-19 antibodies at the start of December.

This is well below the estimates for age groups over 50, which are all either above or slightly below 90%.

Antibody levels among 35 to 49-year-olds have also fallen in recent months, having stood at 73.9% at the start of September.

The 35-49 age group now has the lowest estimated level of antibodies in England, below all older groups plus those aged 25-34 (71.9%) and 16-24 (75.1%).

This is likely to reflect the length of time since 35 to 49-year-olds last received a dose of vaccine, which could be up to a year or longer.

All estimates are for antibodies at or above 800 nanograms per millilitre, which is the primary threshold used by the ONS.

The figures do not cover the weeks immediately before Christmas 2022, when Covid-19 was becoming more prevalent and antibody levels will have risen among infected people.

It takes between two and three weeks after infection – or vaccination – for the human body to make enough antibodies to fight coronavirus.

Levels are expected to decrease over time, especially when exposure to the virus is reduced.

This is because our bodies stop making antibodies when they are not needed.

All ONS estimates are based on a sample of blood test results from people in private households and are subject to uncertainty, given they are based on samples that are part of the wider population.